INTRODUCTION — Some treatments for malignancy, medical disorders, or gender affirmation can permanently end reproductive function. Patients considering such therapies should be rapidly referred for counseling regarding options for fertility preservation. Established cryopreservation techniques to preserve fertility include freezing of embryos and gametes. With appropriate pretreatment planning and intervention, future biologic parenthood is possible.
This topic will provide an overview of cryopreservation techniques. For the purposes of this discussion, the terms "female" and "woman" refer to any patient who has female reproductive organs and the potential to be pregnant. Similarly, the terms "male" and "man" refer to patients with male reproductive organs. Clinicians should also consider the fertility preservation needs of transgender and gender nonbinary persons.
An overview of fertility preservation, the approach to fertility preservation in healthy women who wish to delay childbearing, and the fertility treatments themselves are discussed separately.
●(See "Fertility preservation for deferred childbearing for nonmedical indications".)
●(See "Overview of ovulation induction".)
●(See "In vitro fertilization: Overview of clinical issues and questions".)
In this topic, when discussing study results, we will use the terms "woman/en" or "patient(s)" as they are used in the studies presented. However, we encourage the reader to consider the specific counseling and treatment needs of transgender and gender diverse individuals.
CANDIDATES — Any patient who is considering gonadotoxic therapy or surgery and who wishes to preserve future fertility is a candidate for cryopreservation techniques.
●Conventional candidates – Postpubertal children and adults with cancer or medical diseases (table 1) that require gonadotoxic therapy (table 2) have traditionally been referred for a fertility preservation consultation.
●Additional candidates – Additional candidates include patients undergoing gonad extirpation as part of gender affirmation surgery, those undergoing gonadal surgery, those with genetic and metabolic disorders that result in premature gonadal failure for benign lesions, or prepubertal children.
●BRCA gene mutation carriers – Studies of BRCA gene mutation carriers suggest these women experience accelerated ovarian aging [1-4]. A recent individual patient data meta-analysis covering >80 percent of all published data on women affected with breast cancer showed that women with BRCA mutations, particularly of the BRCA 1 type, have approximately 25 percent lower serum anti-Müllerian hormone (AMH) levels compared with mutation-negative controls [5]. Women with BRCA mutations have been reported to lose primordial follicles and accumulate DNA damage in their oocytes at an accelerated rate compared with controls [6,7]. Given that gonadotoxic chemotherapy damages oocytes by inducing DNA damage, BRCA mutation carriers may be more likely to lose their ovarian reserve after cancer treatments. A study of 108 women reported that those with BRCA 1 and BRCA 2 mutations had lower serum AMH levels following recovery after breast cancer chemotherapy compared with controls [8]. Both because of accelerated follicle loss and the risk of loss of fertility due to breast/ovarian cancer development and its associated gonadotoxic chemotherapy, women with BRCA mutations should have ovarian reserve assessment and be counselled about early childbearing and/or options for fertility preservation.
PRETREATMENT — Pretreatment involves procedures to obtain the cells, and potentially create the embryos, that will then be cryopreserved for future use. Typical procedures include ovarian stimulation and oocyte retrieval, semen or sperm collection, and in vitro fertilization (IVF).
Oocyte retrieval
Ovarian stimulation — Patients wishing to cryopreserve oocytes or create embryos first undergo controlled ovarian stimulation and oocyte retrieval. Timing of stimulation to the menstrual cycle is no longer required [9,10]. The preferred ovarian stimulation protocol is the one most compatible with the patient's medical condition(s), timing, and treatment needs. (See "In vitro fertilization: Procedure", section on 'Ovarian stimulation'.)
Although oocytes can be retrieved during a natural cycle, the yield is low; hence, controlled ovarian stimulation is the preferred approach [11]. An approximate 12 to 16 day interval is adequate to complete a cycle of ovarian stimulation and egg retrieval in most patients [12]. Prompt referral to a reproductive endocrinologist may also allow time for two cycles, which typically increases the number of retrieved oocytes.
Patients who are not candidates for ovarian stimulation are counseled about the options of donor oocytes, donor embryos, gestational carriers, and adoption. (See "Fertility and reproductive hormone preservation: Overview of care prior to gonadotoxic therapy or surgery", section on 'Other methods to preserve or restore fertility'.)
We do not advise ovarian stimulation after chemotherapy has been initiated because the ovarian response to ovarian stimulation, likelihood of cycle cancellation, and the quality of oocytes retrieved diminish with every round of chemotherapy, including the first [13-16]. Chemotherapy induces DNA double-strand breaks in human oocytes [17] and activates apoptotic death pathways [18]. Because of this, we and others advise women who receive chemotherapy to wait six months before attempting to conceive [19], although embryo banking between induction and consolidation chemotherapy has been reported in women with leukemia [20]. Waiting six months should allow developing follicles with DNA damage to be cleared from the ovary as new follicles are recruited from surviving primordial follicles.
Patients with estrogen-sensitive cancer — Most breast cancer chemotherapy regimens, except tamoxifen-only protocols, are gonadotoxic to ovarian reserve and warrant discussion of fertility preservation [21]. Concerns have been raised about using traditional ovarian stimulation techniques in patients with estrogen-sensitive cancers because traditional protocols result in supraphysiologic estrogen levels (up to 10-fold greater), which could stimulate cancer growth [22-24]. Estrogen-minimizing ovarian stimulation protocols have been devised, particularly for women with breast cancer [25]. The two most common agents used for controlled ovarian stimulation in these patients are letrozole and tamoxifen. Breast cancer patients who undergo ovarian stimulation with these agents do not appear to have an increased risk of disease recurrence or death, but data are limited [26,27]. At least one trial is underway to directly compare the efficacy of these treatments in women with breast cancer [28].
Letrozole — Letrozole, an aromatase inhibitor that is used in combination with gonadotropins, is the preferred stimulant for IVF cycles in women with breast cancer [29]. While pregnancy rates are impacted by patient age, type of cancer therapy, and partner factors, general pregnancy rates of 25 to 35 percent have been reported [30]. An advantage of ovarian stimulation with aromatase inhibitors is that peak estradiol levels are close to those observed in natural cycles [31,32]. (See "Ovulation induction with letrozole".)
We prefer a letrozole-follicle-stimulating hormone (FSH) protocol for ovarian stimulation in breast cancer patients undergoing IVF for embryo or oocyte cryopreservation because the combination results in low estradiol exposure and high oocyte recovery. In a prospective sequential cohort study comparing letrozole and anastrozole for ovarian stimulation in 54 patients with breast cancer, length of stimulation, total gonadotropin dose, number of follicles larger than 17 mm, and number of embryos cryopreserved were similar between the two groups [33]. However, the mean estradiol levels on the day of human chorionic gonadotropic (hCG) and post-hCG days were higher in the anastrozole group compared with the letrozole group. Anastrozole appears to result in significantly higher estradiol exposure than letrozole as it does not sufficiently suppress aromatase activity in the ovarian stimulation setting [33]. A meta-analysis demonstrated reassuring results with letrozole-gonadotropin ovarian stimulation regarding the number of retrieved MII oocytes, total number of oocytes, maturation rate, fertilization rate, and number of cryopreserved embryos [34]. Thus, we prefer letrozole-containing protocols, as above. Data on ovarian stimulation with other aromatase inhibitors are lacking.
The ovarian stimulation medications, including letrozole, can be started at a random time in the cycle without compromising fertilization rates, which has been referred to as "random start controlled ovarian stimulation" [9,10]. Studies have demonstrated a good safety profile with no increased risk of disease recurrence or decrease in survival, even for repeat cycles [35,36]. In a systematic review of 15 studies that evaluated mortality and recurrence after ovarian stimulation in women with early breast cancer, the relapse-free survival rates were similar among women with breast cancer who received ovarian stimulation with letrozole compared with women with breast cancer who did not undergo fertility preservation procedures [27]. The largest of the included studies reported recurrences in 6/120 women (5.0 percent) who received ovarian stimulation plus letrozole compared with 12/217 women (5.5 percent) who did not undergo ovarian stimulation (hazard ratio for recurrence 0.77, 95% CI 0.28-2.13).
Tamoxifen — Although tamoxifen, a selective estrogen receptor modulator with antiestrogenic actions on breast tissue, is as effective as clomiphene citrate in the treatment of anovulatory infertility and thus appears to be useful in women with breast cancer, we prefer using aromatase inhibitors combined with FSH over tamoxifen plus FSH because the oocyte yield is similar but the estrogen exposure is lower with letrozole-FSH [31,37]. However, in instances of contraindications to letrozole use (eg, drug sensitivity) or if the patient does not wish to stop long-term tamoxifen therapy, we use tamoxifen-FSH as an alternative regimen [38].
The utility of tamoxifen for ovarian stimulation in women with breast cancer was illustrated in a prospective study that examined the effectiveness and safety of tamoxifen for ovarian stimulation in breast cancer patients and then compared these results with a retrospective control group of breast cancer patients who had natural cycle IVF [39]. Patients stimulated with tamoxifen had fewer cancelled cycles (1/15 versus 4/9) and a higher number of mature oocytes (1.6±0.3 versus 0.7±0.2 in controls) and total embryos (1.6±0.3 versus 0.6±0.2 in controls). An embryo could be generated in 12 of 12 patients stimulated with tamoxifen; by contrast, natural cycle IVF resulted in embryos in only three of five patients. Although the peak estradiol levels were higher in the tamoxifen group than in unstimulated controls, cancer recurrence rates were not increased after a mean follow-up of approximately two years [31]. Others have reported no increase in breast cancer recurrence up to 10 years after coadministration of tamoxifen and conventional controlled ovarian stimulation for IVF [40].
Studies directly comparing tamoxifen with letrozole in this population are small.
●In one prospective study that compared the oocyte yield among women using tamoxifen alone (n = 12), those using FSH combined with tamoxifen (n = 7), and women using FSH combined with letrozole (n = 11), there was no significant difference in number of oocytes retrieved between the letrozole-FSH and tamoxifen-FSH groups [31].
●A different trial reported similar mature oocyte yield between the tamoxifen-gonadotropin (45 patients) and letrozole-gonadotropin (51 patients) groups (12±8.6 versus 11.6±7.5) [41].
●A randomized open-label trial has been registered to compare ovarian stimulation plus tamoxifen and ovarian stimulation plus letrozole with standard ovarian stimulation for fertility preservation in breast cancer patients [28].
Options for women who cannot undergo ovarian stimulation — When ovarian stimulation is not possible for time or safety issues, such as women with large or locally advanced breast cancers, harvesting of immature oocytes is an option [42]. One advantage of harvesting immature oocytes is that the procedure can be performed at any point in the menstrual cycle. Following retrieval, immature oocytes are cultured (in vitro maturation); mature oocytes are then cryopreserved. (See 'Oocytes' below.)
Sperm collection — Successful sperm collection after masturbation has been reported for boys aged 12 years and older [43-46]. In one study of over 4000 adolescents and young adults, successful sperm collection by masturbation was performed in 81 percent of 11 to 14 year olds, 91 percent in 15 to 17 year olds, and 95 percent in 18 to 20 year olds [43].
When no sperm are found in an ejaculate or if the patient is unable to ejaculate, sperm may be recovered by epididymal sperm aspiration or testicular sperm extraction (TESA) [47,48]. Patients who were previously considered sterile due to persistent postchemotherapy azoospermia may also benefit from TESA. In one study, sperm could be recovered by TESA performed by a microsurgical technique in 9 out of 20 patients who were rendered azoospermic due to prior chemotherapy [47]. Following intracytoplasmic sperm injection of the partner's oocytes, clinical pregnancy was achieved in three patients, resulting in term deliveries in two patients.
Transrectal electroejaculation may be utilized to collect sperm in patients who experience ejaculation problems secondary to previous surgical procedures or neurologic disease and possibly in pubertal boys unable to produce a sample through masturbation [49].
In vitro fertilization — Patients who desire only preservation of gametes go through the collection processes above and then stop short of using those gametes to create embryos. However, embryo cryopreservation was developed before oocyte cryopreservation and is a well-established technique. Embryo creation requires both oocyte and sperm. Use of donor gametes is an option if autologous ones are not available. These reproductive techniques are presented in detail separately.
●(See "In vitro fertilization: Overview of clinical issues and questions".)
●(See "Donor insemination".)
CRYOPRESERVATION — Established cryopreservation techniques include freezing of embryos, oocytes, ovarian tissue, and spermatozoa (table 3) [50,51]. Ovarian tissue cryopreservation is no longer considered investigational [52]. Cryopreservation of testicular tissue is available in some centers [53] and offered as part of a research protocol [50].
Freeze-thaw survival — There is no evidence to support that cryopreserved embryos, oocytes, or ovarian tissue deteriorates with long-term storage, and clinical experience demonstrates that they can be viably stored for decades. When slow freezing is used, frozen embryos survive the freeze-thaw process better than unfertilized oocytes (>90 percent survival versus 70 to 90 percent survival) [54,55].With the use of vitrification, survival rates of oocytes approach those of embryos [56]. Purely from the perspective of cumulative success rates, embryo cryopreservation may be preferable to oocyte cryopreservation when possible.
●Impact of fresh eggs – In some studies, blastocyst embryo formation rates were reported to be 50 percent higher with fresh eggs than frozen eggs [57]. Even with egg donation, clinical success rates are lower with frozen versus fresh eggs [58].
●Pregnancy versus live birth rates – A society guideline concluded that although there are no significant differences in per-transfer pregnancy rates with cryopreserved versus fresh donor oocytes, there is insufficient evidence that the live birth rate is the same with vitrified versus fresh donor oocytes.
●Neonatal outcomes – Neonatal outcomes appear similar with cryopreserved oocytes compared with fresh oocytes [59]. (See "Assisted reproductive technology: Infant and child outcomes".)
●Benefits of oocyte cryopreservation – Oocyte cryopreservation provides more flexibility for the female partner. As an example, a woman who donated her oocyte to create an embryo as part of a couple may no longer be able to use the resultant embryo if the relationship dissolves. Many centers are offering a combination of fertilizing some oocytes, creating embryos for cryopreservation, and simultaneously cryopreserving some mature oocytes to permit future flexibility.
However, it is important to discuss with patients that cryopreservation of embryos or oocytes does not guarantee preservation of fertility. Even if there is good survival, not all patients conceive and age-related increases in chromosomal abnormalities result from meiotic dysfunction in oocytes. To reduce the risk of chromosomal abnormality, the authors perform preimplantation genetic testing on embryos generated for fertility preservation purposes [60]. However, the feasibility of this approach in the setting of fertility preservation has not been evaluated in large scale studies.
Embryo — Cryopreservation of embryos is the most established technique for preserving reproductive capacity [61]; cryopreserved, thawed embryos are used in approximately 20 percent of all assisted reproductive technology cycles [62]. Live birth rates following frozen embryo transfer in infertile patients under the age of 35 approach 45 percent [63]. Success rates may be higher in fertility preservation patients who do not have preexisting conditions affecting fertility [64]. (See "In vitro fertilization: Overview of clinical issues and questions", section on 'Live birth and IVF'.)
Cryopreservation of embryos may not be technically feasible for every patient planning gonadotoxic therapy for several reasons:
●Time constraints – Since gonadotoxic treatment is usually implemented quickly after cancer diagnosis, there may not be adequate time for ovarian stimulation and oocyte retrieval, which usually requires a minimum of two weeks. Options to minimize the amount of time required include retrieval of immature oocytes followed by in vitro maturation or use of random-start ovarian stimulation protocols [9,65-68]. (See 'Options for women who cannot undergo ovarian stimulation' above and 'Letrozole' above.)
●No partner – Embryo preservation can be used by women with an available male partner or who elect to use donor sperm to create embryos rather than egg freezing.
●Legal and ethical issues – Ovarian stimulation for embryo freezing may not be ethically acceptable in postmenarchal children with cancer. Some couples may be philosophically opposed to cryopreservation of embryos, and this is only performed under strictly controlled embryo protection laws. It is illegal in some countries (eg, Germany, Switzerland, Italy).
●Estrogen-sensitive tumors – Estrogen-sensitive tumors might be stimulated by the high estrogen levels resulting from ovarian stimulation. (See 'Patients with estrogen-sensitive cancer' above.)
Oocytes
Mature oocytes — Cryopreservation of mature oocytes is an option for women without partners, women who may have partners but are concerned about the practical limitations with embryo cryopreservation, or women who opt not to use donor sperm for in vitro fertilization (IVF). In contrast to cryopreservation of embryos and sperm, oocyte cryopreservation is technically more challenging since oocytes contain more water and thus are more sensitive to cryoinjury from formation of ice crystals [69]. The meiotic spindle, cytoskeleton, cortical granules, and zona pellucidae are the structures particularly at risk from freezing. However, by using special freezing techniques, approximately 70 percent of cryopreserved oocytes survive the freeze-thaw process [70,71] and possibly as many as 90 percent with newest protocols [72,73].
In randomized trials, the pregnancy rate with cryopreserved/warmed mature oocytes was generally similar to that with fresh oocytes, although these trials were largely limited to donor oocyte populations and infertile couples with supernumerary oocytes [57,74-77]. Two large observational studies reported acceptable success rates but lower than with fresh oocytes [78,79]. Oocyte cryopreservation is no longer considered investigational.
The two methods of cryopreservation are the "slow-freeze" technique and vitrification (conversion of water to a solid without formation of ice crystals by using a very "fast freeze" and cryoprotectants). Vitrification is now the preferred method as it results in higher survival, implantation, and pregnancy rates compared with slow freezing [56,80,81]. The authors have created an online tool that may be useful for counseling women regarding likelihood of successful egg freezing [82].
There is a theoretical concern that damage to the metaphase spindle of the oocyte during oocyte cryopreservation could increase the risk of karyotypic abnormalities in offspring. Such defects have not been demonstrated in clinical studies, but experience is limited. The authors have demonstrated the feasibility of transvaginal oocyte retrieval and cryopreservation in young adolescent girls with cancer and mosaic Turner syndrome [83-85]. In young adolescent cancer patients or patients with sociocultural concerns regarding virginity, abdominal retrieval of oocytes following ovarian stimulation has also been offered [86]. The American Society for Reproductive Medicine has published guidelines for informed consent prior to elective oocyte cryopreservation [87].
Immature oocytes — Immature oocytes have been harvested from both in situ and excised ovarian tissue [88-90]. Development of the technique and assessment of its role in fertility treatment are ongoing [91]. The immature oocytes are matured in vitro (ie, in vitro maturation [IVM]) either before freezing or after thawing [92]; however, fresh oocytes have higher IVM rates than frozen oocytes [93-95]. A study questioned the utility of performing IVM in very young premenarchal girls because IVM rates were particularly low for girls younger than four years of age [96]. However, further studies are required to confirm this conclusion, as the authors' unpublished experience differs with that report.
Compared with conventional ovarian stimulation and retrieval of mature oocytes, advantages include the avoidance of large doses of gonadotropins and their associated risks and high costs, as well as avoidance of time constraints and exposure of estrogen-sensitive tumors to high estrogen levels [97]. In addition, immature oocytes are expected to be more resistant to cryoinjury than mature oocytes since they do not contain a metaphase spindle.
However, the implantation rate per embryo transferred (5.5 to 21.6 percent) is significantly lower, and early pregnancy loss per embryo transferred is higher than in conventional IVF [98]. The success rates of IVM in women with polycystic ovarian morphology with the use of follicle-stimulating hormone (FSH) priming is much higher compared with women having a regular menstrual cycle (implantation rates 47.7 and 11.8 percent, respectively) [99]. Reliable data on the success of IVM in a fertility preservation population are lacking. However, in women with breast cancer undergoing ovarian stimulation with the letrozole-FSH protocol, the authors reported higher than expected IVM rates [100]. Few pregnancies from frozen-thawed immature human oocytes have been reported, and, although follow-up studies of these children are limited, their results have been reassuring [101-103].
Ovary — This technique has the advantage of restoring ovarian endocrine function as well as the ability to conceive [29]. Cryopreservation of ovarian tissue is not an option for women with ovarian cancer or those at high risk of developing ovarian cancer.
Whole ovary and pedicle — Cryopreserving the entire ovary with its vascular supply might help decrease the degree of follicle loss during the initial ischemia period after transplantation, but it has been difficult to preserve both the ovarian follicles and ovarian vascular pedicle [104-108]. Techniques that efficiently cryopreserve both the ovary and its vascular pedicle have not yet been developed.
Ovarian tissue — With ever-increasing success rates following the transplantation of cryopreserved ovarian tissue and with its unique advantage of restoration of ovarian endocrine function, this technique is considered an established method of fertility preservation [29,52].
Procedure
●Techniques – While ovarian tissue cryopreservation followed by autotransplantation has been considered as an investigational method in general, orthotopic ovarian transplantation (eg, to remaining ovarian tissue or pelvic peritoneum) is now considered a standard clinical technique in several countries [52,59]. After initial controversy surrounding the success of the technique, the first ongoing pregnancy following heterotopic grafting of cryopreserved ovarian tissue was reported in 2013 [109-116].
Cryopreservation of ovarian tissue followed by heterotopic implantation (eg, in the abdominal wall, forearm, chest wall) remains an investigational approach, mainly because long-term outcome data are not as well established as for embryo cryopreservation [117,118]. In the authors' experience, heterotopic ovarian transplantation is more suitable when the primary goal is to restore hormone production and/or pelvic transplantation is not feasible for medical reasons. Even though the slow freezing method has been used as the standard technique to freeze ovarian fragments, some studies suggested the effectiveness and safety of vitrification [119,120]. However, clinical outcome data are limited with ovarian transplants using vitrified tissue, and further data will be needed before vitrification can replace slow ovarian tissue freezing.
●Candidates – Potential candidates for ovarian tissue cryopreservation include patients who require immediate gonadotoxic treatment, those undergoing repeated ovarian surgeries for benign ovarian lesions, and prepubertal girls. When compared with embryo cryopreservation, advantages include that neither ovarian stimulation nor a partner are needed and that implanted ovarian tissue can continue to produce hormones.
When possible, ovarian tissue should be obtained before chemotherapy since ovarian reserve is diminished with each round of chemotherapy [121,122]. However in our clinical experience, when ovarian tissue is cryopreserved from patients <25 years of age, live births have been achieved even in women who were exposed to chemotherapy before tissue cryopreservation [123]. Each case should be individualized based on the patient's age, amount and type of prior chemotherapy exposure, and other available options.
●Combined techniques – In attempt to ensure future fertility, immature oocytes can be retrieved from the harvested ovarian tissue and frozen separately as an adjunct to ovarian tissue cryopreservation [88]. All egg-containing follicles are in the outer 1 millimeter of the ovary, so cryopreservation can be limited to only this strip of tissue. The combination of partial removal of ovarian tissue for ovarian cryopreservation followed by ovarian stimulation and cryopreservation of oocytes can improve the efficacy of fertility preservation without compromising the average number and quality of retrieved oocytes [124]. A subsequent study demonstrated that a higher mean number of oocytes was collected ex vivo from removed ovarian tissue in girls compared with adults, but the percentage of degenerated oocytes was significantly higher in girls [125].
Patient selection — Consensus is lacking on patient selection criteria; protocols can be more or less restrictive. One challenge is the relatively small number of patients in the available studies to inform practice.
●Edinburgh criteria – Edinburgh criteria are strict selection criteria that have been proposed for selecting candidates for ovarian cryopreservation [126,127]. These criteria limit the procedure to girls/women under age 35 with no children and with at least a 50 percent risk of ovarian failure after cancer therapy [128].
●Our approach – We do not adhere to such strict criteria as we believe there are many more variables that need to be considered in patient selection, including that ovarian reserve testing does not predict fertility, patients with children may desire additional children, and the fact that technology continues to advance [17,129,130]. Studies that inform our approach include:
•A case series that involved transplantation of ovarian cortical pieces sutured onto an extracellular matrix scaffold reported successful transplantation in six of seven patients and a total of seven live births across four patients [131]. Although six of the patients had been exposed to gonadotoxic chemotherapy prior to tissue cryopreservation, which would have made them ineligible based on strict selection criteria, endocrine function was restored in all cases with a significantly longer graft longevity compared with patients in a meta-analytic database, where incidence of prior exposure to chemotherapy was significantly lower.
•In our opinion, prior exposure to chemotherapy should not be considered a contraindication for ovarian tissue cryopreservation. This is especially true in younger patients where primordial follicle oocytes' ability to repair chemotherapy-induced DNA double strand breaks is higher than for older patients [4,18,132-134].
Outcomes
●Graft longevity – In a study assessing the impact of robot-assisted autologous cryopreserved ovarian tissue transplantation with the use of a neovascularizing extracellular matrix scaffold, the mean graft longevity (43.2 ± 23.6 with sensitivity analysis) trended longer than the meta-analytic mean (29.4 ± 22.7), even after matching age at cryopreservation. This difference was achieved despite the fact that a higher proportion of recipients had received gonadotoxic chemotherapy before tissue cryopreservation compared with the meta-analytic control [118,131]. These findings suggest that new transplantation approaches may improve graft longevity [135].
●Cumulative pregnancy and live birth rates – Ovarian tissue transplant has resulted in cumulative ongoing pregnancy and live birth rates of 25 to 37 percent [118,131]. Pregnancy rates vary by age of the patient at time of gamete cryopreservation, surgical experience and technique, and the patient's comorbid medical conditions.
•In a 2017 meta-analysis of 19 studies on OTT that included pregnancy-related outcomes, 309 OTTs resulted in 84 live born children and 8 ongoing pregnancies, for cumulative clinical pregnancy and composite pregnancy rates (live birth plus ongoing pregnancy) of 57.5 and 37.7 percent, respectively [118]. Sixty-four percent of patients experienced restored endocrine function. Approximately two-thirds (62.3 percent) of the patients conceived naturally. For comparison, IVF frozen-thawed embryo transfers results in live birth rates of 22 to 35 percent, depending on the age of the mother [136].
•An update of a meta-analysis identified 518 patients who received 631 autologous transplants with cryopreserved ovarian tissue that resulted in 141 livebirths (147 infants) and 11 ongoing pregnancies [118,131]. After excluding studies with inadequate data and patients who did not desire pregnancy, the calculated pregnancy rate was 25 percent per transplant (115 live births or ongoing pregnancies in 460 recipients) [131]. In a subgroup of seven patients who underwent robot-assisted ovarian tissue transplantation involving a neovascularizing extracellular matrix, all were able to attain gametes and a total of seven babies have been born to four of the patients.
●Negative impact of increasing patient age – Similar to conventional conception or IVF, increasing patient age at the time of ovarian tissue cryopreservation is associated with reduced live birth rates. In a registry study including 244 transplantations in 196 patients, the live birth rate dropped from 29.2 percent (95% CI 20.9-36.3) for patients <35 years to 16.7 percent (95% CI 7.9-29.3) for patients ≥35 years [137]. The majority of pregnancies after ovarian tissue graft have occurred in patients who were younger than 30 years old at the time of the cryopreservation procedure, including a postpubertal but premenarchal girl and a prepubertal girl [138-141]. Moreover, the pregnancy rate was higher after the first transplantation (30.6 percent [95% CI, 24.2-37.6]) compared with the second and subsequent transplantations (11.8 percent [95% CI, 3.3-27.5]). (See "Advancing maternal age: Infertility evaluation and management", section on 'Biology of female fertility'.)
●Impact of menstrual patterns – In a review of data from five European centers, the live birth rate was reported as 30.6 percent (15 of 49) in women who had persistent irregular menses while undergoing OTT and 25.4 percent (54 of 212) in women who had amenorrhea before OTT [142].
Ovarian tissue transplant for patients with cancer — Ovarian tissue preservation may not be an ideal option for patients with ovarian cancer, those at high risk of developing ovarian or breast cancer, or those with blood malignancies (ie, leukemias) [29].
●Hereditary ovarian cancer syndromes – Patients with mutations in breast cancer susceptibility genes (BRCA1 or BRCA2) have significantly elevated lifetime risks of cancer (table 4). These women are offered prophylactic oophorectomy (usually at the completion of childbearing) to decrease the risk of developing ovarian cancer or as a part of a treatment plan for breast cancer [143]. They are not ideal candidates for cryopreservation of ovarian tissue, given their increased risk of developing ovarian cancer and the relatively high incidence of occult ovarian cancer (2.0 to 18.5 percent) in BRCA carriers. (See "Cancer risks and management of BRCA1/2 carriers without cancer".)
•Cancer transmission and potential risk reduction – We believe that patients with hereditary breast-ovarian cancer syndromes can safely undergo ovarian tissue preservation and transplantation by using strategies to limit risk of subsequent cancer transmission or development. Mitigation strategies include harvesting ovarian tissue at an early age when risk of ovarian cancer is negligible and then pausing potential cancer development with cryopreservation. At transplantation, the patient's ovarian cancer risk would then resume from a lower-risk biologic tissue age. However, these assumptions have not yet been tested in studies and not all experts agree. If ovarian tissue is cryopreserved for reimplantation, a detailed histologic analysis of the ovarian cortical pieces is mandatory but may not completely exclude the presence of ovarian cancer. (See "Risk-reducing salpingo-oophorectomy in patients at high risk of epithelial ovarian and fallopian tube cancer".)
•Reduced ovarian reserve – Another disadvantage for women with BRCA mutations is that they appear to have accelerated ovarian aging and lower ovarian reserve compared with those without the mutations. A individual data meta-analysis from five centers worldwide showed that serum AMH levels were approximately 25 percent lower in women with BRCA mutations who were affected with cancer, compared with those who did not carry these mutations [5]. The results were similar after adjustment for age, birth control pill use, the center, body mass index (BMI), and other factors.
●Breast cancer – Early stage infiltrative ductal breast cancer, the most common histologic subtype, rarely metastasizes to the ovaries, in contrast to lobular breast cancer, which usually occurs during later years of life [144].
●Other cancers – In women with cancer not involving the ovary, there is a theoretical concern of reimplantation of metastatic cells from the primary tumor during autotransplantation. However, the majority of the tumors encountered during reproductive ages have relatively low potential to metastasize to ovaries [145,146]. In the authors' series of 55 women with various malignancies undergoing ovarian tissue cryopreservation, no ovarian metastases were found on histologic analysis of tissue samples [147]. Exceptions include blood-borne malignancies, such as leukemias [148-151], as well as Burkitt lymphoma and neuroblastoma.
•Leukemia – Leukemia may not be a strict contraindication for ovarian tissue cryopreservation, as most of the candidates are in remission waiting for hematopoietic stem cell transplantation. In our and others' limited experience, no recurrence of leukemia has been observed after ovarian autotransplantation [152,153]. In a study of six patients with leukemia who had been treated with hemapoietic stem cell transplant, no cancer was detected during a median of 41 months of follow-up and ovarian function returned in all patients [154].
•Lymphoma – Animal studies indicate that the likelihood of ovarian involvement is not high in Hodgkin lymphoma, but the possibility of transmission cannot be excluded completely [155,156]. The only series in humans with lymphoma reported that none of the 26 patients had evidence of ovarian involvement by histology and immunohistochemistry [157].
Although cryopreservation procedures generally should not be performed for the purpose of future autotransplantation when there is a significant concern about cancer involving the ovaries, there are possible exceptions. Ovarian tissue cryopreservation can be offered in patients with no recourse even when the risk of cancer cell presence in the ovary is high, as long as the patient understands that the ovary will not be replaced until and unless a safer method of utilization of such tissue, such as the in vitro growth of primordial follicles, is developed. A thorough histologic evaluation should be done on portions of harvested ovarian tissue to rule out micrometastases prior to cryopreservation. If available, molecular markers can also be utilized to detect an extremely small number of metastatic cells in the tissue [149,158].
Transplantation after cryopreservation — For women who have undergone ovarian tissue, or theoretically whole ovary, cryopreservation for fertility preservation, the stored tissue is thawed and reimplanted (transplanted) at a future date following treatment. That tissue can be placed in the native location of the same patient (autologous orthotopic), a different anatomic location in the same patient (autologous heterotopic), or in a different individual (nonautologous).
●Autologous orthotopic OTT – Until it is technically possible to cryopreserve a whole ovary, ovarian cortex is cryopreserved in small strips. In the orthotopic technique, these thawed strips are transplanted to the remaining ovary, pelvic side wall, or mesosalpinx using laparoscopic or robot-assisted techniques [123]. The authors reconstruct the ovarian graft on a human extracellular matrix scaffold with a microsurgical approach before transplanting with a robot-assisted technique [123,159-161].
Although transplanted ovarian tissue has remained functional for close to ten years in rare patients, most patients experience a limited functional lifespan of the graft [162]. Thus, cryopreserved ovarian tissue is not autotransplanted until the woman is ready to conceive and has received medical clearance from her oncologist. It may take two to five months before the transplanted ovarian tissue begins to function. If additional cryopreserved ovarian tissue is available, a second heterotopic autotransplant can be performed if the initial ovarian transplant function wanes [163].
●Autologous heterotopic transplantation – The optimal site for heterotopic transplant of ovarian tissue is not known. Ovarian tissue has been placed in subcutaneous tissue of the forearm and lower abdomen [164,165]. The first ongoing pregnancy following heterotopic grafting of cryopreserved ovarian tissue was reported in a patient who had previously undergone bilateral oophorectomy for a granulosa cell tumor [116]. After transplantation of frozen-thawed ovarian tissue to her anterior abdominal wall, she underwent ovarian stimulation with retrieval of two oocytes followed by IVF with intracytoplasmic sperm injection.
In women planning to undergo radiation therapy to the pelvis, autotransplantation of a fresh ovary to the upper extremity with creation of vascular anastomosis would remove the ovary from the radiation field and thus protect it from radiation damage [166,167] (see "Fertility and reproductive hormone preservation: Overview of care prior to gonadotoxic therapy or surgery", section on 'Autotransplantation'). Ideally, the ovary would then continue to produce hormones and oocytes, which could be aspirated for IVF. However, studies suggest that the lifespan of autotransplanted ovarian grafts may be limited to less than three years, mainly owing to the loss of a substantial number of follicles during the ischemic period of the revascularization process immediately after transplantation [163,165,168,169].
In chemotherapy patients, autologous heterotopic transplantation of a fresh ovary or ovarian tissue would not be useful since the effects of chemotherapy are systemic. However, autologous heterotopic transplantation of cryopreserved ovarian tissue after chemotherapy could be an option in these patients.
Large clinical studies are needed to determine the true efficiency of the OTT procedure and to determine the optimal surgical technique [170,171].
●Nonautologous orthotopic transplantation – Nonautologous orthotopic transplantation is not a fertility preservation procedure; rather it has been proposed as infertility treatment for patients with primary ovarian insufficiency or who may have an identical twin [113]. Though live births have been reported following this approach, egg donation may be more practical then nonautologous ovarian transplantation because of two major disadvantages to this approach:
•When the ovarian tissue is removed from a donor, the donor may be put at higher risk of premature ovarian failure.
•Since an immunologically identical donor is needed, there are few potential candidates for this procedure.
Semen or spermatozoa — Cryopreservation of semen or spermatozoa is a well-established technique that should be offered to all postpubertal boys and adults undergoing gonadotoxic treatment [29,50].
Spermatozoa may be damaged by freezing and thawing [25]. Recovery of motile sperm after thawing is less likely in men with severe oligospermia and possibly those with testicular cancer or a basal semen parameter below the 5th percentile of the World Health Organization reference value [172].
Testicular tissue — Testicular tissue preservation and tissue grafting/reimplantation are techniques for fertility preservation, particularly in prepubertal boys [29,50]. While these procedures are offered in some countries, they are considered investigational in others.
RESOURCES FOR PATIENTS AND CLINICIANS
●Cancer.Net – A website for patients by the American Society of Clinical Oncology (ASCO)
●ReproductiveFacts.org – A website for patients by the American Society for Reproductive Medicine (ASRM)
●LIVESTRONG Fertility – Provides information on treatment and eligibility for discounted rates for fertility preservation interventions
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Female infertility".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topics (see "Patient education: Preserving fertility after cancer treatment in children (The Basics)" and "Patient education: Preserving fertility after cancer treatment in men (The Basics)" and "Patient education: Preserving fertility after cancer treatment in women (The Basics)")
SUMMARY AND RECOMMENDATIONS
●Candidates – Any reproductive-age patient considering gonadotoxic therapy or surgery and who wishes to preserve future fertility is a candidate for cryopreservation techniques. Postpubertal children and adults with cancer or medical diseases (table 1) that require gonadotoxic therapy (table 2) have traditionally been referred for a fertility consultation. Additional candidates include patients undergoing gonad extirpation as part of gender affirmation surgery, those undergoing gonadal surgery for benign lesions, or prepubertal children. (See 'Candidates' above.)
●Pretreatment procedures – Pretreatment involves procedures to obtain the cells, and potentially create the embryos, that will then be cryopreserved for future use. Typical procedures include ovarian stimulation and oocyte retrieval, semen or sperm collection, and in vitro fertilization (IVF). (See 'Pretreatment' above.)
●Established cryopreservation techniques – Established cryopreservation techniques now include freezing of embryos, oocytes, ovarian tissue, and spermatozoa (table 3). Cryopreservation of testicular tissue is available in some centers and offered only as part of a research protocol [53]. (See 'Cryopreservation' above.)
●Embryos – Embryo cryopreservation is the longest-used fertility preservation technique. However, it may not be medically feasible for all patients and not all patients have partners. (See 'Embryo' above.)
•Mature oocytes – Cryopreservation of mature oocytes is an option for women without partners, women who may have partners but are concerned about the practical limitations with embryo cryopreservation, or women who opt not to use donor sperm for IVF. Retrieval of immature oocytes followed by in vitro maturation has also been performed. Advantages include avoidance of large doses of gonadotropins and fewer time constraints. (See 'Oocytes' above.)
•Ovarian tissue– Cryopreservation of ovarian tissue is becoming more widely available. This technique has the advantage of restoring ovarian endocrine function as well as the ability to conceive. Cryopreservation of ovarian tissue is not an ideal option for women with ovarian cancer or those at high risk of developing ovarian cancer. (See 'Ovary' above.)
•Sperm – We offer cryopreservation of sperm to all postpubertal male cancer patients before starting cytotoxic therapy. (See 'Semen or spermatozoa' above.)
●Post-thaw survival – There is no evidence to support the statement that cryopreserved embryos, oocytes, or ovarian tissue deteriorates with long-term storage, and clinical experience demonstrates that they can be viably stored for decades. Frozen embryos survive the freeze-thaw process somewhat better than unfertilized oocytes (>90 percent survival versus over 70 percent survival). (See 'Freeze-thaw survival' above.)
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