Human oocyte and ovarian tissue cryopreservation and its application

PURPOSE: To review the recent progress in human oocyte and ovarian tissue cryopreservation, and in the application of these two technologies for preserving female fertility of patients who are undergoing cancer treatment. DESIGN: The literature on human oocyte and ovarian tissue freezing was searched with PubMed. The scientific background, current developments and potential future applications of these two methods were reviewed. RESULTS: Chemotherapy and/or radiotherapy can induce premature ovarian failure in most of female cancer patients. Consequently, there has been a greater need for options to preserve the reproductive potential of these individuals. However, options are somewhat limited currently, particularly following aggressive chemotherapy and/or radiotherapy treatment protocols. In recent years, there have been considerable advances in the cryopreservation of human oocytes and ovarian tissue. For women facing upcoming cancer therapies, cryopreservation of ovarian tissue and oocytes is a technology that holds promise for banking reproductive potential for the future. Recent laboratory modifications have resulted in improved oocyte survival, oocyte fertilization, and pregnancy rates from frozen-thawed oocytes in IVF. This suggests potential for clinical application. CONCLUSIONS: In the case of patients who are facing infertility due to cancer therapy, oocyte cryopreservation may be one of the few options available. Ovarian tissue cryopreservation can only be recommended as an experimental protocol in carefully selected patients. In ovarian tissue transplantation, more research is needed in order to enhance the revascularization process with the goal of reducing the follicular loss that takes place after tissue grafting. These technologies are still investigational, although tremendous progress has been made. The availability of such treatment will potentially lead to its demand not only from patients with cancer but also from healthy women who chose to postpone childbearing until later in life and therefore wish to retain their fertility.     

Present and future fertility preservation strategies for female cancer patients

As survival rates with cancer treatment are steadily increasing, many women are now facing sterility due to treatment induced ovarian failure. This review will attempt to summarize the options for trying to preserve fertility in these patients. The optimal approach depends on the type of cancer, the type of treatment (e.g., radiation and/or chemotherapy), time available till onset of treatment, patient's age, and whether the patient has a partner. Ovarian transposition remains the standard of care for women undergoing pelvic radiation, although it has been suggested that it may be combined with ovarian tissue cryopreservation. For patients about to receive chemotherapy or whole body radiation, in vitro fertilization (IVF) with embryo cryopreservation is a well established treatment with a good success rate. However, it requires delaying cancer treatment for 2 to 4 weeks and a partner or willingness to use donor sperm. When these criteria cannot be met, more experimental options include oocyte cryopreservation for later IVF and ovarian tissue cryopreservation. The tissue may be autotransplanted back to the pelvis, when the patient is in remission, to attempt spontaneous conception or subcutaneously for easy access of follicle aspiration for IVF. Alternatively, it may be xenografted to immunocompromised mice to induce follicle maturation in preparation for retrieval for IVF. Emerging treatment options for fertility preservation include medication to prevent chemotherapy-induced oocyte damage and oocyte construction from somatic cell nuclei. IVF with donor oocyte remains an established option with a very high success rate for those who fail to conceive with the above measures or who elect not to avail themselves to experimental procedures. TARGET AUDIENCE: Obstetricians & Gynecologists, Family Physicians. LEARNING OBJECTIVES: After completion of this article, the reader should be able to demonstrate knowledge about fertility preservation when counseling appropriate female cancer patients, recall current clinical strategies to assist women cancer patients to try to maintain their fertility if they wish, and appraise future strategies as they develop.     

Fertility preservation options for female patients with malignancies

PURPOSE OF REVIEW: Preservation of fertility in female patients diagnosed with cancer has recently been an area of intensive investigation. This review summarizes available options and discusses recently published data concerning experimental methods. Specific strategies for fertility preservation in women with gynecologic malignancies are also presented. RECENT FINDINGS: Success with ovarian stimulation protocols using tamoxifen or aromatase inhibitors has recently been reported for women with breast cancer who attempt embryo cryopreservation prior to chemotherapy. The first embryo transfer using oocytes retrieved from cryopreserved ovarian tissue implanted at a heterotopic location, the first pregnancy following orthotopic transplantation of cryopreserved ovarian tissue, and increasing success with oocyte cryopreservation were also reported. SUMMARY: Fertility preservation in female patients with cancer has become an important health issue due to increasing survival rates and delayed childbearing especially in Western countries. Radical vaginal trachelectomy for cervical cancer, conservative surgery for ovarian tumors, and progestin treatment in endometrial cancers may be considered at early stages in order to preserve fertility. Embryo cryopreservation is an established technique that is available for fertility preservation, providing a delay in the initiation of chemotherapy or radiotherapy is acceptable, and a partner or donor sperm is available. Additional techniques that could be offered after counseling the patient about their experimental nature include oocyte cryopreservation, ovarian cryopreservation, and gonadotropin-releasing hormone agonist co-treatment with chemotherapy. Improvement of these techniques as well as better characterization of their success rates and risks await further investigation.     

Preservation of female fertility during cancer treatment

Improvements in the success of cancer treatments have resulted in increased awareness of the long-term effects of treatment, of which gonadal failure is the most significant. Thus, preservation of fertility potential has become a major goal and could be realized by preventing ovarian toxicity or by cryopreservation of reproductive cells/tissues. This review aimed to critically discuss the current protocols for the management of chemotherapy-inducced/radiotherapy-induced premature ovarian failure (POF). A medical approach using the gonadotropin-releasing hormone analog (GnRHa) may act to protect the gonads during radiation and/or chemotherapy by preferentially steering cells into cell cycle arrest with a decline in responsibility to the chemotherapeutic agents. Ovarian protection by GnRHa cotreatment against chemotherapy can enable the preservation of future fertility in survivors and prevent the bone demineralization and osteoporosis associated with hypestrogenism and POF. In vitro fertilization of retrieved oocytes could enable embryo freezing in some patients. Embryo cryopreservation is considered standard practice and widely available, but may seldom be used because of a lack of a male partner, the need to postpone cancer therapy for a few weeks and the possibility that an estrogen rise may be undesirable in sensitive cancer patients. Improvement in oocyte cryopreservation may offer additional possibilities; the prolonged culture of primordial and primary follicles in vitro is still unfeasible. Currently, the cryopreservation of ovarian cortex, which hosts thousands of immature follicles, is an investigational method, but has the advantage of requiring neither a sperm donor nor ovarian stimulation. Fertility preservation is often possible in women undergoing cancer treatment. To preserve the full range of options, fertility preservation procedures should be considered as early as possible during therapy planning. (Reprod Med Biol 2008; 7 : 17–27)     

Quels sont actuellement les espoirs réels de grossesse après cryoconservation ovarienne ?

Survival rates for cancers that occur in childhood and adolescence have improved over the last decades, and preservation of future fertility in these patients has become a relevant issue. Premature ovarian failure is a consequence of exposing women to chemotherapeutic drugs and ionizing radiation. Ovarian cryopreservation is an alternative to cryopreservation of embryos or oocytes for theses patients. Ovarian cryopreservation aims to reimplant ovarian tissue after complete remission into the pelvic cavity (orthotopique site) or a heterotopic site like the abdominal wall or the forearm. In vitro folliculogenesis, that aims at the maturation of ovarian cortex primordial follicles cryopreserved for a FIV, is still in an experimental research stage. In this review, the objective was to evaluate the real hopes of pregnancy after ovarian cryopreservation. Indeed, many teams offer ovarian cryopreservation at present time, although only two pregnancies have been achieved to date. In both cases, it can be discussed whether the fertilized oocyte originated from the transplant or from the native ovary. Furthermore, the potential for reintroduction of cancerous cells may limit this technique in cancers that are known to have a risk of ovarian dissemination. The hopes engendered by ovarian cryopreservation, but also its limits, must be explained to the patients before an ovarian surgery for cryopreservation.     

Recent progress in oocyte and ovarian tissue cryopreservation and transplantation

Ovarian tissue cryopreservation and transplantation is an experimental technique that has been developed to sustain the reproductive function of women and children who are faced with sterilizing chemotherapy, radiotherapy, or radical reproductive surgery. Oocyte cryopreservation, on the other hand, is less feasible in the context of cancer because there is usually inadequate time to complete an ovarian stimulation cycle. The main promise of oocyte cryopreservation is that it offers an alternative when embryo freezing is not possible for technical, regulatory, or religious reasons. Oocyte freezing is more suitable for a single woman when the concern is age-related decline in fecundity. There have been significant scientific advances in the field of cryopreservation of ovarian tissue and oocytes, especially within the past few years. Ovarian function has been reported after the first cases of ovarian transplantation, and the number of pregnancies from cryopreserved oocytes has grown. Ovarian tissue and oocyte freezing can now be recommended in a carefully selected group of patients, provided that these options are offered under protocols that are approved by an institutional review board.     

Fertility Preservation in Reproductive Age Women with Cancer

Cancer may be detected at any age and could affect children, and reproductive age women as well. In recent years, cancer treatment has become less destructive and more specific. As a result, survival rates and quality of life following successful treatment have continuously improved. Cancer treatment typically involves surgery, chemo- or radiation therapy, or the combinations of these. These interventions often adversely affect the function of the reproductive organs. Chemo- and radiation therapy are known to be gonadotoxic. Survivors of oncologic therapy are typically rendered infertile primarily due to the loss of ovarian function. There are, however, several medical, surgical, and assisted reproductive technology options that could be and should be offered to those diagnosed with cancer and wish to maintain their fertility. Embryo cryopreservation has been available for decades and has been successfully applied for fertility preservation in women diagnosed with cancer. Recent advances in cryobiology have increased the efficacy of not just embryo but even oocyte and ovarian tissue freezing–thawing. Oocyte vitrification just like embryo cryopreservation requires the use of stimulation but does not require the patient to be in a stable relationship or accept the use of donor sperm. Ovarian tissue cryopreservation does not require stimulation and, following successful transplantation, provides the patient with the most eggs but is currently still considered experimental. This paper summarizes the various fertility-sparing medical, surgical and assisted reproductive technology options. It reviews the current status of embryo, oocyte, and ovarian tissue cryopreservation and discusses their risks and benefits.     

Technical and ethical challenges of fertility preservation in young cancer patients

As cancer treatment improves, more young men and women survive, but they suffer from infertility as a major sequel of cancer treatment. Gamete and embryo cryopreservation are the only options available to these patients for preserving their fertility. Although cryopreservation of spermatozoa and embryos are already established, oocyte banking is still experimental. The advent of testicular tissue cryopreservation and spermatogonial stem cell transplantation in men, and ovarian tissue cryopreservation and in-vitro follicular maturation in women, has started a frenzy of experiments worldwide trying to demonstrate their potential use in fertility preservation. Although major improvements have been made in tissue cryobanking in the past decade, there are still many unresolved technical issues related to these procedures. Furthermore, the intersection of cancer and fertility preservation in young patients raises ethical, legal and policy issues for oncologists and cancer survivors. Informed consent of minor patients, legal parentage and medical negligence claims are some of the potential legal challenges faced by society and healthcare providers. This review summarizes the technical and ethical challenges of gamete cryopreservation in young cancer patients.     

Fertility Preservation

Advances in early diagnosis and cancer treatment have allowed the quality of life postcancer treatment as a recognized issue, and efforts have been made to preserve the fertility potential. Radiotherapy and chemotherapy have detrimental effects on ovarian reserve. Well-established methods against radiotherapy-induced gonadotoxicity are pelvic shielding or removal of the ovaries from the radiation field. Gonadal toxicity of chemotherapy depends mainly on the type of treatment and patient??s age. In vitro fertilization (IVF) and embryo cryopreservation are the most commonly used procedures for females undergoing chemotherapy. Oocyte cryopreservation is a promising method and has the advantage of eliminating the contribution of a partner. Ovarian tissue cryopreservation is experimental and the only method for prepubertal girls. The trend toward delaying child-bearing results in increased prevalence of age-related infertility and has raised debates on social egg freezing in many countries. Fertility preservations options for different indications are discussed in the light of recent literature.     

Ovarian tissue cryopreservation--new opportunity to preserve fertility in female cancer patients

INTRODUCTION: Malignant disease and the therapy are major factors that may result in complete loss of fertility. There are several strategies for fertility preservation in fertile women faced with cancer. A modern and potentially effective method of reproductive function protection is ovarian tissue cryopreservation. MATERIALS AND METHODS: This paper summarizes the medical and scientific knowledge in this interesting multidisciplinary medical field. Furthermore, the authors' own experience with this novel and interesting method of ovarian tissue protection is presented. Ovarian tissue was obtained during laparoscopic surgery in five nuliparous women (aged 19-33) with a diagnosis of lymphoma before chemotherapy from 2004 to 2006. After laboratory preparation, tissue was frozen by a slow cooling technique and stored in liquid nitrogen. RESULTS: In total 75 women with malignant lymphoma before chemotherapy were referred to our center for consultation--68 chose ovarian inactivation by GnRH analogues during chemotherapy, two IVF cycles with embryo or oocyte cryopreservation and five ovarian tissue cryopreservation. In these five women one to two slices of ovarian cortex from both ovaries were recovered. Totally 20 cryotubes with three pieces of tissue in each were cryopreserved. In no case was metastasis of cancer cells found by histological evaluation. CONCLUSIONS: Cryopreservation of ovarian tissue represents an effective alternative or addition to the cryopreservation of embryos or oocytes for women at risk of premature ovarian failure due to chemotherapy. Reproductive function protection requires close cooperation between oncology departments and assisted reproduction centers.     

Kryokonservierung von Ovarialgewebe und Eizellen

Aggressive chemotherapy and radiotherapy often lead to infertility. Therefore, strategies for fertility preservation have been developed. These include the cryopreservation of unfertilized oocytes and cryopreservation of ovarian tissue. Cryopreservation of unfertilized oocytes is cryogenically more difficult than the cryopreservation of embryos, but for younger patients has the advantage that at the time of egg retrieval no male partner is needed. Recent studies have shown that for unfertilized eggs the vitrification method is preferable to slow freezing. However, a greater number of eggs can only be obtained after ovarian stimulation, which results in postponement of chemotherapy. In addition, the method is not suitable in prepubertal girls. Here and in order to avoid a delay of chemotherapy, cryopreservation of ovarian tissue could be offered. This is a simple and successful method, as was shown by the first live-births of children in Germany in 2011/2012. Even at the risk of contamination of the ovarian tissue with cancer cells that would prohibit a retransplantation, the cryopreservation of ovarian tissue is useful because new methods for in vitro maturation are likely able to help even these patients have their own children.     

Fertilitätserhalt bei Krebs

Survival rates of female cancer patients are improving steadily. Clinicians are increasingly confronted with the long-term effects of chemotherapy and radiotherapy on the fertility of young women. Premature ovarian failure in women who wish to become pregnant is devastating both for the patient and her partner. In the case of predictable loss of gonadal function due to a planned cancer treatment fertility preservation options should be offered to the patient. Current methods of fertility preservation include conventional reproductive techniques as well as GnRH analogue treatment, cryopreservation of oocytes and cryopreservation of ovarian tissue. Most of these techniques are still experimental and should only be decided after individual and patient-specific informed consent as well as interdisciplinary counselling.     

Y a-t-il une place pour la cryopréservation ovocytaire après le traitement du cancer ?

The number of young cancer women theoretically eligible for fertility preservation before chemotherapy is steadily increasing. Nevertheless, the number of patients who can really benefit from complex ART techniques such as ovarian tissue or oocyte/embryo cryopreservation remains very low mainly because of a too short time-interval between the cancer diagnosis and its treatment. Lack of adequate information regarding post treatment infertility risk and logistical difficulties to access to a highly specialized cryopreservation centre are also reasons of importance. It is now well-established that these patients are at high risk of infertility even if they return to a normal ovarian function. Therefore, for patients who could not benefit from fertility preservation before cancer treatment, and who have recovered spontaneous menstrual cycle, one might raise the question of oocyte freezing once the cancer cured.     

Fertility preservation: nonsurgical and surgical options

Improved surveillance and treatment regimens have resulted in decreased mortality rates among cancer patients, allowing these women to focus on survival and quality of life, including the ability to preserve their fertility. The treatments that have improved survival among both adults and children diagnosed with cancer are often gonadotoxic, especially those that employ high doses of alkylating agents and radiation therapy directed near or toward the pelvis. The impact on the ovarian reserve is related to the accelerated depletion of the primordial germ cell pool resulting from these therapies. Nonsurgical approaches to fertility preservation, including embryo cryopreservation from in vitro fertilization, oocyte cryopreservation from controlled ovarian hyperstimulation, and in vitro maturation of oocytes, are discussed. Surgical approaches such as conservative gynecologic surgery, ovarian transposition, and ovarian tissue cryopreservation are reviewed. Guidelines from the American Society for Reproductive Medicine and the American Society of Clinical Oncology classify these treatments into established and experimental procedures, and they provide the practitioner with an optimal approach to preserve the fertility of these patients before the initiation of their cancer therapies.     

Cryopreservation of female reproductive potential

Storing female reproductive potential can offer enhanced prospects for future conception in women whose fertility is threatened by cytotoxic therapies. Human female reproductive potential can be cryopreserved and stored at very low temperatures as embryos or gametes. Gamete (oocyte) cryopreservation circumvents potential issues associated with ownership when future use is being considered and may, therefore, be more generally acceptable as an approach. Advances in the technology, in particular the clinical application of vitrification, have significantly improved the outcomes from mature oocyte cryopreservation, which are now comparable to those from embryo cryopreservation. In cases where mature oocyte cryopreservation is not feasible, ovarian cortex containing primordial follicles can be cryopreserved, and over 100 births have now been reported following grafting of stored ovarian tissue. Ovarian tissue cryopreservation is now an established approach to preserve future fertility for young women; however, the efficiency is difficult to determine particularly for the prepubertal tissue with a scarcity of data.     

Ovarian tissue cryopreservation: therapeutic prospects and ethical reflections

Along with improved survival, methods to preserve or restore the fertility potential of young women and children treated with cytotoxic chemotherapy or pelvic radiotherapy have been developed or are in the offing. Surgery, radiotherapy and chemotherapy can all impact on the future ovarian function, but patient and disease tailored application and use of preventive measures can limit ovarian damage. When the loss of reproductive ovarian function is unavoidable, different alternatives to preserve fertility or at least to restore the procreative potential are available. Creation of embryos by IVF, oocyte donation and cryopreservation of mature or immature oocytes are potential issues, the advantages and limitations of which are discussed. Recently, ovarian tissue cryopreservation has spurred interest in the medical literature as well as in the lay press as a method for preservation and restoring fertility. Considering the available data and current state of knowledge, we want to stress that this methodology is still in an experimental phase and we would like to caution against unwarranted enthusiasm of physicians and patients. The medical information preceding the informed consent should mention the actual uncertainties of this method. Moreover, the imperative character of the offer and in particular for paediatric oncological patients, the force of the moral rules that define parental obligations towards children should not be ignored.     

Vitrification of embryos and oocytes for fertility preservation in cancer patients

As survival rates and the life expectancy of those with malignancy have increased, more women in their reproductive years are referred for fertility preservation. Chemotherapy and radiotherapy can severely affect ovarian function, and the effect is irreversible. Therefore, it is optimal to attempt fertility preservation before chemotherapy and radiotherapy are initiated. Oocyte and embryo cryopreservation is the most common option for fertility preservation in women. Several reports have proven that embryo and oocyte cryopreservation can achieve a successful pregnancy. This review discusses the impact of chemotherapy and radiotherapy on ovarian function, and the importance of oocyte and embryo cryopreservation for fertility preservation. In addition, the current status of pregnancy outcomes and potential for cryopreserved oocytes to result in live births in cancer patients was reviewed. This may provide useful information for decision‐making in cancer patients regarding oocyte and embryo cryopreservation and fertility preservation.     

Is there any medical treatment to preserve fertility during chemotherapy in women?

Intensive use of radio-chemotherapy has greatly improved the prognosis associated with cancer in young girl or women patients. However, improvement of the vital prognosis is frequently associated with impairment of fertility and premature ovarian failure. In vitro fertilization (IVF) followed by embryo cryopreservation is an available method, which needs a partner and a pretreatment stimulation. Ovarian and oocyte cryopreservation are techniques showing great promise. However, the nec plus ultra would be to be able to protect ovaries during chemotherapy. Since more than 10 years Gonadotropin releasing hormone (GnRH) analogues have been investigated as possible means to preserve fertility in young women. However, even recent prospective, randomized studies do not demonstrate clearly their effectiveness. To prevent primordial follicle apoptosis, an inhibitor of tysosine kinase, imatinib, has recently been proposed and positively evaluated in mice. It could represent an interesting hope to preserve female fertility during chemotherapy.     

Ovarian cortex cryopreservation in pediatric and adolescent medicine

Background: Increased pediatric/adolescent cancer survivor rates have enhanced awareness of long-term effects of therapy, specifically gonadal failure. Ovarian cortex cryopreservation may hold the promise of fertility for those at risk for ovarian failure due to medical therapy. The object of this study was to determine if an ovarian cryopreservation program is feasible and to define suitable candidates.Method: A MEDLINE search supplemented by bibliographies. The review was limited to English articles on ovarian failure rates following radiation and/or chemotherapy and on ovarian cryopreservation. Investigators in the field were consulted to identify other sources.Results: Approximately one third of postpubertal females exposed to chemotherapy or radiotherapy develop ovarian failure. The risk is mostly significant for patients exposed to pelvic radiotherapy (up to 32% decrease in fertility) and alkylating agent based chemotherapy (infertility in 22%). A ninefold increase in premature ovarian failure results from exposure to combined pelvic radiotherapy and alkylator based chemotherapy. Practically all patients exposed to multiple agent chemotherapy combined with pelvic radiotherapy at doses used in preparation for bone marrow transplant will undergo irreversible loss of ovarian function. Currently human ovarian cortex can be cryopreserved, thawed and stimulated with gonadotrophins to produce follicles when transplanted into immunosuppressed mice, however there has yet to be any human pregnancies. The immunosupressed mouse model could also serve as a test to determine whether the tissue carries metastatic risk prior to reimplantation into the donor.Conclusion: Based on the literature we propose ovarian cortex cryopreservation and banking for postpubertal females prior to chemotherapy and/or radiation therapy that holds a high risk of ovarian failure. In the future this may provide oocytes for reproductive purposes. A protocol is currently under approval by the Hospital for Sick Children's ethics committee.