2005 © Oxford University Press
Ovarian Tissue Preservation and Future Fertility: Emerging Technologies and Ethical Considerations
Affiliations of authors: Department of Obstetrics and Gynecology—Yale University Fertility Center, New Haven, CT (PP); Department of Obstetrics and Gynecology—Hospital University of Pennsylvania, Philadelphia, PA (SB); Center for Bioethics, University of Pennsylvania, Philadelphia, PA (AC)
Correspondence to: Pasquale Patrizio, MD, MBE, HCLD, Yale Fertility Center, 150 Sargent Drive, 2nd Floor, New Haven, CT 06511 (e-mail: pasquale.patrizio{at}yale.edu).
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ABSTRACT |
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 Top Abstract IntroductionOVARIAN TISSUE HARVESTINGIVM OF EARLY-STAGE OOCYTESETHICAL CONSIDERATIONS OF...ETHICAL CONSIDERATIONS FOR...CONCLUSIONSReferences |
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Both adult women and prepubertal girls facing cancer treatment may have the option to harvest and cryopreserve ovarian tissue. If they have successful therapy for their disease, the tissue may be autotransplanted back into the woman's body or follicles may be harvested and matured in vitro. These techniques all remain experimental, however, and should be performed only by specialized centers that can provide a multidisciplinary team. The procedures should be done under approval from an Institutional Review Board with proper assurance of informed consent. Although the costs for research could be assessed to patients if no research funds are available, clinical fees should not be charged at this stage in the development of these technologies. Consideration should be given to the protection of minors by ensuring parental informed consent and child assent whenever possible. Disposition of cryopreserved gonadal tissue in the event of the participant's death should be formally designated. A registry should be established to follow the health of participants and their eventual offspring.
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INTRODUCTION |
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TopAbstractIntroductionOVARIAN TISSUE HARVESTINGIVM OF EARLY-STAGE OOCYTESETHICAL CONSIDERATIONS OF...ETHICAL CONSIDERATIONS FOR...CONCLUSIONSReferences |
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It is estimated that nearly 25% of cancers—the most common being breast cancer—affect women who have not had a child or who have delayed childbearing (1). The contemporary use of powerful chemotherapeutic and radiotherapy protocols means that a cure for many cancer patients can be realized. In pediatric cancers, for instance, the 5-year survival for all diagnoses is 77%; for women under 45 with breast cancer (all stages), the 5-year survival is 83% (2). As a result of this progress, a broader therapeutic focus has emerged for cancer patients and their health care providers, one that considers both optimizing survival probability and ensuring quality of life (3,4). Included in this quality of life paradigm is a consideration of fertility impairment that may result from the therapies used to treat these illnesses. Reproductive-aged women may also require medical or surgical therapies for benign conditions that pose a threat to their reproductive capacity. Treatment of autoimmune conditions such as systemic lupus erythematosis with alkylating chemotherapeutic agents can induce diffuse follicular atresia and predispose to premature ovarian failure. Surgical treatment of benign gynecologic conditions such as recurrent ovarian cysts or severe endometriosis may require bilateral oophorectomy, resulting in surgical menopause and sterility.
Since the success of egg freezing is still suboptimal, the only established option for females who wish to preserve their fertility is embryo cryopreservation after in vitro fertilization (IVF) (4,5). However, women who could take advantage of IVF may not have a partner when faced with this decision and may not be willing to use donor sperm. Moreover, patients with cancer may face serious morbidity if therapies are withheld for the period of time required to complete a cycle of IVF, making the evolution of more rapid fertility-preserving technologies critical (4–6). Finally, physiologic and social barriers make this option untenable for prepubertal girls.
Novel strategies for fertility preservation in young women and in girls that may circumvent some of these challenges are currently being investigated. Prior to their implementation, however, they must be deemed safe and effective and should be subjected to rigorous ethical deliberation. This overview will address ethical issues surrounding the emerging technologies of ovarian tissue harvesting, cryopreservation, and autotransplantation as well as the isolation and in vitro maturation (IVM) of early-stage oocytes.
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OVARIAN TISSUE HARVESTING |
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TopAbstractIntroductionOVARIAN TISSUE HARVESTINGIVM OF EARLY-STAGE OOCYTESETHICAL CONSIDERATIONS OF...ETHICAL CONSIDERATIONS FOR...CONCLUSIONSReferences |
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The isolation and cryopreservation of ovarian cortical strips followed by future autologous transplantation represents a promising intervention for fertility preservation currently being investigated. These cortical strips are rich in primordial follicles and can be isolated laparoscopically either by ovarian biopsy or oophorectomy, if necessary (4,5,7).
Most of the current knowledge concerning ovarian tissue cryopreservation and transplantation has been derived from animal models, though in recent years human data have started to emerge. Gosden et al. (8) achieved success in short-term xenografting (experiments carried out up to 18 days) of previously cryopreserved human ovarian tissue into immune-deficient mice. Survival of primordial follicles ranged from 44%–84%. Follow-up studies demonstrated survival of primordial follicles from xenografts of human tissue to immune-deficient mice for longer periods of time. After 22 weeks, grafts demonstrating folliculogenesis and numerous surviving primordial follicles were recovered from the mice, indicating that the freezing technique utilized was capable of preserving the developmental competence of the primordial follicles (8). Overall, cryopreservation of human ovarian tissue allows for recovery of the majority of primordial follicles, with major losses occurring at the time of revascularization and/or reperfusion (9).
Experience with transplantation of human autologous ovarian cortical strips is still in its earliest stages. Several investigators have performed procedures isolating cortical strips followed by transplantation of fresh or frozen-thawed grafts in orthotopic (pelvis) or heterotopic (i.e., subserosal or subcutaneous) locations in a small series of patients (7,10,11). Oktay et al. have achieved success with fresh and frozen-thawed autologous transplants placed orthotopically and heterotopically with respect to folliculogenesis (spontaneous and induced) and ovulation (12,13). Moreover, this group of investigators recently reported the development of a four-cell embryo after intracytoplasmic sperm injection (ICSI) in a patient with a frozen-thawed autologous heterotopic ovarian graft (10). The most notable achievement of this technology occurred with the birth of the first human conceived after orthotopic transplantation of cryopreserved ovarian tissue in September 2004. Ovarian cortical biopsies were isolated from a patient with stage IV Hodgkin lymphoma and cryopreserved prior to the initiation of chemotherapy. Six years after the initial diagnosis, biopsies were thawed and transplanted back to the patient orthotopically (close to the hilus of the right ovary). Resumption of spontaneous ovulation was confirmed 5 months post-transplant, followed 6 months thereafter by the conception of a spontaneous single intrauterine pregnancy. These achievements support the feasibility of this technology to achieve pregnancies in humans in the future (14).
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IVM OF EARLY-STAGE OOCYTES |
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TopAbstractIntroductionOVARIAN TISSUE HARVESTINGIVM OF EARLY-STAGE OOCYTESETHICAL CONSIDERATIONS OF...ETHICAL CONSIDERATIONS FOR...CONCLUSIONSReferences |
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An alternative to the autotransplantation of frozen-thawed ovarian cortical strips is the isolation of early-stage oocytes followed by IVM and IVF or ICSI. These oocytes could be isolated from cortical ovarian biopsies after thawing. Primordial oocytes have shown better survival after cryopreservation than mature oocytes because of their small cell size, lack of zonae pellucida, and lack of spindle apparatus (4–6,9). Furthermore, due to their relative abundance in the ovary, they are an ideal target for in vitro follicular maturation after cryopreservation and thawing.
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ETHICAL CONSIDERATIONS OF FERTILITY PRESERVATION |
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TopAbstractIntroductionOVARIAN TISSUE HARVESTINGIVM OF EARLY-STAGE OOCYTESETHICAL CONSIDERATIONS OF...ETHICAL CONSIDERATIONS FOR...CONCLUSIONSReferences |
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The key reason for pursuing fertility preservation by the methods described previously is to restore personal autonomy to those who are unable to conceive. Fertility preservation also provides a way for individuals who have lost their capacity for fertility as children or young adults to exercise that choice later in life. These are not trivial values. Reproduction is a very important capacity for many, and its loss can be devastating. The possibility that some women might postpone cancer treatment in the pursuit of lengthy strategies to preserve fertility underscores this dilemma and compels the emergence of rapid methods of fertility preservation.
However, the practice of fertility preservation raises a number of ethical concerns. Most important, ovarian tissue cryopreservation, autotransplantation, and in vitro follicular maturation should be considered experimental procedures because of the uncertainties and risks associated with these technologies (7,15,16). Technically speaking, it is still unknown whether it is better to store the ovarian tissue by slices, by cutting the ovary in half, or by freezing the ovary in its entirety. Data concerning the maximum lifespan of ovarian cortical grafts—either fresh or frozen-thawed—is also limited. Such information is crucial to inform practitioners' decisions about the optimal timing of transplantation. Follow-up of subjects to date has not demonstrated graft survival beyond 3 years (17). Important determinants of graft survival include the degree of follicular injury sustained during the initial ischemia and during the processes of cryopreservation and reperfusion. Since the lifespan of grafts is limited, it is possible that transplantation will have to be performed at the point that conception is desired and that more than one graft will be needed to conceive (4,17).
A potential risk of the autotransplantation of ovarian cortical strips—especially in patients with hematological cancers—is the possibility of reintroducing malignant cells stored in the tissue to a patient who has been cured (3,4,18–20). While it is difficult to fully quantify this risk in humans, animal data exist that suggest this is a potential concern. Using a mouse model, the transmission of lymphoma from diseased to healthy mice through allografts of frozen-thawed ovarian tissue has been demonstrated (21). In humans, it seems that lymphomas do not spread to the ovary while leukemias do. The possibility of cancer reintroduction through ovarian tissue grafts highlights the necessity of devising reliable strategies to screen gonadal tissue prior to cryopreservation and transplantation (18). The potential need to purge tumor cells from ovarian grafts has recently been addressed by a group of investigators who devised an in vitro model aimed at the eradication of tumors cells while preserving ovarian follicles (20).
An advantage of IVM of oocytes is the avoidance of the risk of reintroducing tumor cells as with autologous tissue grafts. This approach, however, is limited by the difficulty of maturing very-early-stage follicles (primordial and primary) to the antral stage (4,22). Although successful IVM of primordial follicles to both preantral and preovulatory stages has been demonstrated in mice, human studies have not been able to replicate this outcome (23,24). Investigators have been able to mature human preantral follicles to the antral stage in vitro using follicle-stimulating hormone stimulation, though with considerable loss of oocytes (25–27).
In light of these considerations, in vitro oocyte maturation and ovarian cortical strip cryopreservation should be offered only under conditions assuring appropriate research conduct. This includes obtaining institutional review board approval and using an informed consent procedure that accurately and explicitly outlines procedural risks and benefits. Special consideration must be given to including pediatric patients and the disposition or custody of gametes, reproductive materials, and organs. In the absence of funds from federal or private granting agencies, reasonable clinical fees may be charged to cover reimbursement expenses. However, the procedure should not be advertised as a routine clinical service.
At present, there is little consensus in the field about how best to design clinical trials for fertility preservation. Given the innovative nature of the proposed practices, how can informed consent and respect for the autonomy of the patient best be achieved? Who should be selected for initial research protocols, and on what basis? Can the moral principle of beneficence be upheld if research on the cryopreservation of ovarian tissues poses significant risk to any children who might result from this technique? How will guidelines for the storage of reproductive tissue be determined and by whom? How is access to the procedure to be determined—will there be any restrictions on who can use this technique based on health factors, age, or other social considerations? Will follow-up of infants conceived from these procedures and of their mothers be mandated?
Research subjects should be mentally competent and fully able to understand the risks, alternatives, and uncertainties that surround ovarian transplantation (children represent an exception to this recommendation). While the benefits of gamete cryopreservation are very promising, they are largely unquantifiable because human data concerning the survival of follicles after the freeze-thaw-transplant process are limited. Moreover, patients should not be provided false hope about the probability of fertility preservation. Alternatives to ovarian cryopreservation should be offered, and patients should be given the option of no intervention (28).
The risks of the procedures should be discussed with patients at a level they can comprehend, and their understanding of the risk information should be carefully assessed. Long-term risks must also be discussed. For example, children who result from these forms of fertility preservation might have an elevated lifetime risk of cancer related to a genetic cancer predisposition (18). The risk of reintroducing malignant cells to the patient after autotransplant of ovarian tissue should also be mentioned. These risks may be theoretical and remote, but failure to disclose them to potential patients would violate the essence of informed consent.
Ideally, the decision about who is a candidate for fertility preservation procedures should be made by a team of providers including a medical oncologist, a reproductive endocrinologist, a psychologist, and a pathologist all guided by written protocols which can be shared with patients. No center should be involved in testing this procedure without making clear its qualifications for undertaking the experiments, what standards of procurement and storage will be followed, and how it will follow up to determine the safety of this procedure both for women and for any resulting offspring they may have (29). At least initially, the principle of protecting the interests of children who might be created by this technique might lead centers to restrict the age at which women could seek to utilize transplanted ovarian tissue, how long such tissue could be preserved before use, and what sorts of medical criteria women who seek to use their tissue might be required to meet prior to retransplantation. It may also be important to restrict custody and transfer of stored ovarian tissues to the women from which they are obtained in order to avoid problems of nonallogeneic transplantation. Finally, it would be advisable to establish a mandatory registry for data collection on outcomes of the patients who undergo the procedures and the children conceived through them for safety monitoring purposes (28).
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ETHICAL CONSIDERATIONS FOR FERTILITY PRESERVATION IN CHILDREN |
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TopAbstractIntroductionOVARIAN TISSUE HARVESTINGIVM OF EARLY-STAGE OOCYTESETHICAL CONSIDERATIONS OF...ETHICAL CONSIDERATIONS FOR...CONCLUSIONSReferences |
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While the desire to preserve fertility in children is morally commendable, it raises additional ethical concerns. Children represent a unique and vulnerable population with respect to medical research. They have diminished autonomy, have a diminished capacity to understand the risks and benefits of research objectives, and lack the ability to provide consent for research studies. As a result, they require special protection (28,30). Until very recently, institutional attitudes impeded significant participation by children in medical research for fear of exploitation (30).
The immediate risks associated with harvesting ovarian tissue from a child are slightly greater than minimal. However, in the context of illness, this might be tolerable, especially if the procedure to procure the tissue is combined with a therapeutic procedure that requires anesthesia (28).
With respect to childhood fertility preservation, proper attainment of informed consent from a legally authorized representative (i.e., parental or guardian) and assent by the child, when possible, must be ensured (30,31). While parents may be competent to consent for their children, the scenario is very complex both clinically and emotionally. Support and counseling from persons not affiliated with or employed directly by the research program must be available to families considering participation in this type of research.
In order to overcome some of the practical obstacles involved in the consent process, it can be performed in stages (32). If a two-stage process were adopted, the issues of gonadal harvesting and storage and gamete manipulation could be handled as two separate subjects at two distinct time points. The decision to harvest gametes would be made at the time of cancer diagnosis, and consent for the procedure would be left to parents or guardians. The decision of how to use the gametes could be made at a future point (second stage) by the patient in adulthood. At such a point in time, the patient would be better able to express personal preferences about the handling of the tissue based on an enhanced capacity to understand the nature and ramifications of the interventions proposed (33).
Such a two-step process would also address the dilemma of posthumous reproduction. The law is unclear on who has rights to utilize the gametes if the donor dies. If it is determined at the outset that parental consent is sufficient for only the procurement and cryopreservation of gametes and that the ultimate fate of the tissue lies with the donor, then the tissue could not be used by any other person if the childhood donor does not survive to adulthood. Such conditions would prevent the use of gametes for a purpose that the donor could not have envisioned and was not able to conceptualize when originally banking the tissue. It is important to clarify these dispositional issues at the time of procurement (33).
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CONCLUSIONS |
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TopAbstractIntroductionOVARIAN TISSUE HARVESTINGIVM OF EARLY-STAGE OOCYTESETHICAL CONSIDERATIONS OF...ETHICAL CONSIDERATIONS FOR...CONCLUSIONSReferences |
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In summary, fertility preservation utilizing gonadal tissue cryopreservation is a promising though experimental approach for children or young women facing cancer. The following points summarize our recommendations to ensure the best ethical principles: 1) Ovarian tissue cryopreservation should be considered an experimental procedure; 2) it is reasonable, in the absence of grant funds, to seek reimbursement from patients to cover the expenses of the research but not to charge clinical fees for this service and not to advertise the procedure as a routine clinical service; 3) tissue cryopreservation should be performed only in a few specialized medical centers able to offer a consulting team of experts; 4) a proper an institutional review board–approved consent should be in place and should explain both the known and the theoretical risks of the procedure; 5) a registry should be established and maintained to collect accurate follow-up information on outcome and on offspring born; and 6) for children, a two-stage consent process should be implemented.
As additional data from research on early-stage gamete isolation and cryopreservation becomes available, clinical practice should evolve to accommodate future ethical questions and concerns. Even if cryopreservation turns out to be scientifically practical, it will require close attention to the ethical and social questions it raises in order to evolve into a key component of care for the infertile.
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