Best Practice & Research Clinical Obstetrics & Gynaecology
Volume 24, Issue 1 , Pages 101-112, February 2010

Cryopreservation of oocytes and embryos for fertility preservation for female cancer patients

  • Baris Ata, M.D (Clinical and Research Fellow)

      Affiliations

    • Tel.: +1 514 843 1650; fax: +1 514 843 1496.
    • ,
  • Ri-Cheng Chian, Ph.D (Assistant Professor)

      Affiliations

    • Tel.: +1 514 934 1934x3709; fax: +1 514 834 1496.
    • ,
  • Seang Lin Tan, MD, MBBS FRCOG FRCSC FACOG MMed(O&G), MBA

      Affiliations

    • Corresponding Author InformationCorresponding author. Tel.: +1 514 843 1658; Fax: +1 514 843 1678.
    • ,
  • James Edmund Dodds Professor and Chairman Obstetrics and Gynecology, Obstetrician and Gynecologist-in-Chief

McGill Reproductive Centre, Department of Obstetrics and Gynecology, Division of Reproductive Endocrinology and Infertility, McGill University, Royal Victoria Hospital, 687 Pine Avenue West, H3A 1A1, Montreal, Quebec, Canada

published online 07 December 2009.

Article Outline

In vitro fertilization and embryo cryopreservation is regarded as the only established method for fertility preservation in female cancer patients. However, a possible delay in treatment of the primary disease due to ovarian stimulation, exposure to supraphysiologic estrogen levels induced by ovarian stimulation, the requirement for a male partner or willingness to use donor sperm for embryo production, legal, ethical, religious issues related to cryopreservation of embryos raise concerns for patients and physicians. Recent improvements achieved with oocyte vitrification have increased the effectiveness of oocyte cryopreservation rendering it a viable option, especially for patients without a male partner. In vitro maturation avoids treatment delay or exposure to increased estradiol levels associated with ovarian stimulation for in vitro fertilization. In vitro maturation combined with embryo or oocyte vitrification provides previously unavailable options for some patients and improves the services provided by a fertility preservation program.

Keywords: Fertility preservation, cryopreservation, vitrification, slow freezing, oocyte, embryo, in vitro maturation, Cancer

 

Cancer is a major health problem, and malignant neoplasms constitute the second most common cause of death, second only to cardiac disease.1 It is estimated that in 2009 approximately 713,220 women in the United States will be diagnosed with cancer.2 Improved treatment methods have resulted in a steady increase in the survival rates over the last decades.2 Eventually the number of cancer survivors increase every year. Accordingly, a growing number of women are faced with the risk of infertility resulting from gonadotoxic oncologic treatment. Breast cancer remains the most common cancer in females, representing 27% of all female cancers. Between 2002 and 2006, 12.4% of all breast cancer cases were diagnosed in women younger than 45 years, who are in their reproductive period.3 Based on this distribution, it can be anticipated that approximately 25,000 reproductive aged women will become candidates for gonadotoxic therapy due to just one type of cancer in only one country in a single year. Moreover, with similar improvements in the treatment of childhood cancers, it is estimated that one in every 250 adults will be a childhood cancer survivor by the year 2010.4 Patients who are exposed to gonadotoxic agents for the treatment of non-oncologic diseases such as systemic lupus erythematosus, those who are undergoing surgery for endometriosis as well as women with genetic disorders such as Turner syndrome and fragile-X pre-mutation face similar risks, further contributing to the population of women who need fertility preservation procedures.5, 6, 7, 8

Given the improvement in survival rates with cancer treatment and developments in the field of reproductive medicine, fertility preservation for female cancer patients has become a very timely and topical issue. With an increased awareness of the options available for fertility preservation, a greater number of women are being offered and are utilizing these technologies.

Today, several methods are available for preserving the reproductive potential of these patients. When the threat to gonads is limited to direct radiotherapy, surgically positioning the ovaries out of the irradiation field is an effective method and can be combined with other methods if deemed necessary.9 However, in the case of systemic administration of gonadotoxic agents, the gametes at risk should be removed from the body and preserved in some form until they can be reimplanted or used for reproduction upon completion of treatment for the underlying disease. Besides gonadotoxicity, advancing age during treatment is another concern. Fertility declines with age, and in some cases, treatment of the underlying disease may require several years, meaning that the natural decline in fertility may become an issue even in the absence of direct gonadotoxicity.10, 11

Administration of gonadotropin releasing hormone analogues or inhibitors of apoptosis, cryopreservation of unfertilized oocytes following in-vitro fertilisation (IVF) or in-vitro maturation (IVM), cryopreservation of embryos following IVF or IVM and ovarian tissue cryopreservation are the current methods available for fertility preservation. At present, embryo cryopreservation following IVF is the only method endorsed by the American Society of Clinical Oncology (ASCO) and the American Society of Reproductive Medicine (ASRM), while the other methods are still considered experimental.12, 13 However, fertility preservation is a relatively new field in the practice of reproductive medicine and oncology, and it attracts much attention. We are certain that opinions will change shortly in light of rapidly accumulating data from across the world. The method of choice for any particular patient depends on several factors including age, cancer type and stage, pending oncologic treatment, safety of ovarian stimulation, time available before gonadotoxic chemotherapy and the availability of partner sperm or the willingness of single patients to use donor sperm.

In this article, we will review the currently available literature on the cryopreservation of unfertilized oocytes and embryos.

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Cryopreservation of cells – controlled slow-freezing versus vitrification 

The term cryopreservation refers to the storage of viable cells at low temperature (normally at −196°C). However, neither human oocytes nor embryos are exposed to such a low temperature under natural conditions. They are prone to damage and subsequent loss of viability and function during cooling to such low temperatures. The three major mechanisms of damage are chilling injury that occurs between +15°C and −5°C, ice crystal formation between −5 and −80°C, and fracture damage; i.e. the mechanical effect of solidified fluid within the cell that occurs between −50 and −150°C. Once the cell reaches −196°C, storage at this temperature is the least harmful period of the cryopreservation process. During warming, the cell is subject to the same injuries in reverse order.14 The occurrence of these events can be prevented to some extent by altering the rate of change in temperature and/or the amount of water in the cell. The size of the sample to be cryopreserved, its surface-to-volume ratio and water content are critical factors determining cryosurvival.

Among the many methods used for cryopreservation of biological samples, the two basic techniques employed in assisted reproduction laboratories are controlled slow-freezing (SF) and, more recently, an ultrarapid cooling method also known as vitrification. Both involve the use of cryoprotectants to minimize ice-crystal formation by drawing water from the cytoplasm through the osmotic effect (non-permeable cryoprotectants); or by preventing ice nucleation and growth either inside the cytoplasm (permeable cryoprotectants) or in the extracellular medium surrounding the cell (extracellular cryoprotectants). Unfortunately, the cryoprotectants currently in use have the potential to harm the cell, either through direct toxicity (permeable cryoprotectants) or through osmotic damage (non-permeable cryoprotectants). Cryoprotectant toxicity is proportional to its concentration and the duration of exposure.14

SF is chronologically the earlier technology, and involves cooling the cell at a strictly controlled slow rate that allows water to leave the cell after treatment with relatively low concentrations of cryoprotectants. Eventually, cytoplasmic viscosity is extremely increased without ice formation; i.e., vitrified. SF requires programmable freezing machines, and each round of cooling and thawing takes several hours.

On the other hand, vitrification involves ultrarapid cooling of the sample; i.e., transition from ambient temperature to −196°C in less than a second. In contrast to SF, the cooling rate is above 10,000°C/minute. This is achieved by loading the sample onto a carrier and submerging it following treatment with vitrification solution into liquid nitrogen (LN). While rapid cooling prevents chilling injury, this technique requires the use of very high concentrations of cryoprotectants to prevent ice-crystal formation, thus increasing the risk of toxicity. This is counteracted, however, by working with minute amounts. Expensive programmable equipment is not required for the vitrification of human oocytes and embryos. The technique requires minimum set up time but more hands-on time per oocyte/embryo.

One important difference between the two techniques is that while the sample is maintained in a closed container and never comes into direct contact with LN during SF, the solution covering the sample directly contacts LN during vitrification. This has raised concerns about possible disease transmission between open tools used for vitrification. Although the possibility of transmission of viral particles from LN to embryos has been documented under experimental conditions, no actual contamination of cryopreserved oocytes or embryos has ever been reported at the time of writing.15 However, research is ongoing to develop a closed vitrification system that does not significantly slow heat transfer and decrease the effectiveness of the vitrification process.

Relative merits of the two techniques with regard to oocyte and embryo cryopreservation will be discussed below.

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Embryo cryopreservation 

The successful cryopreservation of surplus embryos after IVF and resultant pregnancy following frozen-thawed embryo transfer (FET) was first reported in 1983, and the first child after embryo freezing was born in 1984.16, 17 For more than two decades, embryo cryopreservation (EC) has played an important role in assisted reproduction treatment (ART), providing couples with more than one attempt at embryo transfer after a single ovarian stimulation cycle with IVF, thus improving cumulative pregnancy rates while decreasing exposure to gonadotropins and reducing treatment costs. It is estimated that almost one quarter of the children born after ART are born following cryopreservation of mostly cleavage-stage embryos and, less commonly, blastocysts and oocytes.18 Most recent data from the Society for Assisted Reproductive Technology and the European IVF Monitoring Program report a pregnancy rate of 34% following FET in women younger than 35 years and an overall pregnancy rate of 19%, respectively.19, 20 Slow-freezing has been the most widely applied technique for the cryopreservation of embryos, while vitrification has been used more frequently recently. A recent review assessing the medical outcome of ART children born after cryopreservation reported reassuring results.21 The rate of preterm birth, birth defects and chromosomal abnormalities was not significantly different between children born after transfer of fresh or cryopreserved embryos. Similarly, these children demonstrated similar growth and mental development.21

Although the cryopreservation of embryos following a stimulated IVF cycle is considered the only established method of fertility preservation for female cancer patients, several points raise concern about this option. These are: (1) a possible delay of two to five weeks in treatment of the primary disease due to ovarian stimulation depending on the timing of the first consultation with the reproductive endocrinologist in relation to onset of the next menstrual cycle (2) exposure to supraphysiologic estrogen levels induced by ovarian stimulation (3) the requirement for a male partner or willingness to use donor sperm for embryo production (4) legal, ethical, religious issues related to cryopreservation of embryos in general. The method of choice for the cryopreservation of embryos is another relevant issue and these are addressed below.

Does IVF – embryo cryopreservation delay treatment of primary disease? 

A retrospective study addressing the above question concluded that having a reproductive medicine consult and subsequent ovarian stimulation followed by oocyte collection did not significantly delay the start of adjuvant chemotherapy in young patients with breast cancer.22 However, the actual time required for completion of the fertility preservation procedure, which starts with the initial reproductive medicine consultation and technically ends with oocyte collection, depends on the conditions of any particular clinic.

Ovarian stimulation takes between 2 and 5 weeks, depending on the stimulation protocol employed and the timing of the following menstrual cycle of the patient. Studies assessing the effect of the length of time between surgery and the initiation of chemotherapy on the survival of women with breast cancer report no detrimental effect of a delay in treatment if chemotherapy is started within 12 weeks after surgery.23, 24, 25 However, it must be emphasized that the external validity of these studies is limited to their inclusion criteria, and the potential effect of any delay in oncologic treatment due to fertility preservation procedures must be evaluated on a case-by-case basis together with the treating oncology team. In order to minimize any preventable delay, it is prudent to inform patients about the effects of treatment on fertility and the options for fertility preservation as early as possible in the course of oncologic diagnosis and treatment procedures.

The effect of elevated estrogen levels on underlying disease 

The risk of breast cancer is consistently found to be associated with persistently elevated blood estrogen levels.26 Serum estradiol (E2) levels are increased during ovarian stimulation for IVF and can reach levels twenty times higher than those of a natural cycle.27 Although the effect of a temporary increase in serum E2 levels on the risk of recurrence of breast cancer is controversial, these facts cause concern among both physicians and patients. Such concerns should not be limited to women with estrogen receptor positive breast cancer, because recent findings also suggest the presence of an indirect mitogenic effect of estrogen on hormone receptor negative breast cancer.28 Moreover, increased E2 levels can be relevant for patients undergoing fertility preservation treatment due to other oncologic or non-oncologic diseases considered to be estrogen sensitive, such as desmoid tumours, systemic lupus erythematosus or severe endometriosis.

In order to minimize the rise in estradiol levels in breast cancer patients undergoing IVF, Oktay et al. developed an ovarian stimulation protocol involving the concomitant use of an aromatase inhibitor, letrozole, with gonadotropins.29 Briefly, letrozole was started at a dose of 5mg/day on the second day of the menstrual cycle and gonadotropins were initiated two days later. A gonadotropin releasing hormone antagonist was used to prevent premature ovulation, and human chorionic gonadotropin (HCG) was administered when at least two follicles reached 19mm in diameter. Letrozole was reinitiated on the day of oocyte collection in order to prevent a rebound increase in E2 level. The mean peak E2 level was 406pg/ml (range 58 to 1,166pg/ml) in 79 women with breast cancer undergoing ovarian stimulation for embryo or oocyte cryopreservation.29 An average of 10.3±7.75 oocytes were retrieved and 5.97±4.97 embryos/oocytes cryopreserved per patient. Compared to 136 women who opted against ovarian stimulation, the recurrence and relapse-free survival rates were similar after a median follow up of 23.4 months after definitive surgery. However, it is interesting to note that with the same centre 63.3% of breast cancer patients referred for REI consultation declined ovarian stimulation and IVF due to concerns about delay of chemotherapy, effect of ovarian stimulation on cancer or costs associated with treatment.29

Ethical and legal issues associated with embryo cryopreservation 

When embryos are cryopreserved in a fertility preservation program, the patient/couple should make an advance decision on the fate of these embryos in the event that they are not transferred for any reason including the patient's failure to survive cancer. It should be documented whether the remaining partner is entitled to use the embryos for his own reproductive end or whether they are to be donated to a third party, used for research or discarded. Considering these issues and making such decisions can be particularly difficult for a patient who has been recently diagnosed with a life-threatening disease and is facing a demanding treatment period. Therefore, patients should be given appropriate counselling using a multidisciplinary approach involving a psychologist and a legal advisor.

Slow freezing or vitrification for embryo cryopreservation 

Several trials have been conducted to answer this question in non-cancer patients. A recent systematic review of randomized trials comparing laboratory and clinical outcome with SF or vitrification conclude that pregnancy rates were not statistically significantly different between the two methods (odds ratio (OR): 1.66, 95% confidence interval (CI): 0.98 –2.79, in favour of vitrification).30 However, vitrification was associated with significantly higher post-thawing survival rates, both for cleavage-stage embryos (OR: 6.35, 95% CI: 1.14–35.26) and for blastocysts (OR: 4.09, 95% CI: 2.45–6.84). Moreover, post-thawing blastocyst development of embryos cryopreserved at the cleavage stage was significantly higher with vitrification than with slow freezing (OR: 1.56, 95% CI: 1.07–2.27).30 It should be noted that all of the three studies that reported clinical pregnancy rates included in this review reported higher absolute figures in the vitrification arms and, given the significantly better laboratory results together with the favourable trend observed in clinical outcome, we have the impression that lack of statistical significance is more likely to be a matter of sample size.31, 32, 33 Similar to IVF embryos, we achieved higher survival and pregnancy rates following vitrification of cleavage stage IVM embryos as compared with slow-freezing.34 In fact, vitrification is the only method of cryopreservation currently employed at the McGill Reproductive Centre. The method of choice should be determined by the ART center based on its own experience and figures.

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Oocyte cryopreservation 

In the context of fertility preservation for cancer patients, oocyte cryopreservation is recognized as an option for women without a partner and opting against using donor sperm.12, 13 It is considered an investigational procedure in the ASCO and ASRM reports as well as in a working-party report of the Royal Colleges of Physicians, Radiologists and Obstetricians and Gynaecologists on the management of cancer patients undergoing gonadotoxic treatment.35 The major motivation behind this opinion is that a relatively better clinical outcome being reported with EC than with oocyte cryopreservation.

However, these opinions by ASRM, ASCO and the Royal Colleges are based on data published prior to 2005, 2006 and 2007, respectively. A meta-analysis of the efficiency of oocyte cryopreservation published in 2006 reported live-birth rates of 1.9% and 2% per oocyte thawed after slow freezing and vitrification, respectively.36 The vast majority of data on oocyte cryopreservation were from experience with slow freezing at that time, and a substantial amount of relevant data regarding vitrification has subsequently been published.

Challenges of oocyte cryopreservation 

Successful cryopreservation of a mature human oocyte at the metaphase-II stage (MII) has been a challenge for biologists. Although the first ongoing pregnancy achieved with frozen-thawed human oocytes was reported more than two decades ago, the technique showed little, if any, improvement until recently.37 The size of the oocyte, which is the largest cell in the human body, together with its spherical shape, prevent the even distribution of cryoprotectants and heat changes in a timely manner, rendering the cell susceptible to damage during cooling and warming.38 The oocyte is particularly prone to chilling injury, resulting in irreversible damage to its membranes.39 The presence of the meiotic spindle with the chromosomes lined up along the equatorial plate is another concern. These microtubules are considered prone to damage, and spindle dysfunction has been suggested to increase the risk of chromosome misalignment and aneuploidy in the mouse.40 However, we and others have found the incidence of aneuploidy to be similar in vitrified/warmed and fresh in vivo matured or in vitro matured mouse oocytes.*41, 42 In the mouse model, we observed similar aneuploidy rates in oocytes following vitrification or slow freezing.43 Currently available data do not seem to suggest an increase in aneuploidy rate in humans following vitrification.44, 45, 46 Intuitively, smaller sized immature oocytes without the meiotic spindle can be anticipated to better survive cryopreservation; however, laboratory and clinical outcomes of cryopreservation of oocytes at the germinal vesicle (GV) stage by slow-freezing or vitrification has not been as good as those achieved with mature oocytes.47 Despite similar survival rates for GV and MII ocytes after vitrification, the maturation rate of vitrified warmed GV oocytes is significantly lower than that of fresh GV oocytes.47, *48

Recent results achieved with oocyte vitrification 

The major advantage of vitrification over slow-freezing in the context of oocyte cryopreservation seems to be minimization of chilling injury due to the accelerated cooling rate. Open systems used for rapid cooling are suggested to decrease the extent of fracture damage as compared with the closed systems used for slow-freezing.38 As expected, better results have been reported recently with vitrification.*43, 49, 50, 51, 52, 53, 54 In a clinical trial at the McGill Reproductive Center involving 38 infertile women, oocyte vitrification (OV) using the McGill Cryoleaf resulted in a mean survival rate of 81% post-thawing, a 76% fertilization rate, a clinical pregnancy rate per cycle of 45%, a live birth rate of 40%, and 22 healthy babies.55 In a comparative study of oocyte cryopreservation, Fadini et al. reported significantly higher survival, fertilization, implantation and pregnancy rates with vitrification compared with slow-freezing.56 Rienzi et al. compared embryo development of fresh and vitrified sibling MII oocytes in a randomized trial.57 The cryosurvival rate of vitrified oocytes was 96.8%; fertilization rates and the incidence of top-quality embryos were similar in two groups. Consequently, vitrification is becoming a widely applied technique for oocyte cryopreservation. In fact, large-scale oocyte donation programs have started to routinely bank oocytes rather than using fresh oocytes to avoid the inconvenience associated with synchronisation of donors and recipients. Encouraging results have been achieved with the use of vitrified/warmed oocytes in donation programs. Cobo et al. reported a 96.7% survival rate for vitrified warmed donor oocytes. Mean donor age was 26.7 years. When the resultant embryos were transferred to recipients with a mean age of 40.8 years, implantation and pregnancy rates were 40.8% and 65.2%, respectively.58

Obstetric outcome of oocyte vitrification 

In a review of 165 pregnancies and 200 infants conceived following oocyte vitrification, the birth weight and the incidence of congenital anomalies (2.5%) were comparable to those following spontaneous conception or IVF treatment.45 A more recent review of children born after oocyte cryopreservation identified 532 and 392 live-born children resulting from slow-frozen and vitrified oocytes, respectively.46 The incidence of congenital abnormalities in these children was 1.3%, similar to that of major structural and genetic birth defects observed in all live births in the United States as reported by the Center for Disease Control.59

Despite the absence of direct observation in cancer patients, as long as oocytes are collected before exposure to gonadotoxic therapy, similar results can be expected in women who wish to freeze their oocytes for fertility preservation. In our opinion, oocyte cryopreservation should now be considered an established rather than an experimental protocol.

Social and ethical case for oocyte cryopreservtaion 

Although infertility is regarded as a couples' issue, cancer is an individual's disease. Accordingly, fertility preservation should aim to preserve not only the individual's germ line, but also her autonomy for her own reproductive potential. In the case of embryo cryopreservation, the embryos are not anticipated to be transferred before at least three years for the vast majority of patients. Living with cancer, going through oncologic treatment or being a cancer survivor is not only a physical challenge but also a psychological one. Like anybody else, these women may experience changes in their civil status in one way or the other during this demanding and uncertain period. For single women, generating then freezing embryos conceived with donor sperm is obviously not the same as cryopreserving unfertilized oocytes for possible use with a future partner. On the other hand, a proportion of couples, unfortunately, separate in the face of cancer. In case of separation, the former male partner will have rights over the embryos, with all possible legal and ethical implications. The ex-male partners may disagree to using the embryos and to conceive a child, as in the case of Evans vs. Johnson.60 In general, if there is any doubt, it is better to freeze oocytes since oocytes belong to the woman, while embryos belong to the couple. We believe that in contrast to embryo cryopreservation, oocyte cryopreservation provides the most effective means of ensuring the reproductive autonomy of the patient.

Another advantage of oocyte cryopreservation is that it avoids the ethical and religious quandaries associated with the storage and disposal of embryos. Accordingly, each patient should be given the success rates for each available option based on the treating center's own figures in order to adequately and fairly inform her decision.

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The role of in-vitro maturation in fertility preservation 

IVM has become an effective treatment option for many infertile women, resulting in the birth of over 2000 healthy infants without any increase in fetal abnormalities or miscarriage rates in comparable patients.61, 62, 63, 64, *65, 66 Despite satisfactory pregnancy rates in appropriately selected patients, overall pregnancy rates remain lower than those of IVF cycles in general.67 However, an effective IVM program will avoid most of the above-mentioned problems and concerns associated with stimulated IVF cycles in cancer patients.

Immature oocyte retrieval in an unstimulated menstrual cycle or from ovarian tissue biopsies followed by IVM and oocyte or embryo cryopreservation provides a novel fertility preservation strategy.68, *69 Avoiding ovarian stimulation provides several important advantages for these special-needs patients. Compared to 2–5 weeks required for a stimulated IVF cycle, immature oocyte retrieval can be done within 2–10 days, depending on the patient's menstrual status.68 Moreover, immature oocytes can be collected even in the luteal phase. We reported three women without male partners seeking fertility preservation prior to chemotherapy who presented for the first time in the luteal phase of their menstrual cycle and were to undergo gonadotoxic treatment immediately. Five to seven immature oocytes were recovered by luteal-phase oocyte retrieval from these women. Three to five MII oocytes were vitrified following IVM. Two of the three women later underwent one and two more collections, respectively, in the follicular phase of the next cycle(s) and additional immature oocytes were vitrified following IVM.70 Moreover, immature oocyte collection in the luteal phase provides a rescue option for a patient who experiences a premature luteinizing hormone surge during ovarian stimulation.71 Although, cancelling the treatment cycle can be an option for the regular patient, cancer patients undergoing fertility preserving treatment usually don't have time for a new treatment cycle and require immediate solutions. We were able to collect 4 immature oocytes in a breast cancer patient who has had a premature LH surge during an ovarian stimulation cycle. Two GV oocytes were matured in vitro and fertilized successfully, resulting in vitrification of two embryos.71

In patients with hormone-sensitive tumours, even a temporary increase in estradiol levels is avoided in an IVM cycle, rendering it a good option. Avoiding ovarian stimulation eliminates the risk of ovarian hyperstimulation syndrome (OHSS), which is a potentially lethal iatrogenic complication.72 When superimposed on underlying cancer, OHSS can have serious consequences on the health of these patients and can cause further delay in pending oncologic treatment. Finally, there is no need for daily gonadotropin injections in an IVM cycle, and associated costs and inconvenience are avoided.

Immature oocytes can also be harvested from ovarian biopsy specimens and can be fertilized or vitrified following IVM.69 This combination of ovarian-tissue cryobanking and IVM represents a new strategy for fertility preservation.7 We retrieved 11 immature oocytes from a wedge resection specimen in a 16-year-old patient with mosaic Turner syndrome. Eight of these oocytes were vitrified following IVM. In four women with cancer, we harvested 11 immature and 8 mature oocytes from wedge biopsy specimens. Eight of the 11 immature oocytes reached MII stage following IVM and were vitrified.69 In a pilot study at the MRC on IVM-OV, a live birth rate of 20% per cycle was achieved, including the world's first four live births from vitrified IVM oocytes.*55, *73

In conclusion, IVM combined with embryo or oocyte vitrification provides previously unavailable options for some patients and improves the services provided by a fertility preservation program. To date, the McGill Reproductive Centre has provided fertility preservation to 180 patients with breast, hematological, brain, soft-tissue, colorectal and gynecological cancers, more than 100 of these women have oocytes or embryos cryopreserved following IVM (Tables 1 and 2). Primary-care physicians and oncologists need to be made aware of the available fertility preservation options in order to allow early discussion with their patients followed by referral, if desired, to an ART center that offers the full range of fertility preservation options. A suggested algorithm is presented in Fig. 1.

Table 1. Fertility preservation in cancer and autoimmune disease patients.
IVM/EVIVF/EVIVM/OVIVF/OV
Patients45207044
Mean age (± SD)32±5.129.9±5.028.2±6.327.8±6.1
GV retrieved (median, range)399 (6;0–27)44 (4;1–13)667 (7;1–39)114 (3;0–17)
Maturation % ± SEM63.1;±3.7865.74;±11.5567.38;±2.7357.89;±7.21
MII retrieved (median, range)82 (2;0–7)159 (10;4–20)117 (1;0–12)479 (7;0–32)
Fertilization rate % ± SEM79.9±2.670.79±4.59––
EF - median; range4;1–167;1–23––
OV - median; range––6;0-409;0–37

IVM, In vitro maturation; EV, embryo vitrification; IVF, In vitro fertilization; OV, oocyte vitrification; SD, standard deviation; SEM, Standard error of mean.

Table 2. Number of patients with different malignancies who underwent different fertility preservation procedures.
IVM/EVIVF/EVIVM/OVIVF/OV
Hematological malignancy7101515
Breast malignancy311363
Gynecological malignancy1247
Brain malignancy2355
Sarcoma1136
GIT Malignancy1113
Melanoma0001
Autoimmune diseases1143
Desmoid Tumour1121
Total45207044

IVM, In vitro maturation; EV, embryo vitrification; IVF, In vitro fertilization; OV, oocyte vitrification.

  • View full-size image.
  • Figure 1 

    Suggested algorithm for fertility preservation. Reproduced from Chian RC, Huang JY, Gilbert L et al. Obstetric outcomes following vitrification of in vitro and in vivo matured oocytes. Fertil Steril 2009;91:2391–8.

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Conflict of interest statement 

None of the authors have any conflict of interest associated with the content of this review.

Practice points

 


•In vitro fertilisation and embryo cryopreservation is the ‘tried and true’ effective method for fertility preservation in cancer patients. However, possible effects of a delay in treatment and elevated estrogen levels on the underlying disease must be assessed on a case-by-case basis in a multidisciplinary approach.

•Specific ovarian stimulation protocols, which aim to decrease the time required and minimize increase in endogenous estrogen levels, have been developed for cancer patients.

•Vitrification seems to be a more efficinet technique than slow-freezing for cryopreservation of embryos and oocytes.

•In vitro maturation expands the options for fertility preservation, it provides shorter time to oocyte collection, avoids a rise in estrogen levels associated with ovarian stimulation.

•It is possible to collect immature oocytes in the luteal phase and use them for fertility preservation following in vitro maturation.

•There is no single best fertility preservation method for all patients. The optimum method should be chosen based on the conditions on each individual patient. In fact, a combination of methods can be used; i.e. ovarian tissue freezing with simultaneous immature oocyte colelction or luteal phase immature oocyte collection followed by mature oocyte collection with ovarian stimulation in the subsequent menstrual cycle.

•In case of embryo cryopreservation, the male partner has certain rights over embryos generated for future use. In this case, fate of these embryos under different scenarios must be discussed in advance with the couple. Appropriate medical, psychological and legal counselling must be provided.

•Primary-care physicians and oncologists need to be made aware of the available fertility preservation options in order to prevent loss of valuable time and allow referral to an ART center that offers the full range of fertility preservation options.

Research agenda

 


•Better identification of the effect of a temporary increase in estrogen levels on estrogen sensitive tumors.

•Methods to further improve outcome of oocyte and embryo cryopreservation.

•Methods the increase the implantation rate of embryos generated with in vitro matured, vitrified oocytes.

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PII: S1521-6934(09)00145-X

doi:10.1016/j.bpobgyn.2009.11.007

Best Practice & Research Clinical Obstetrics & Gynaecology
Volume 24, Issue 1 , Pages 101-112, February 2010

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