Fertility Preservation

Reproductive Dysfunction as a Result of Nononcologic Conditions or Their Treatment

Although the primary indication for fertility preservation is to avoid the iatrogenic effect of cancer treatments (chemotherapy, radiotherapy, surgery) on fertility, there is a growing list of nononcologic conditions where fertility preservation should be considered due to the underlying condition or the effect of specific treatment regimens ( Table 37.1 ).

Reproductive Aging

Although there is a body of controversial literature suggesting that the ovary contains oogonial stem cells, their presence and functional relevance are still unclear; the widely accepted view is that females are endowed with a finite number of follicles making up the ovarian reserve. Females are born with approximately one million primordial follicles and this number drops throughout the reproductive lifespan, with follicular depletion accelerating in the mid to late 30s. Ovarian activity eventually ceases at menopause, when there are only approximately 1000 follicles remaining in the ovary. In addition to the age-dependent decline in egg quality, reproductive aging is also associated with a decline in gamete quality, with a progressive increase in oocyte aneuploidy as a major contributing factor. In particular, chromosome segregation errors related to meiotic nondisjunction and premature separation of sister chromatids contribute to age-related infertility, miscarriage, and an increased risk of having a child with birth defects. A large study of preimplantation genetic testing of embryos created by in vitro fertilization (IVF) demonstrated the lowest rates of aneuploidy (20%–27%) for women between 26 and 30 years of age and a steady age-related increase, with an 85% aneuploidy rate by 43 years of age. While these data suggest that the optimal time for women to attempt pregnancy is before their mid-30s, more women are delaying pregnancy beyond this age and seeking assisted reproduction for the treatment of infertility. Oocyte cryopreservation has been proposed as a method to expand the reproductive potential of aging women and has become a common indication for fertility preservation worldwide. Beyond fertility, reproductive aging has general health consequences because the loss of follicles results in decreased estrogen, which can negatively impact downstream tissue function (e.g., heart, brain, immune, bone, and uterus). Thus, ovarian tissue cryopreservation and transplantation for hormone replacement have been proposed as treatments to delay ovarian aging and prevent the sequelae of menopause. ^,

Conditions Associated With Premature Ovarian Insufficiency (POI)

Several genetic conditions associated with accelerated ovarian aging can also impact fertility. For example, females with Turner syndrome—who have either partial or complete absence of one X chromosome—are at risk of premature ovarian insufficiency (POI). In mosaic Turner syndrome, an X chromosome is lost during embryonic development, such that some proportion of the body’s cells contains two normal X chromosomes. Spontaneous puberty and normal gonadotropin and estrogen levels were found to be predictive of the presence of mature follicles in girls with Turner mosaicism, and several case reports have described fertility preservation efforts in this population. Cases of pregnancy have been reported in women with mosaic Turner syndrome, and recent work suggests that women with mosaic Turner syndrome may be candidates for fertility preservation by either tissue cryopreservation (in prepubertal girls) or hormone stimulation followed by oocyte cryopreservation (in postpubertal girls and women). ^, Men with Klinefelter syndrome (XXY) have normal testes development up to puberty but then develop hypergonadotropic hypogonadism with degeneration of the seminiferous tubules and almost total loss of sperm production. Small areas of the tubules may still produce viable sperm that are recoverable by surgical extraction procedures.

Females with BRCA mutations that confer an increased risk for ovarian cancer may undergo prophylactic oophorectomy and opt for fertility preservation at that time. In addition, there are a growing number of genetic mutations that have been associated with POI in animal and human studies. Early diagnosis of such mutations in the future may provide opportunities for fertility preservation in these populations. Patients with known genetic conditions should be counseled regarding the risk of passing the condition on to their children. Preimplantation genetic testing of embryos, prenatal diagnosis, and alternative methods for family building should be discussed.

Conditions Requiring Medical Treatment That Poses Reproductive Risks

Gonadotoxic treatment is not limited to cancer. Rheumatologic and autoimmune diseases, such as systemic lupus erythematosus, are treated with highly gonadotoxic agents. Furthermore, hematologic disorders such as thalassemia major, sickle cell anemia, aplastic anemia, Fanconi anemia, and myeloproliferative diseases do not inherently compromise reproductive function but are treated with hematopoietic stem cell transplant and newer gene therapies that place patients’ future fertility at risk. These treatments often require exposure to alkylating chemotherapy and radiation, which can significantly deplete the primordial follicles in the ovarian reserve and reduce the patient’s reproductive lifespan.

Conditions Requiring Surgical Treatment That Poses Reproductive Risks

Surgical complications may also threaten fertility due to disruption of tissue, formation of adhesions, and parenchymal damage. In boys, cryptorchidism, even after orchiopexy, can significantly decrease fertility later in life. Testicular tissue biopsy cryopreservation has been performed in boys with cryptorchidism, with spermatogonial survival and normal hormone production achieved after thawing. In males, genitourinary trauma is a serious nononcological condition that can threaten fertility. In fact, in 2016, the Secretary of Defense outlined a series of reforms to ensure fertility preservation was extended to wounded service members.

Transgender and Disorders of Sex Development (DSD)

Gender and sex diverse individuals, including transgender individuals and those with DSD, may be at risk of infertility, the reasons for which differ depending on the population. For example, transgender individuals possess inherent normal reproductive function, but infertility may occur due as a result of medical interventions required to facilitate phenotypic transition to the affirmed gender. On the other hand, infertility in individuals with DSD may be due to abnormal gonadal development, altered endocrine function, or premature gonadal failure. Working groups for individuals with gender and sex diversity have assembled to develop unified fertility preservation protocols for these populations. Fertility preservation counseling is advisable, and fertility preservation strategies may be appropriate in these populations.

Reproductive Dysfunction as a Result of Oncologic Conditions or Their Treatment

Survival rates for childhood cancer have steadily increased, with an overall cure rate above 80%. Approximately 1 in 530 young adults in the United States is a survivor of pediatric cancer. Maintenance of fertility is a very important quality of life issue for these individuals; however, an unfortunate consequence of life-saving cancer treatments is that nearly all aspects of both the male and female reproductive axis can be compromised. In the female, the hypothalamic-pituitary-gonadal (HPG) axis, the ovaries and ovarian follicles, and the uterus are directly affected by cancer treatments; in the male, the testes are at risk; specifically the germinal epithelium and Leydig cells ( Figs 37.1, 37.2 ).

Cancer, Cancer Treatment, and Female Reproductive Function

A fertile woman must have: (1) a functioning neuroendocrine system that regulates the menstrual cycle and can maintain a pregnancy; (2) a healthy pool of follicles that will grow in response to hormonal cues and produce mature and fertilizable gametes; and (3) a receptive uterus that will support embryo implantation and fetal development to term. It is unclear whether cancer itself affects female reproductive function. In one recent study, the success of ovarian stimulation was compared in women with malignancies prior to cancer treatment to a similar group of women seeking assisted reproduction for male-factor infertility. No differences were found between these two groups of patients in terms of the number of dominant follicles and retrieved oocytes, proportion of mature eggs, or fertilization rates. However, a small meta-analysis that examined all types of malignancies found that there were fewer numbers of oocytes retrieved from women with breast and hormone-dependent cancers.

Cancer treatment can affect all aspects of the female reproductive axis ( Fig. 37.1 ). For example, radiotherapy can damage growing follicles, which triggers either repair or elimination pathways. In general, actively dividing cells are more susceptible to radiation-induced death, and because oocytes in the young adult are arrested in prophase of meiosis I, they are more resistant to radiation than cells in mitosis. Primordial follicles, which are quiescent, also appear to be more resistant to radiation compared with growing follicles. Nevertheless, the human oocyte is sensitive to radiation therapy. The LD50, or the radiation dose required to destroy 50% of immature human oocytes, is less than 2 Gy. Mathematical modeling predicts that the effective sterilizing dose of radiation is inversely correlated with age: it is 20.3 Gy at birth and 16.5 Gy at 20 years of age.

The female neuroendocrine axis (HPG axis) is also vulnerable to cancer therapies. The HPG axis controls the menstrual cycle and pregnancy by regulating the secretion of hormones, including gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol, progesterone, and prolactin. Radiation therapy, particularly targeting the cranium, can cause altered hypothalamic and pituitary function. ^{, ,} The risk of gonadotropin deficiencies is directly related to the radiation dose to the hypothalamic-pituitary axis (HPA), with doses of 3000 to 4000 cGy placing the patient at risk. LH and FSH deficiencies are associated with oligomenorrhea or amenorrhea, ovulatory impairments, failed implantation, and early pregnancy loss.

The uterus functions primarily to support embryo implantation as well as fetal growth and development. Radiation can have negative long-term consequences on the ability of the uterus to support a future pregnancy. ^, Radiotherapy can reduce uterine volume and elasticity, damage the uterine musculature and endometrium, and decrease the vasculature. If women are able to conceive following radiotherapy, they may have an increased risk of adverse pregnancy outcomes, including miscarriage, placental abnormalities, preterm birth, and delivery of infants with low birth weights. ^, There is no exact dose of radiation to the uterus above which sustaining pregnancy is unlikely, though doses in the range of 1400 to 3000 cGy will cause uterine damage. Guidelines suggest that patients receiving more than 2500 cGy to the uterus in childhood be counseled to avoid attempting pregnancy.

In addition to being radiosensitive, the ovary is chemosensitive. Certain agents, particularly alkylators, can cause significant damage to the oocyte itself and to the somatic cells of dormant and growing primordial follicles, decreasing the ovarian reserve. Some females experience total destruction of the primordial follicle pool with treatment, resulting in acute ovarian failure, while others resume some normal function posttreatment but have a diminished primordial pool and ultimately POI. ^, Alkylating agents, especially cyclophosphamide and busulfan, are more gonadotoxic compared to other chemotherapeutic agents, including platinum-based drugs, plant alkaloids, and antimetabolites ( Table 37.2 ). Alkylating agents, which cause DNA breaks irrespective of cell cycle stage, are associated with a high risk of primordial follicle death and compromised stromal cell function. Age at exposure, chemotherapy agent used, and cumulative dose are important factors when considering a patient’s risk for ovarian dysfunction. It is well documented that age is protective and younger females can tolerate larger cumulative exposures with less impact on the primordial follicle pool than a woman who is closer in age to natural menopause.

Exposure to radiation and certain chemotherapies can accelerate the depletion of the oocyte pool. This depletion can cause acute ovarian failure or POI in some females. Follicle destruction, whether by radiation- or chemotherapy-induced mechanisms, not only leads to gamete loss but also results in impaired ovarian hormone production and uterine dysfunction. Although follicles may resist combined cancer therapies, the ovarian reserve may be compromised and depleted early, resulting in premature menopause. Moreover, both the negative effects of radiation and chemotherapy on estrogen-producing growing follicles can severely impair the menstrual cycle. It is also becoming clear that both the germ cells and the somatic components of the ovary, including stromal cells and granulosa cells, are potential targets of iatrogenic insults. Cancer, Cancer Treatment, and Male Reproductive Function

Normal male reproduction is also dependent on a tightly regulated HPG axis. In males, the pulsatile release of GnRH from the hypothalamus acts on cells within the anterior pituitary gland to stimulate the production and release of FSH. FSH is secreted into the bloodstream and binds to FSH receptors on the basolateral aspect of Sertoli cells within the testicle, which stimulates the production of androgen-binding protein by Sertoli cells and is also responsible for the initiation of spermatogenesis. FSH production is modulated by inhibin B, a glycoprotein produced by the Sertoli cells that feeds back to the hypothalamus and pituitary to suppress FSH production and hypothalamic secretion of GnRH. LH is also produced by gonadotroph cells within the anterior pituitary gland; like FSH, the secretion of LH is regulated by the pulsatile release of GnRH. LH is secreted and stimulates Leydig cells to produce testosterone, and testosterone and FSH act synergistically on the Sertoli cells to initiate and support spermatogenesis. The precise endocrine relationship shared by the hypothalamus, pituitary gland, and testicles is essential for the normal production of sperm. Disturbance of this balance can have detrimental effects on spermatogenesis, resulting in decreased sperm number and quality.

Evidence suggests that cancer itself can affect male reproductive function. For example, at the time of cancer diagnosis, patients often present with impairment of the HPG axis. These findings are commonly noted in men with testicular tumors that produce alpha-fetoprotein (AFP) and beta-human chorionic gonadotropin (β-hCG). Carroll et al reported in 1987 that two-thirds of men with testicular cancer had abnormal FSH, LH, and/or β-hCG levels. Specifically, decreased FSH levels and elevated LH and β-hCG levels were observed in men with poor semen parameters. The study authors asserted that β-hCG might have an inhibitory effect on FSH in some patients, resulting in impaired spermatogenesis. Other etiologic mechanisms have been proposed for the endocrine disruption that is sometimes seen in patients with cancer, including central cytokine effects. While this pathway has been suggested to play a role in oncologic anorexia-cachexia syndrome, it has not been specifically studied. More work is needed to specifically elucidate the mechanisms by which oncologic disease processes disrupt the normal HPG axis. In addition, some literature suggests that semen quality parameters tend to be poorer prior to treatment in men with testicular cancer, leukemia, or lymphoma.

The testis, like the ovary, is both radiosensitive and chemosensitive ( Fig. 37.2 ). Chemotherapy is widely used in the treatment of cancers affecting males, but its cytotoxic effects on healthy tissue can transiently or permanently deplete rapidly dividing cell populations, such as the testicular germinal epithelium. The high mitotic rate of the germinal epithelium within the testis makes it especially vulnerable to the cytotoxic mechanisms of certain chemotherapeutic agents. In contrast, Leydig cells are far more resistant than testicular germ cells to the cytotoxic effect of chemotherapy. As a result, it is more common for a male cancer survivor to experience impaired sperm-making ability while maintaining adequate testosterone production for pubertal progression, libido, and normal sexual function.

Chemotherapeutic regimens that include alkylating agents are among the most gonadotoxic and often lead to permanent oligospermia or azoospermia. These changes in spermatogenesis are typically seen within 90 to 120 days after administration of the alkylating agent. Platinum-based chemotherapy, such as cisplatin and carboplatin, predominately affects spermatogonia and spermatocytes. While most men treated with platinum regimens will experience an associated decline in semen parameters, the majority (80%) will have a return of sperm in the ejaculate within five years of completion of chemotherapy. Antimetabolites such as 5-fluorouracil, methotrexate, gemcitabine, and 6-mercaptopurine can also impair spermatogenesis, although the effects are commonly transient. Clinicians should be mindful of the fact that, while patients might start on a “fertility friendly” chemotherapeutic regimen, transition to other regimens is not uncommon in the course of cancer care. The best time point for sperm cryopreservation to help ensure optimal fertility preservation is prior to the initiation of chemotherapy. ^,

The testis is a highly radiosensitive organ, and radiation-associated declines in semen parameters are commonly seen within 60 to 70 days after radiation treatment. Doses as small as 0.1 Gy can impair spermatogenesis, while doses of just 1.2 Gy have the potential to cause permanent azoospermia. Sperm concentration is typically observed 4 to 6 months after completion of radiation treatment, and recovery of spermatogenesis is often noted within 10 to 24 months. Fractionated radiation regimens result in more pronounced spermatogenesis impairment than nonfractionated regimens; the belief is that repeated injury to the germ cells impairs recovery and further diminishes spermatogonial stem cell and progenitor pools, thus leading to more severe and lasting damage than caused by single, larger doses. In contrast to germ cells, Leydig cells are relatively resistant to radiotherapy. While germinal epithelial damage is observed at low doses of radiation, Leydig cell injury is generally not evident until radiation exposure is 20 Gy or more, at which point serum LH elevation and serum testosterone decline are commonly seen.

In addition to the effects of chemotherapy and radiation therapy, surgical procedures can also lead to iatrogenic impairment of male reproductive potential ( Fig. 37.2 ). Orchiectomy leads to loss of testicular mass and thus germ cell mass, with diminished sperm production capability. Patients undergoing radical prostatectomy for prostate cancer, the most common solid cancer in males, sustain disruption of their excurrent ductal system via the removal of their prostate gland and seminal vesicles. Men being treated with cystoprostatectomy for bladder cancer are at risk for similar excurrent ductal disruption. Retroperitoneal surgery can often result in disruption of the sympathetic nerves that control seminal emission and ejaculation. Retroperitoneal lymph node dissection (RPLND) for men with testicular cancer is one example of this kind of surgery. Template-driven, nerve-sparing approaches are now widely used in the course of RPLND, and these methods represent a technical approach to fertility preservation in males. Finally, pelvic and abdominal exenterative procedures (removal of all or most organs within the pelvic cavity) can necessitate resection of gonadal tissue and/or the components of the excurrent ductal system. If the possibility of such a resection arises during surgical planning, preoperative sperm cryopreservation should be strongly considered.

Additional Adverse Reproductive Outcomes Following Cancer

As described above, cancer and its treatments may lead to infertility or sterility due to premature ovarian failure, oligomenorrhea, uterine dysfunction, or altered endocrine function in females and testicular failure, disruption of the excurrent ductal system, and impaired endocrine function in males. However, there are also a number of other side effects of cancer or its treatment that can alter reproductive function. These effects are often overlooked or dismissed but pose a significant challenge to the reestablishment of a high quality of life in cancer survivors. These include increased depression, psychological disorders, and sexual function issues. Furthermore, patients often report a loss of self-identity or feelings of attractiveness.

It is quite difficult to predict precisely how a given individual’s reproductive potential will be affected by cancer or cancer treatments, as there are many case-dependent variables that contribute to reproductive risk. These factors include but are not limited to a patient’s age, genetic background, medical history, and fertility potential prior to diagnosis and treatment. In addition, the radiation and/or chemotherapy treatment regimen used—including dose, duration, frequency, field of treatment, and combination—has a significant bearing on future reproductive function.

Relevant Sex Differences in Reproduction

Innate biological differences in gametogenesis between males and females have largely dictated the types of fertility preservation methods that are currently available or are being developed. In females, it is commonly accepted that oocyte production ceases during midgestation, resulting in a fixed number of primordial follicle-enclosed oocytes at birth (the ovarian reserve)—approximately 1 million—that set an individual’s reproductive lifespan. The fate of these follicles is to remain quiescent, to activate, or to die. Of those primordial follicles that are activated, only a small fraction will develop to the terminal Graafian follicle stage and produce oocytes that will be ovulated. Once destroyed, there is no mechanism to replace these follicles, as replenishment by ovarian germline stem cells does not appear to be physiologically relevant. By puberty, the primordial follicle number decreases to approximately 400,000, and reproductive senescence occurs at the time of menopause, when approximately 1000 primordial follicles remain in the follicle pool. In addition to having a finite supply, female oocytes also require relatively invasive techniques to access.

In contrast to oocytes, sperm are continuously generated in the adult testis. The process begins when type A pale spermatogonia differentiate into type B spermatogonia. The type B spermatogonia then differentiate into spermatocytes, which undergo meiosis to form spermatids and ultimately mature haploid spermatozoa. This process results in the production of millions of mature sperm daily. Because germline stem cells are very active in the male, there is an increased potential for slow recovery of fertility posttreatment if the spermatogonial stem cells are not irreversibly damaged, and the mitotically quiescent type A dark spermatogonia are able to transform into actively dividing and differentiating type A pale spermatogonia. Compared with oocytes, sperm are numerous and can be obtained using relatively simple and noninvasive methods.

Unlike treatment for adults, there are far fewer fertility preservation options for prepubertal males and females because their gonads are not fully developed. Testes of prepubertal males do not contain mature haploid gametes but instead are populated with spermatogonial stem cells that are poised to initiate spermatogenesis and generate sperm at the onset of puberty. Thus, current fertility preservation treatments in prepubertal boys rely primarily on removing and cryopreserving testicular tissue for potential future use with emerging oncofertility techniques (see sections on Clinical Fertility Preservation Options for Male Patients and Emerging Fertility Preservation Techniques ). Prepubertal females have follicles that develop in waves until the secondary stage but are then eliminated by atresia. It is not until puberty, when cyclic production of gonadotropins promotes the development of follicles to mature stages, that fertilization-competent eggs are ovulated. Thus, prepubertal females cannot make use of most standard fertility-preserving technologies (e.g., hormone stimulation and IVF) that involve the collection of mature gametes. Instead, current fertility preservation treatments for prepubertal females include ovarian tissue cryopreservation and potentially in vitro maturation (IVM) (see sections on Clinical Fertility Preservation Options for Female Patients and Emerging Fertility Preservation Techniques ).

Clinical Fertility Preservation Options for Female Patients

For females, the menu of fertility preservation options is constantly expanding as research breakthroughs are translated into clinical use ( Table 37.3 and Figs. 37.1 and 37.3 ). Although there are many approaches to fertility preservation, the unique set of patient- and case-based factors dictate the best course of action. These factors include a patient’s age, ovarian reserve prior to the start of treatment, and type of cancer, as well as the dose, duration, and timing of cancer therapy. Below is an overview of female fertility preservation options that are currently used clinically ( Table 37.3 and Figs. 37.1 and 37.3 ).