Fertility and Breast Cancer

Breast cancer (BC) is the most common malignancy diagnosed in women of child-bearing age, accounting for approximately 5% of new cancer cases in the US each year [1]. With the steady increase of childbearing age in the last two decades, approximately 50% of young women with BC will not have started or completed their families at the time of diagnosis [2]. In the face of a BC diagnosis, women who desire to become a biological mother in the future face the complex decision of whether to undergo fertility preservation before treatment. Fertility following BC treatment will be dictated by many factors including ovarian reserve, the age of the patient, the choice of systemic treatment, and the interventions pursued prior to gonadotoxic therapy [3, 4].

Patient Counseling at the Time of Diagnosis

Following an abnormal mammogram, ultrasound, or MRI, breast cancer can be diagnosed with a percutaneous biopsy. Once the patient is diagnosed, the patient is often referred to a breast surgeon or medical oncologist. While cancer diagnosis and treatment are the primary focus of a patient’s initial consultation, the treating clinician should also prioritize the discussion of future fertility with appropriate premenopausal patients. Given the timing to breast cancer treatment, in most cases, fertility preservation can be safely performed prior to the initiation of any oncologic management. In the setting of fertility preservation, overall survival, disease free survival, and local recurrence do not appear to be impacted by the time to initiation of first oncologic treatment [5].

Breast surgeons with knowledge of oncofertility are more likely to discuss their patients’ fertility treatment plans, resulting in more referrals to specialty care [6]. A study published by Letourneau et al. in 2012 showed that BC patients who received counseling focused on fertility preservation and future pregnancy experienced less regret and a better quality of life [2]. Studies have also shown that when providers discuss fertility options with their premenopausal cancer patients, a large majority (up to 89%) of those patients seek further information [7••]. Another study by Jeruss et al. demonstrated that BC patients may choose not to initiate treatment or experience decreased treatment adherence because of fertility concerns [8]. Oncofertility decision aids and success rate calculators have been created to assist patients in the decision-making process surrounding fertility and cancer and are available online at the following websites:

Breast Surgery and Fertility

Breast surgery itself will not affect future fertility but may affect lactation. Bilateral mastectomy will impede breastfeeding, but if the surgery is a unilateral mastectomy, segmental mastectomy, or a lumpectomy, the patient may still be able to lactate sufficiently [9]. Most breast conservation surgery will involve only one quadrant of the breast, sparing the majority of the architectural structure of the milk ducts, though radiation treatment could impact milk production. In rare instances, such as in Paget’s disease, central lumpectomy is the treatment of choice and lactation will not be possible.

Radiation and Fertility

Several trials have demonstrated the importance of radiation therapy after breast conservation surgery for the treatment of breast cancer. The National Surgical Adjuvant Breast Project (NSABP) B-06 study twenty-year follow-up revealed lower recurrence rates when comparing breast conservation surgery followed by breast irradiation (BI) (14.3%) with breast conservation surgery alone (39.2%) [10]. Breast irradiation is therefore an important aspect of breast cancer therapy. BI is a localized modality of treatment and generates minimal exposure to intrathoracic organs and very minimal to no exposure to the abdominal cavity. Targeted BI should not significantly affect ovarian reserve and future fertility [11], though it may affect lactation. New radiation accelerators also allow computed tomography planning integration to minimize radiation injury to adjacent structures.

Lactation can be successful after BI [12] and when the contralateral (non-irradiated) breast is used. After BI, 50% of patients still are able to use the ipsilateral (radiated) breast for breastfeeding, but 80% reported a comparative decrease in milk output [12].

Ovarian Function and Assessing Ovarian Reserve

In order to understand ovarian reserve and its impact on fertility, it is important to understand folliculogenesis and ovulation. Folliculogenesis—the development of a follicle in preparation for ovulation—is a complex physiologic process. During fetal development, a woman forms a limited number of primordial follicles, which consist of a single oocyte surrounded by a single layer of flattened granulosa cells. At birth, the ovary contains approximately 1 million oocytes, dropping to 300,000-500,000 at puberty and 1000 by menopause [13, 14]. Once menarche has occurred, a limited number of primordial follicles are triggered to mature at the start of each menstrual cycle. Through timed patterns of hormonal release, a primordial follicle transitions into a mature ovarian follicle or Graafian follicle. This mature ovarian follicle will then take one of two paths: ovulation in anticipation of fertilization or atresia. It takes approximately one year for a primordial follicle to develop to the ovulatory stage [15] (see Fig. 1).

Fig. 1
figure 1

Fertility preservation methods in cancer therapy

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There is typically one dominant follicle that completes maturation and releases an ovum, and the others regress and eventually deteriorate. Pituitary follicle stimulating hormone (FSH) stimulates a single follicle to outcompete the other developing follicles. The dominant follicle rapidly grows into a secondary follicle with a defined outer layer called the theca interna, which contributes to the production of estradiol. Rising estradiol levels ultimately trigger a surge in luteinizing hormone (LH) and the release of the ovum from the dominant follicle. After release, the follicle regresses into a steroidogenic complex known as the corpus luteum. The corpus luteum secretes important hormones, particularly progesterone in anticipation of supporting a developing pregnancy.

Any rapidly dividing cell is harmed by chemotoxic agents, and ovarian follicles are particularly sensitive to chemotherapy. Prior to therapy, ovarian reserve is extremely variable among patients, and there is no direct way to measure how many follicles remain in an ovary. Two indirect ways to measure ovarian reserve include antral follicle count and anti-mullerian hormone (AMH) levels. Antral follicle counts can be done with a trans-vaginal ultrasound. While primordial follicles are not visible to the naked eye, follicles recruited for maturation can be visualized on ultrasound as fluid filled antral follicles measuring 2-10mm. This method indicates ovarian activity, but does not fully estimate future ovarian function.

AMH is a hormone that rises at the beginning of follicular development. Granulosa cells and antral follicles are mainly responsible for the production of AMH. AMH is used to estimate ovarian reserve and could be considered a marker of ovarian function before and after chemotherapy [16, 17]. During chemotherapy, AMH levels fall steadily becoming undetectable in 50% of the patients. For therapies with lower gonadotoxicity, AMH may recover, and women may resume normal menses. However, the resumption of menses does not entirely indicate return of ovarian function nor does it predict future fertility [18]. Although it is not a perfect test, AMH is the preferable laboratory test to measure ovarian function recovery following treatment. AMH does not fluctuate with the menstrual cycle or hormonal manipulation [19]. For chemotherapies that have high levels of gonadotoxicity, AMH will often become undetectable and will not recover [16].

Ovarian Injury in Chemotherapy

First line systemic BC therapy damages the DNA of the oocytes, impairing cell repair and leading to apoptosis [20]. Unfortunately, there are no first-line chemotherapy regimens for BC that completely spare the ovaries from toxicity. Each class of antineoplastic agent has a distinct action on cancer cells resulting in the arrest of cell division (Table 1). The National Surgical Adjuvant Breast and Bowel Project (NSABP) B-15 [28] and B-16 [28] studies established current preferred first lines regimens including doxorubicin and cyclophosphamide in BC with metastatic nodal disease. These agents had equivalent results and were better tolerated than cyclophosphamide, methotrexate, and 5-fluorouracil. The addition of paclitaxel to doxorubicin and cyclophosphamide was evaluated and proved to increase disease free survival and also overall survival [27]. All of these agents have varying levels of gonadotoxicity (see Table 1).

Table 1 Most common chemotherapy agents for breast cancer treatment
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Apoptosis, caused by DNA damage, is the most common mechanism of ovarian cell demise caused by DNA damage. Double-stranded breaks are the most harmful type of injury to the ovarian cells and are common results of gonadotoxic therapies. The oocyte initially attempts to repair the DNA through the ataxia telangiectasia mutated (ATM)-mediated DNA damage repair pathway. If the cell cannot be repaired, apoptosis will occur [32]. The administration of antineoplastic agents is also associated with a sharp reduction in ovarian blood volume and spasm of small vessels in the ovary [33]. Chronic spasm and vascular flow deregulation ultimately lead to fibrosis of the ovarian cortex [32].

Anti-Hormonal Therapy and Fertility

One important agent for breast cancer treatment, trastuzumab, does not appear to affect ovarian reserve. This monoclonal antibody targets breast cancers with HER2/neu receptor over-expression. Treatment with trastuzumab is contraindicated in pregnancy as this agent is considered a teratogen [29].

Anti-hormonal therapies including tamoxifen and aromatase inhibitors have also become mainstays of adjuvant treatment for hormone receptor positive breast cancer. In premenopausal women, a five- to ten-year tamoxifen treatment regimen is recommended. Tamoxifen is considered a teratogen, and its use is contraindicated during pregnancy [34]. Patients receiving a recommendation for tamoxifen therapy may desire to delay their treatment or take a closely monitored hiatus from treatment in order to pursue pregnancy, but the safety of such approach is unknown. The IBCSG 48-14 POSITIVE trial is evaluating the safety of interruption in anti-hormonal treatment in order to pursue pregnancy [35]. Clarification of the temporary hiatus will be available with the POSITIVE trial results.

Fertility Preservation Options

Options are available for cancer patients who desire to pursue pregnancy after treatment (see Fig. 1). Many of these options require fertility preservation prior to systemic therapy and should be discussed as early as possible in the patient’s treatment course. Women of advanced reproductive age or limited ovarian reserve should be carefully counseled before the application of any fertility preserving or fertilization techniques. The rates of successful live birth drop significantly after the age of 42 (24% success rate) compared with patients younger than 35 years of age (45% success rate) [36]. Realistic expectations must be set to avoid frustration, disappointment, and unnecessary costly procedures.

Oocyte or Embryo Cryopreservation

Oocyte/embryo cryopreservation is considered the gold standard for BC patients trying to achieve fertility preservation. In recent years, advances in the rapid vitrification process have led to outcomes similar to fresh embryos used for traditional in vitro fertilization procedures (IVF) [37]. In order to harvest oocytes for preservation, patients typically undergo controlled ovarian stimulation (COS). COS can be started at any point in the menstrual cycle, known as random start protocol, minimizing the time needed for fertility preservation and the delay in systemic therapy or breast surgery [38,39,40,41]. Successful COS and oocyte harvesting can be performed over a two-week period. In non-BC patients, ovarian stimulation protocols induce high levels of circulating estrogen. COS protocols for patients with BC include a gonadotropin (recombinant follicle-stimulating hormone or urinary human menopausal gonadotropin) combined with an aromatase inhibitor (AI), most commonly letrozole. The use of an aromatase inhibitor results in lower levels of circulating estrogen with similar ovarian stimulation results to traditional ovarian stimulation modalities. These agents stimulate multiple fluid-filled ovarian follicles to form without releasing their oocytes [37]. Following stimulation, oocytes are retrieved transvaginally using ultrasound guidance. Mature oocytes are frozen without being fertilized or are fertilized with a partner or donor sperm to create embryos. Embryos may be used or frozen at fertilization, day three, or day five. Live birth rates and perinatal outcomes are the equivalent between frozen embryos and frozen oocyte-derived embryo transfers (≅25%) [42]. Embryos five days and older can be genetically analyzed to rule out genetic mutations, such as BRCA, PALB2, and ATM. Among different biological tumor profiles, triple-negative breast cancer patients have lower numbers of mature oocytes when compared with hormonal positive patients after COS [43••].

Ovarian Tissue Cryopreservation and Transplantation

Ovarian tissue cryopreservation (OTC) is an active area of research and may be a reasonable option for selected patients. It is also the only option for fertility preservation in prepubertal patients with cancer. The procedure to harvest ovarian tissue is typically performed laparoscopically. This tissue may comprise the entire ovary or just strips of tissue. The tissue is subsequently cryopreserved offering the potential for thousands of follicles to be fertilized in the future. Whenever motherhood is desired, autologous transplantation of the tissue can be performed in order to mature the oocytes within the ovarian tissue in preparation for subsequent fertilization. In a recently published meta-analysis, a cumulative clinical birth of 57.5% has been reported for cryopreserved ovarian tissue [44••].

Aside from the invasiveness of this process, the biggest disadvantage is the risk of reseeding of potential malignant cells during autologous transplantation, especially in patients with oncogenic genetic mutations. The use of retrievable hydrogels may be a novel way to reduce the likelihood that malignant cells will be re-seeded [45]. This promising, experimental technique involves the encapsulation of nascent follicles from ovarian tissue using alginate hydrogels. Future heterotopic transplantation of the encapsulated follicles is performed in order to allow the nascent follicles to be exposed to the hormonal milieu necessary for follicular maturation and subsequent fertilization. The use of these hydrogels, which separate nascent follicles from harvested ovarian tissue, decreases the risk of re-introducing malignant cells upon reimplantation [45].

Encapsulated In Vitro Follicle Growth (eIVFG)

Encapsulated in vitro follicle growth (eIVFG) is the harvest of immature oocytes transvaginally or from OTC material for later use in in vitro fertilization process [46••]. The growth of ovarian follicles in biomaterials such as alginate is important to the provision of supporting matrices that allow follicles to mature outside the body. Live birth has been accomplished in mice from eIVFG and from follicles enclosed in an ovarian bioprosthetic. These future uses for the ovarian tissue that has been cryopreserved provide hope for patients, especially pediatric patients, for fertility restoration in future years.

Ovarian Suppression

Another method of ovarian preservation includes ovarian suppression with gonadotropin-releasing hormone agonists (GnRHa), such as leuprolide. Using GnRHa for chemical ovarian protection in cancer patients has been studied and extensively debated. The 2020.1 National Comprehensive Cancer Network (NCCN) and The American Society of Clinical Oncology (ASCO) Guidelines endorsed the use of GnRHa [24, 47] to preserve ovarian function and diminish the likelihood of chemotherapy induced amenorrhea. Recent studies suggest a 16.8% absolute reduction in premature ovarian failure when GnRHa was administered concomitantly with chemotherapy [48]. However, many of these patients will still experience ovarian failure, and GnRHa’s should not be used with the intent to ensure future fertility. These drugs are a tool that can be used to protect the remaining ovarian tissue during systemic treatment, but they do not support normal reproductive function after treatment.

A variety of different mechanisms of GnRHa have been hypothesized to contribute to ovarian protection. There is some thought that GnRHa recreates the prepubertal hypogonadotropic milieu, leading the ovary to a quiescent prepubertal state [49, 50]. GnRHa also decreases estrogen levels and decreases ovarian perfusion, limiting ovarian exposure to chemotherapeutic agents [51]. GnRHa may also have a direct effect mediated through receptors in the ovary [52, 53]. An anti-apoptotic molecule, sphingosine-1-phosphate (S1P), is upregulated with GnRHa administration. This molecule inhibits the ceramide pathway and is implicated in chemotherapy induced apoptosis of the ovary [52,53,54]. GnRHa may also protect the ovarian germinative stem cells. These ovarian stem cells may be able to reconstitute the primordial follicle pool following the administration of gonadotoxic agents [55, 56]. Another mechanism may involve the antiapoptotic action that GnRHa have been shown to have on cumulus cells [57••].

The suppression ovarian function trial (SOFT) and the Tamoxifen and Exemestane Trial (TEXT) demonstrated superior cancer outcomes when ovarian suppression was added to anti-hormonal therapy for premenopausal patients with breast cancer [58]. Disease free survival was 83.2% for the group that received tamoxifen and ovarian suppression, 85.9% for the group that received exemestane, and ovarian suppression versus 78.9% for the group that received tamoxifen alone [58]. While ovarian suppression was shown to be a tool in patients with hormonal positive cancers, fertility preservation was not a major outcome of this trial. Ovarian suppression was performed with triptorelin 3.75 mg by intramuscular injection, or bilateral oophorectomy, or ovarian irradiation. Thus, the mechanism of action and indeed the value of GnRHa remain to be proven as a categorical way in which fertility can be spared.

Future Perspectives

Sphingosine-1-phosphate (S1P) is an important cell mediator and functions through cellular proliferation, angiogenesis, and cytoskeleton reordering [59, 60]. This protein may hold potential for ovarian protection and preservation in cancer patients receiving systemic therapy. S1P promotes corpus luteum development and steroid synthesis and also plays a major role as a cytoprotective for ovarian follicles by protecting luteinized granulosa cells from apoptosis [61]. Studies have shown that S1P treatment of human ovarian tissue transplanted to mouse ovaries reduces the number of apoptotic cells when exposed to cyclophosphamide or doxorubicin and may be useful during cryopreservation and chemotherapy [61,62,63,64,65]. Rodent studies demonstrated that the administration of S1P intravenously decreases the effects of ovarian toxicity when receiving cyclophosphamide and cisplatin. Pre-treatment with S1P in mice receiving dacarbazine increases preantral follicle count and the number of pregnancies [66]. In another study, S1P-treated vitrified ovaries have a lower mRNA expression of caspase 3 and c-myc. Caspase 3 is considered an “executioner” caspase, coordinating DNA fragmentation during apoptosis. Decreasing c-myc production and therefore decreasing apoptosis enzymes leads to increased primordial follicles during the vitrification process [67,68,69]. S1P-treated ovaries of bovine, sheep, and rhesus monkeys had reverse radiation effects, increased the activation of primordial follicles, and promoted the survival of granulosa cells [70,71,72]. Unfortunately, S1P is oncogenic and has also been implicated on the migration, proliferation, and vascular development of tumor cells [73,74,75]. Its concentration has been noted to be increased in patients with ovarian cancer, and levels drop when the cancer is removed [76]. So, while S1P is not a good therapeutic, these studies point toward a mechanism that could be utilized in the future.

Conclusion

Breast cancer can alter the course of a woman’s life, but in premenopausal women desiring fertility, there are tools available to mitigate the negative impact of this diagnosis. Strategies for fertility preservation in women diagnosed with BC are available and continue to advance. Breast surgeons and oncologists should become comfortable with the options available to their patients, and their counseling and treatment algorithms should include oncofertility as an essential component. Fertility preservation options should be discussed with the patient at the time of the diagnosis, and hospitals should seek to ensure the availability of these services to patients in need.