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PurposeAfter chemotherapy for breast cancer, most women will recover some ovarian function, but the timing and extent of this recovery are poorly understood. We studied post-chemotherapy ovarian recovery in women with and without a history of ovarian suppression during chemotherapy.MethodsReproductive age breast cancer patients who were seen prior to chemotherapy for fertility preservation consult were consented for follow-up ovarian function assessment (every 3-6 months after chemotherapy) with antral follicle count (AFC) in this prospective cohort study. We restricted our analysis to those with menses present after chemotherapy. Box plots were used to demonstrate the change in follow-up AFC versus time elapsed after chemotherapy. A mixed effects regression model was used to assess differences in AFC.ResultsEighty-eight patients with a history of newly diagnosed breast cancer were included. Forty-five patients (51%) had ovarian suppression with GnRH agonist (GnRHa) during chemotherapy. AFC recovery appeared to plateau at 1 year after completing chemotherapy at a median of 40% of pre-chemotherapy AFC. After adjustment for age, initial AFC, cyclophosphamide exposure, combined hormonal contraceptive (CHC) use, and tamoxifen use, AFC recovered faster and to a greater degree for those women who underwent GnRHa therapy for ovarian protection during chemotherapy (P = 0.032).ConclusionsWomen with menses after chemotherapy for breast cancer appear to recover their full potential AFC 1 year after their last chemotherapy dose. Treatment with GnRHa during chemotherapy is associated with a higher degree of AFC recovery. The findings of this study can aid in counseling patients prior to chemotherapy about expectations for ovarian recovery and planning post-treatment fertility preservation care to maximize reproductive potential when pre-treatment fertility preservation care is not possible or has limited oocyte yield.

While mutations in the fragile X mental retardation-1 (FMR1) gene are associated with varying reproductive outcomes in females, the effects of a complete lack of FMR1 expression are not known. Here, we studied the ovarian and reproductive phenotypes in an Fmr1 knockout (KO) mouse model and the role of mammalian target of rapamycin (mTOR) signaling. Breeding, histologic and mTOR signaling data were obtained at multiple time points in KO and wild type (WT) mice fed a control or rapamycin (mTOR inhibitor) diet. KO mice showed an earlier decline in ovarian reserve than WT mice with an increased proportion of activated follicles. mTOR and phosphorylated S6 kinase (p-S6K) levels, a measure of downstream mTOR signaling, were elevated in the KO ovaries. Rapamycin blocked these effects in KO mice, and increased the primordial follicle pool and age of last litter in WT mice. Our data demonstrates an early decline in reproductive capacity in Fmr1 KO mice and proposes that premature recruitment of the primordial pool via altered mTOR signaling may be the mechanism. Reversal of phenotypes and protein levels in rapamycin-treated KO mice, as well as increased reproductive lifespan of rapamycin-fed WT mice, suggest the mTOR pathway as a potential therapeutic target.

While mutations in the fragile X mental retardation-1 (FMR1) gene are associated with varying reproductive outcomes in females, the effects of a complete lack of FMR1 expression are not known. Here, we studied the ovarian and reproductive phenotypes in an Fmr1 knockout (KO) mouse model and the role of mammalian target of rapamycin (mTOR) signaling. Breeding, histologic and mTOR signaling data were obtained at multiple time points in KO and wild type (WT) mice fed a control or rapamycin (mTOR inhibitor) diet. KO mice showed an earlier decline in ovarian reserve than WT mice with an increased proportion of activated follicles. mTOR and phosphorylated S6 kinase (p-S6K) levels, a measure of downstream mTOR signaling, were elevated in the KO ovaries. Rapamycin blocked these effects in KO mice, and increased the primordial follicle pool and age of last litter in WT mice. Our data demonstrates an early decline in reproductive capacity in Fmr1 KO mice and proposes that premature recruitment of the primordial pool via altered mTOR signaling may be the mechanism. Reversal of phenotypes and protein levels in rapamycin-treated KO mice, as well as increased reproductive lifespan of rapamycin-fed WT mice, suggest the mTOR pathway as a potential therapeutic target.