High yield of oocytes without an increase in circulating estradiol levels in breast cancer patients treated with follicle-stimulating hormone and aromatase inhibitor in standard gonadotropin-releasing hormone analogue protocols

Background: Adjuvant/neoadjuvant chemotherapy in breast cancer patients may be associated with amenorrhea and a marked reduction in ovarian reserve. Objectives: To assess the use of letrozole with follicle-stimulating hormone (FSH) in gonadotropin-releasing hormone (GnRH) analogue protocols, based on reported attempts to avoid the estradiol (E2) increase during controlled ovarian hyperstimulation for embryo cryopreservation in breast cancer patients using a combination of low dose FSH and aromatase inhibitor (letrozole) in a GnRH-antagonist protocol. Methods: Twenty-four breast cancer patients were treated with recombinant FSH (150-450 U/day) and letrozole (5 mg/day) in a long GnRH-agonist (n=7) or GnRH-antagonist (n=17) protocol. After oocyte retrieval, insemination and/ or intracytoplasmic sperm injection was performed. The embryos were frozen. Results: The average interval from surgery to oocyte retrieval was 40 days. Average duration of treatment was 9.6 days and mean peak E2 level 1342 ± 1091 pmol/L, yielding 16.0 ± 16.3 oocytes (range 0-82). Mean fertilization rate was 69.5 ± 20.4% and mean number of embryos cryopreserved 10.3 ± 9.3. More oocytes were retrieved with the long GnRH protocol, but the difference was not statistically significant (24.8 ± 24.6 vs. 12.0 ± 8.8 pmol/L, P = 0.07). Conclusions: As previously reported, ovarian stimulation with letrozole and FSH, in both the long GnRH-agonist and GnRH-antagonist protocols, is apparently effective in breast cancer patients and spares them exposure to high E2 levels.