Fertility preservation in breast cancer patients: A prospective controlled comparison of ovarian stimulation with tamoxifen and letrozole for embryo cryopreservation

Purpose: To develop safe ovarian stimulation methods to perform in vitro fertilization (IVF) in breast cancer patients who wish to preserve their fertility via embryo cryopreservation before chemotherapy. Patients and Methods: Sixty women (age range, 24 to 43 years) with breast cancer were prospectively studied. Twenty-nine patients underwent 33 ovarian stimulation cycles with either tamoxifen 60 mg/d alone (Tam-IVF) or in combination with low-dose follicle-stimulating hormone (TamFSH-IVF) or letrozole 5 mg in combination with FSH (Letrozole-IVF). After IVF, all resultant embryos were cryopreserved to preserve fertility. Recurrence rates were compared with controls (n = 31) who elected not to undergo IVF. Results: Compared with Tam-IVF, both TamFSH-IVF and Letrozole-IVF patients had greater numbers of follicles (2 ± 0.3 v 6 ± 1 and 7.8 ± 0.9, respectively; P < .0001), mature oocytes (1.5 ± 0.3 v 5.1 ± 1.1 and 8.5 ± 1.6, respectively; P < .001), and embryos (1.3 ± 0.2 v 3.8 ± 0.8 and 5.3 ± 0.8, respectively; P < .001). Peak estradiol (E₂) levels were lower with Letrozole-IVF and Tam-IVF compared with TamFSH-IVF. After 554 ± 31 days (range, 153 to 1,441 days) of follow-up, cancer recurrence rate was similar between IVF and control patients (three of 29 v three of 31 patients, respectively; hazard ratio, 1.5; 95% CI, 0.29 to 7.4), and this estimate was not affected by cancer stage. Conclusion: The combination of low-dose FSH with tamoxifen (TamFSH-IVF) or letrozole (Letrozole-IVF) results in higher embryo yield compared with Tam-IVF. Recurrence rates do not seem to be increased, but the letrozole protocol may be preferred because it results in lower peak E ₂ levels.