Tamoxifen co-administration during controlled ovarian hyperstimulation for in vitro fertilization in breast cancer patients increases the safety of fertility-preservation treatment strategies

Objective To evaluate the safety and efficacy of tamoxifen co-administration during conventional controlled ovarian hyperstimulation (COH) protocols for a fertility-preservation IVF cycle in breast cancer patients. Design Two groups: retrospective descriptive cohort study and prospective study. Setting Breast cancer oncology and fertility-preservation centers in a tertiary hospital. Patient(s) Two groups of breast cancer patients: premenopausal patients treated with adjuvant tamoxifen; and patients undergoing in vitro fertilization (IVF) for fertility preservation. Intervention(s) Fertility-preservation cycles, tamoxifen co-administration during conventional IVF. Main Outcome Measure(s) Endocrine records, and IVF results. Result(s) Estradiol (E₂) levels were chronically high (mean 2663 pmol/L, maximum: 10,000 pmol/L) in 38 of 46 breast cancer patients treated with adjuvant tamoxifen. Co-administration of tamoxifen (48 cycles) during conventional IVF or without tamoxifen (26 cycles), using either the long gonadotropin-releasing hormone-agonist or-antagonist protocols, resulted, respectively, in a mean of 12.65 and 10.2 oocytes retrieved, and 8.5 and 6.4 embryos cryopreserved. Average peak E₂ levels were 6,924 pmol/L and 5,093 pmol/L, respectively, but long-term recurrence risk (up to 10 years) was not increased. Conclusion(s) In breast cancer patients, co-administration of tamoxifen during conventional COH for fertility preservation does not interfere with IVF results. The high serum E₂ levels during COH should be considered safe, as it simulates the high prevalence of persistently high serum E₂ levels in premenopausal breast cancer patients safely treated with adjuvant tamoxifen.