Controlled ovarian hyperstimulation with or without letrozole for fertility preservation in breast cancer patients: study protocol for a randomised controlled trial

Introduction: Multimodal anticancer therapies greatly damage the fertility of breast cancer patients, which raises urgent demand for fertility preservation. The standard options for fertility preservation are oocyte and embryo cryopreservation; both require controlled ovarian hyperstimulation (COH). However, there are safety concerns regarding breast cancer relapse due to the elevated serum estradiol levels during COH. Serum estradiol levels can be effectively decreased with the highly specific aromatase inhibitor letrozole. Letrozole is still uncommonly used during COH for fertility preservation, which has only been reported in a few studies, and the evidence of oocyte retrieval during ovarian stimulation and short-term safety from the perspective study is insufficient. As a result, this study will compare the efficacy of ovarian stimulation and the short-term safety of letrozole COH and non-letrozole COH protocols for preserving fertility in patients with breast cancer.

Methods and analysis: This is an open-label, multicentre RCT being conducted in five Chinese reproductive medical centres. 64 eligible patients diagnosed with breast cancer will be randomly assigned (1:1) to the letrozole or non-letrozole group during their COH cycles. The primary outcome is the number of mature oocytes. The secondary outcomes are the number of high-quality embryos, incidence of ovarian hyperstimulation syndrome(OHSS) and recurrence rate of breast cancer.

Ethics and dissemination: Ethical approval was obtained from the Ethics Review Committee of Guangdong Provincial People's Hospital (KY-Q-2023-840-02). Written informed consent will be obtained from each participant. Findings will be disseminated to patients, clinicians and commissioning groups through peer-reviewed publications.

Trial registration number: ChiCTR2300078625.