Study protocol: Randomized, open-label, non-inferiority clinical trial for evaluating the clinical and pathological response rates to neoadjuvant hormone therapy and chemotherapy in patients with luminal-subtype breast tumors.

Background: Despite neoadjuvant hormone therapy (NHT) is being underused, it is an effective treatment for luminal tumors at a lower cost and with fewer side effects compared to those associated with neoadjuvant chemotherapy (NCT). The lack of robust comparative data between NHT and NCT is a factor that limits its use in clinical practice. Methods: This study will be a randomized, open-label, non-inferiority clinical trial. Patients diagnosed with HER2-negative luminal-subtype breast cancer will be identified at the time of diagnosis. Menopausal patients randomized for NHT should receive anastrozole for at least six months. Premenopausal women should receive anastrozole associated with subcutaneous goserelin acetate every 12 weeks for at least six months. Patients randomized for NCT will receive a standard institutional regimen based on anthracyclines and taxanes. Sample size was calculated considering the CPS + EG as a method for evaluating response and prognosis, where a score <3 was defined as good. The non-inferiority margin for NHT was set at 15%. The study considered a power of 80%, a significance level of 5%, and an outcome proportion in each group of 69%, resulting in 118 patients in each group. We estimated at 10% of losses, resulting in a sample of 130 patients in each group. Conclusion: The non-inferiority of NHT in relation to NCT will provide further evidence that replacing NCT with NHT is safe and effective in eligible patients, which is particularly relevant for populations with limited access to health services and for institutions with few available resources.