Effect of antihistamines on recurrence-free survival of patients with early-stage breast cancer treated with radiotherapy

Background: Breast cancer is a global health problem. Histamine may stimulate cancer growth, while its inhibition leads to reduced cellular proliferation and increased apoptosis and cellular senescence. Consequently, histamine receptors may be potential therapeutic targets. This study aimed to analyze the effect of antihistamines on long-term local control of patients with early-stage breast cancer treated with radiotherapy. Materials and methods: An observational cohort study was conducted and included patients with early-stage breast cancer treated with radiotherapy (RT) between 2012 and 2020. Patients were divided into a control group and an antihistamine (H1 or H2) use group. The primary endpoint was recurrence-free survival (RFS) and the secondary outcome was overall survival (OS); both were analyzed using Kaplan–Meier curves, and differences were assessed with the log-rank test. Results: A total of 386 patients were analyzed, 185 in the control group and 201 in the antihistamine group, with a median follow-up of 120 months. Ten-year RFS was significantly better in the antihistamine group, at 93% vs. 88% in the control group (p < 0.05), with the benefit maintained in patients treated with a conventional RT schedule, those with clinical stage I disease, and those with a luminal molecular profile; ten-year OS was 97.36% in the control group vs. 99.35% in the intervention group, with no difference between groups. Conclusions: The use of H1 or H2 antihistamines was associated with improved recurrence-free survival in patients with early-stage breast cancer treated with radiotherapy. It is imperative to analyze patients with advanced-stage disease in a randomized prospective trial.