Perrone F, et al. - Among premenopausal patients who have breast cancer with hormone receptor-positive (HR+) tumors, researchers investigated if letrozole (L) and zoledronic acid plus L (ZL) are more efficacious than tamoxifen (T) when given as adjuvant endocrine therapy. In a phase 3 trial, triptorelin was administered to suppress ovarian function in 1,065 premenopausal patients with HR + early breast cancer and these patients randomly received (1:1:1) adjuvant T, L or ZL for 5 years. In the HOBOE study, significantly improved DFS but worsened compliance and toxicity were observed in relation to administration of ZL vs T in premenopausal patients with early breast cancer undergoing ovarian function suppression with triptorelin. The disease-free rate at 5 years was 85.4%, 93.2% and 93.3% with T, L and ZL, respectively, after a 64-month median follow-up and 134 reported events. After starting treatment with T, L or ZL, it was stopped for toxicity or refusal in 7.3%, 7.3% and 16.6% of patients and grade 3–4 side-effects were reported in 4.2%, 6.9% and 9.1% patients in the safety population, respectively.