The idea that bisphosphonates have the potential to impact breast cancer recurrence has been discussed for many years, states Edith A. Perez, MD, deputy director, Mayo Clinic Cancer Center, Florida, director, Breast Program, Serene M. and Frances C. Durling Professor of Medicine, Mayo Medical School.

The phase III B-34 study investigated the oral bisphosphonate clodronate in a progressive, randomized, double-blind, placebo controlled study. The primary endpoint of the trial was disease-free survival with a secondary endpoint focusing on the incidence of skeletal metastases, overall survival, relapse-free survival, non-skeletal metastases, and skeletal morbid events.

Perez, one of the authors of the study, notes that the results of the trial were interesting and that overall there was not a significant difference observed between the two arms. The results demonstrated that clodronate may perform better in a subset of patients that are 50 years or older. This older subset of patients demonstrated a decreased risk for breast cancer recurrence in other sites besides the bone, which was unexpected for a bisphosphonate.

The findings of the trial suggested that further investigation is needed in postmenopausal women. Several bone-targeting drugs are available such as clodronate, zoledronic acid, and denosumab, a RANK ligand inhibitor. The B-34 trial supports the need for further analysis into bisphosphonates to prevent breast cancer recurrence.