Long-term outcomes of prolonged bisphosphonates more than 2 years in bone metastatic breast cancer: risk vs benefit

Background Bisphosphonates are the mainstay therapeutic options for prevention of skeletal-related events and generally used for up to 2 years in bone metastatic cancer patients. Aim We aimed to evaluate the long-term outcomes of prolonged (> 2 years) bisphosphonate usage in bone metastatic breast cancer (BMBC) patients. Methods Ninety-nine BMBC patients who had prolonged bisphosphonates were evaluated retrospectively for long-term outcomes and survival rates. Results Median duration of bisphosphonate therapy was 46.8 (24-198) months. Seven patients had bisphosphonate-related adverse events (osteonecrosis of the jaw (ONJ) (n= 6), ONJ and renal failure (n= 1)). Bisphosphonate was switched to another one because of bone metastasis progression in more than one-third of the patients (n= 36, 36.3%). The patients who had bisphosphonate switch therapy had statistically significant longer overall survival (p< 0.01). Neither duration nor type of bisphosphonates had effect on frequency of bisphosphonate-related adverse events. Conclusion Bisphosphonates might be prolonged for more than 2 years in BMBC patients with an acceptable toxicity profile. In addition, bisphosphonates switch therapy should be preferred in those with progressive bone metastasis since it might contribute to better survival despite bisphosphonates could not have been shown to have survival benefit in previous studies.