Strontium-89 Therapy for Breast Cancer Bone Metastases: Pain Relief Effects and Predictive Factors

In this study, we evaluate the analgesic effect of strontium-89 (Sr-89) for patients with breast cancer having multiple bone metastases and identify positive predictive factors. We retrospectively evaluated 15 patients who were administered Sr-89 for painful bone metastases from breast cancer at St. Marianna University Hospital between January 2010 and April 2014. For patients receiving multiple doses, only the first dose was evaluated. Pain relief was defined as a decrease in the score of the Numeric Rating Scale (NRS) or requirement of reduced doses of pain medication 1 - 2 months after being on Sr-89 administration. The associations between pain relief owing to Sr-89 and that owing to bone scan index, interval from bone metastasis onset to Sr-89 administration, zoledronate and denosumab treatment history, hormone therapy/aromatase inhibitor history, and chemotherapy history were assessed. A logistic model was used for statistical analysis. Pain relief was observed in 11 (73.3%) of 15 patients. No statistically significant value was observed between pain relief and bone scan index, interval from bone metastasis onset to Sr-89 administration, zoledronate and denosumab treatment history, hormone therapy/aromatase inhibitor history, and chemotherapy. Thus, Sr-89 was effective for 70% of patients with breast cancer bone metastases, although positive predictive factors for pain relief could not be determined.