Retrospective analysis of antitumor effects of zoledronic acid in breast cancer patients with bone-only metastases

Abstract

Bisphosphonates have been used successfully in the treatment of hypercalcemia and to reduce skeletal complications of bone metastasis, but have not been shown to prevent bone metastasis or to prolong survival time in metastatic breast cancer patients. The aim of this study was to determine whether the progression-free survival (PFS) and overall survival (OS) of patients with bone-only breast cancer metastasis differed based on whether patients received zoledronic acid, pamidronate, or no bisphosphonate upon diagnosis of their metastases. We retrospectively identified 314 patients diagnosed with bone-only metastasis at the time of initial staging or who developed bone metastasis as the first recurrence site during follow-up from January 1, 1997 to December 31, 2008, at The MD Anderson Cancer Center. Univariate and multivariate Cox hazards models were used to assess the effects of each treatment on PFS and OS. Patients who had more than 1 bone metastasis and Eastern Cooperative Oncology Group (ECOG) performance status of 2 and 3 were more likely to receive zoledronic acid in this analysis. Compared with no bisphosphonate use, the use of zoledronic acid was not significantly associated with longer PFS (hazard ratio [HR] = 0.72, P = .058 in univariate analysis, and HR = 0.80, P = .235 in multivariate analysis) nor with longer OS (HR = 1.04, P = .863 in univariate analysis and HR = 1.34, P = .192 in multivariate analysis). Our study demonstrates that for patients with bone-only metastases, zoledronic acid did not prolong PFS or OS. In patients with bone-only metastasis, we could not demonstrate antitumor effects of zoledronic acid.