Abstract P1-11-22: Bisphosphonates and Pathologic Complete Response to Neoadjuvant Chemotherapy in Patients with Breast Cancer

Abstract

Abstract Purpose: Several studies have suggested that bisphosphonates have antitumor effects and that their use may have a potential benefit on recurrence and survival in patients with primary breast cancer. In a retrospective study, we sought to evaluate whether the use of bisphosphonates increased the rates of pathological complete response (pCR) in breast cancer patients receiving taxane and anthracycline-based neoadjuvant chemotherapy. Methods: We identified from our database 1449 breast cancer patients receiving taxane and anthracycline-based neoadjuvant chemotherapy between 1995 and 2007 at M.D. Anderson Cancer Center. Among the entire cohort, we identified by chart review those patients that while receiving chemotherapy also received bisphosphonates for a different indication (osteopenia or osteoporosis). Primary outcome was the proportion of patients achieving a pCR. Groups were compared using the chi-squared test. A multivariable logistic regression model was fit to examine the relationship between the use of bisphosphonates and pCR. An exploratory survival analysis using the Kaplan-Meier method was performed; groups were compared using the log-rank test. Results: From the 1449 patients included, 39 (2.7%) received bisphosphonates at the time of neoadjuvant chemotherapy.66.7% received alendronate, 28.2% risedronate and 5.1% ibandronate. Those receiving bisphosphonates were older (P<.001) and less likely to be obese (P=.04). The pCR rate was 26% in the bisphosphonate group and 16% in the non- bisphosphonate group (P=.11). After adjusting for potential confounding variables, patients treated with bisphosphonates tended to have higher rates of pCR (OR 2.16 95% CI 0.89-5.25); however the difference did not reach statistical significance. With a median follow up of 55 months (3-145) there were 412 recurrences and 359 deaths. There were no differences on 5-year PFS (71% vs 80%; P=.28) or 5-year OS (77% vs 82%; P=.42) between the two groups. Conclusions: In this cohort of patients, the concurrent use of bisphosphonates at the time of neoadjuvant chemotherapy was not associated with significant increased rates of pCR. The observed estimates suggest a positive effect; however, it is possible that the small proportion of patients receiving bisphosphonates affected the power to detect a statistically significant difference. To fully test the hypothesis, additional, well-powered prospective studies to evaluate the potential use of bisphosphonates as antitumor agents used in the neoadjuvant setting are warranted. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P1-11-22.