Use of bisphosphonates (Bis) combined with sunitinib (Su) to improve the response rate (RR), progression-free survival (PFS), and overall survival (OS) of patients (pts) with bone metastases (mets) from renal cell carcinoma (RCC).

Abstract

4619 Background: Bis are used to prevent skeletal events of bone mets, and may exhibit anti tumor effects. We aimed to evaluate whether Bis can bring a RR, PFS, and OS benefit to pts with bone mets from RCC that are treated with Su. Methods: We performed an international multicenter retrospective study of pts with bone mets from RCC who were treated with Su. Pts were divided into Bis users (group 1) and nonusers (group 2). The effect of Bis on RR, PFS and OS, was tested with adjustment for known prognostic factors using a chisquare test from contingency table and partial likelihood test from Cox regression model. Results: Between 2004-2011, 244 pts with metastatic RCC were treated with Su. 92 pts had bone mets, 41 group 1 and 51 group 2. The groups were balanced regarding the following known prognostic factors: past nephrectomy, clear cell vs non clear cell histology, initial diagnosis to sunitinib treatment (tx) time, presence of ≥ 2 mets sites, presence of lung/liver mets, ECOG performance status, anemia, calcium level > 10 mg/dL, elevated alkaline phosphatase (AP), pre-tx neutrophil to lymphocyte ratio (NLR) >3, sunitinib induced HTN, and the use of angiotensin system inhibitors. They were also balanced with regard to past cytokines/targeted tx, and mean sunitinib dose/cycle. Objective response was partial response/stable disease 85% (n=35) vs 71% (n=36), and progressive disease 15% (n=6) vs 29% (n=15) (OR 3.287, p=0.07) in group 1 vs 2 respectively. Median PFS was 15 vs 5 months (HR 0.433, p=0.035), and median OS not reached with a median folloup time of 43 mos vs 12 months (HR 0.398, p=0.003), in favor of group 1. In multivariate analysis of the entire pt cohort (n=92), factors associated with PFS were Bis use (HR 0.433, p=0.035), pre-tx NLR ≤3 (HR 0.405, p=0.016), and elevated AP (HR=3.63, p=0.012). Factors associated with OS were Bis use (HR 0.32, p=0.003), elevated AP (HR 3.18, p=0.002), and Su induced HTN (HR 0.193, p< 0.001). Conclusions: Bis may improve the outcome of Su tx in RCC with bone mets. This should be investigated prospectively, and if validated applied in clinical practice and clinical trials.