Significance of zoledronic acid on survival in patients with bone metastases from renal cell carcinoma.

Abstract

374 Background: It remains unclear whether zoledronic acid (ZOL) improves overall survival (OS) for renal cell carcinoma (RCC) patients with bone metastases. We retrospectively investigated the clinical benefit of ZOL for OS in RCC patients with bone metastases. Methods: Between 1978 and 2010, 77 patients who had RCC metastatic to bone were treated in our hospital. Of them, 36 were treated with ZOL and their OS was significantly better than that of the other 41 patients (1- and 3-year survival, 84% and 73% vs. 49% and 27%, respectively, p < 0.001). OS rates were clearly discriminated according to MSKCC model stratification: 3-year survival rates in the favorable, intermediate and poor risk groups were 83% (n = 12), 49% (n = 45), and 19% (n = 20), respectively (p=0.0033). To match characteristics in our retrospective study, we selected 45 patients conforming to MSKCC intermediate risk group criterion. In this cohort, 23 patients received ZOL (ZOL-treated group) whereas the other 22 did not (non-ZOL-treated group). The primary endpoint was OS and the secondary endpoint was the skeletal-related event (SRE) rate defined as the total number of SREs divided by the total years on study. Results: For the cohort of 45 patients, the median OS from diagnosis of bone metastases was 27.2 months. Multivariate analysis showed that low serum calcium (hazard ratio [HR]: 2.58, 95% confidence interval [CI]: 1.31 to 4.69; p = 0.0083) and ZOL treatment (HR: 1.89, 95% CI: 1.27 to 2.96; p = 0.0013) were independent factors predicting longer survival. The ZOL-treated group had significantly longer OS (1-year survival: 80.8%) than the non-ZOL-treated group (1-year survival: 59.1%, p = 0.0034). A difference in OS between the two groups still was present (p = 0.012) when the duration of molecular-targeted therapy was excluded from the OS period. Patients in the ZOL-treated group experienced a lower SRE rate (0.87/year) than patients in the non-ZOL-treated group (1.82/year, p = 0.0453). In particular, none of the patients in the ZOL-treated group developed spinal compression whereas 6 (28%) in the non-ZOL-treated group did (p = 0.0479). Conclusions: The current study indicates that ZOL not only reduces SREs but possibly improves OS in these patients.