Radiotherapy combined with zoledronate can reduce skeletal-related events in renal cell carcinoma patients with bone metastasis.

BACKGROUND: Skeletal-related events (SRE) are common in patients with renal cell carcinoma (RCC) that includes bone metastasis. The purpose of this study was to clarify the effectiveness of zoledronate with and without sunitinib, combined with radiotherapy, for the treatment of bone metastasis from RCC. METHODS: We retrospectively analyzed 62 RCC patients with bone metastasis, who had been treated with radiotherapy at our institution. We divided the study cohort into two groups: patients treated with radiotherapy alone (RT; n = 27) and those treated with radiotherapy combined with zoledronate (RT + Z; n = 35). We investigated the overall survival and post-irradiation (PI)-SRE-free rate for each group, as well as the effect of sunitinib in the RT + Z treatment group. In addition, we determined treatment effectiveness by imaging assessments and relative response rates. RESULTS: There was no significant difference in the survival rates between the RT and RT + Z treatment groups (p = 0.11). However, the PI-SRE-free rate in the RT + Z group was significantly higher than that in the RT group (p = 0.02). The PI-SRE-free rate was significantly higher in patients who were treated with sunitinib after radiotherapy than in those who were treated without sunitinib (p = 0.03). However, there was no significant difference in the relative response rates, as assessed by imaging, in each group. CONCLUSION: Radiotherapy combined with zoledronate is an effective treatment for RCC with bone metastasis to prevent PI-SRE. Sunitinib may reduce PI-SRE if used after radiotherapy and combined with zoledronate.