Thoracic radiotherapy for renal cell carcinoma metastases.

Abstract

409 Background: For patients with metastatic renal cell carcinoma (RCC), metastasis-directed local therapies can delay progression and need to initiate/switch systemic therapy. We examined our experience treating lung or mediastinal metastases from RCC with radiotherapy (RT). Methods: We reviewed patients with lung or mediastinal metastases from RCC treated with RT. Overall survival (OS) and local control (LC) was measured from the start of RT using the Kaplan-Meier method. Results: Seventy-one patients were treated with RT for 89 lung or mediastinal metastases. Median follow-up was 2.0 years (range 0.02-11.4 years) after RT for surviving patients. Most patients were male (n=53, 74.6%). Median age was 58.4 years at initial diagnosis. Histology was most frequently clear cell carcinoma (n=62, 89.9%). At the time of treatment, 18 patients (25.4%) had 1-3 metastases, and the remainder (74.6%) had 4 or more metastases. Forty-one patients (57.5%) received systemic therapy prior to thoracic radiation. Initial systemic therapy was most commonly sunitinib (45%) or pazopanib (32.5%). Median time from starting systemic therapy to initiation of radiation was 2.0 years. Fifty-eight lung metastases and 31 mediastinal metastases were treated with a median 5 fractions (range 1-40), to a median total dose of 4800 cGy (range 400-7000), with a median fraction size of 500 cGy (range 150-2000). Thirty-three lesions were treated with concurrent systemic therapy, which was most commonly nivolumab (n=16). Of 89 treated lesions, 11 (12%) had local tumor recurrence, at a median of 1.6 years (range 0.4-2.9 years) after initiation of radiation. 1, 3, and 5 year MC (metastasis control) were 96.6%, 83.5% and 67.9%, respectively. Nine patients were treated with radiation in order to delay initiation of systemic therapy. Of these, 3 eventually received systemic therapy, initiated at a median 2.5 years after radiation. At last follow-up, 41 patients (57.7%) had died. Median OS was 2.6 years. Survival at 1, 3, and 5 years was 65.2%, 48.5%, and 38%, respectively. Conclusions: Radiation achieves high metastasis control rates for lung and mediastinal metastases from RCC, potentially delaying the need for systemic therapy.