Stereotactic Body Radiation Therapy for Oligometastatic Renal Cell Carcinoma or Melanoma: Prognostic Factors and Outcomes

Purpose/Objective(s): Renal cell carcinoma (RCC) and melanoma have classically been regarded as radioresistant tumors, requiring higher radiation doses per fraction to obtain a tumoricidal effect. Even with new targeted agents, outcomes have not dramatically improved with systemic therapies in the metastatic setting. Since oligometastatic disease carries a more favorable prognosis, we sought to characterize the outcomes and prognostic factors in patients treated with stereotactic body radiation therapy (SBRT). Materials/Methods: We retrospectively analyzed 31 consecutive patients with extracranial RCC or melanoma oligometastases treated at 1 institution with SBRT from January 2001 to December 2012. Survival was defined as time from completion of SBRT to last follow-up or death. Results: The median age of patients was 60.1 years (range 44.6e85.3 years), with 20 (64.5%) being male; 16 patients had RCC, and 15 had melanoma. Twenty-six percent of patients had brain metastases diagnosed prior to SBRT. The median number of treated metastases was 2 (range 1e5), treated a median of 40.9 months after diagnosis of the primary site. A total of 67 oligometastases were treated with SBRT; 63% and 21% of the lesions were located in the lung and liver, respectively. Median SBRT dose was 50 Gy, and median fractional dose was 5 Gy. Median gross tumor volume was 8.05 mL. Eighty-one percent had a KPS of 80 or higher at time of SBRT. Thirty-nine percent of patients received systemic therapy sometime after SBRT, and 39% had received subsequent radiation for additional metastases. The median overall survival (OS) and progression-free survival (PFS) was 10.8 and 4.0 months, respectively. Median OS and PFS were greater in patients with RCC (OS: 50.2 vs. 8.3 months, P<.001; PFS: 6.0 vs. 2.8 months, PZ.04). Local control rate of SBRT-treated lesions was excellent (1 year: 94.7%). Favorable prognostic factors for OS included higher SBRT total dose (HR [per Gy] 0.94, 95% CI: 0.90-0.99), higher KPS (HR [90-100 vs. 80] 0.34, 95% CI: 0.14-0.97), and absence of brain metastases prior to SBRT (HR 0.37, 95% CI: 0.15-0.90). Improved PFS was associated with male gender (HR 0.41, 95% CI: 018-0.97), no previous brain metastases (HR 0.39, 95% CI: 0.15-0.97), and better KPS (HR [90-100 vs. 80] 0.37, 95% CI: 0.14-0.97). Prior distant metastases, total number of SBRT-treated lesions, time from primary diagnosis to SBRT, SBRT dose and fraction size, and whether additional radiation or systemic therapy was administered any time after SBRT were not associated with OS or PFS. Conclusion: For patients with extracranial oligometastases from RCC or melanoma, SBRT results in excellent local control and may offer a survival benefit, especially in patients with good performance status and no prior brain metastases. This retrospective series supports larger trials using SBRT for treatment of these histologies. Author Disclosure: C.E. Grossman: None. P. Okunieff: None. R.A. Brasacchio: None. A.W. Katz: None. D.P. Singh: None. K.Y. Usuki: None. Y. Chen: None. M.T. Milano: None.