Stereotactic body radiation therapy for curative treatment of adrenal metastases

The detection of oligometastatic adrenal metastases is increasing and there are limited data supporting the use of curative intent stereotactic body radiation therapy (SBRT) to treat patients with limited metastatic disease with adrenal involvement. Therefore, we utilized a prospectively maintained database of consecutive patients treated with SBRT for limited metastatic disease (≤5 sites) to identify patients with adrenal metastases. Patients were either treated on a three-fraction dose escalation protocol or a ten fraction off-protocol regimen. Outcomes including treated-metastasis control (TMC), distant control (DC), and overall survival (OS) were calculated by the Kaplan-Meier method. Ten patients with 13 adrenal metastases were identified for this case series. The median follow-up was 14.9 months. No patient experienced grade 3 toxicity. The most common grade 1-2 acute toxicities were fatigue (80%) and GI toxicity (40%). One patient experienced late grade 2 adrenal insufficiency. Overall, the 1-year TMC rate was 73%, DC was 30%, and OS was 90%. Three treated adrenal metastases progressed, all receiving the lowest BED10 (43.2 Gy), corresponding to 24 Gy in 3 fractions. After treatment of adrenal metastases with SBRT, the median time to salvage chemotherapy was 5.3 months (range 1.0-38.8 months) and 1-year freedom from salvage chemotherapy was 44%. These results suggest that SBRT to adrenal metastases was tolerated with low toxicity in limited metastatic patients and control rates are promising. This study supports the growing body of literature treating patients with adrenal metastases with SBRT.