SBRT as definitive treatment of adrenal gland metastases: a single center experience

Purpose or Objective: Adrenal gland metastases are a common problem in oncology, causing abdominal pain, nausea and vomiting, leading to patient discomfort. Classical treatment includes surgical resection or chemotherapy, being palliative conformal 3D Radiotherapy the only non-invasive local treatment available. Recently new definitive treatment modalities such as Radiofrequency ablation and SBRT have been developed with promising results. The aim of this study is to analyze the safety and efficacy of SBRT treatment for adrenal gland metastases. Material and Methods: From April 2008 to September 2018 a total of 32 selected patients have been treated of adrenal gland metastases with SBRT at our Institution. Treatment techniques included fiducial-based Adaptive Respiratory Gating (7 patients), Dampening (19) and Active Breathing Coordinator (6). Treatment planning included 7 patients with VMAT, 11 with 3D Conformal Radiotherapy and 6 with IMRT (Fig1). Toxicity was evaluated with CTCAE v5.0. Statistical analysis included descriptive tests and Kaplan Meier curves for survival. [Figure Presented] Results All patients (18 males and 14 females) completed treatment as scheduled. The most common location of the primary tumor was lung (75%). Other locations were: gynecological (6%), colorectal, melanoma and sarcoma (3% each). Sixteen patients received SBRT for right adrenal gland, 15 for left gland and 1 for both glands. Median dose of 47 Gy (range 24-60 Gy) and median dose/fraction of 12 Gy (range 5-20 Gy) was administered. The median PTV size and volume was 31 mm and 57 cc respectively. With a median follow up of 13.2 months local control crude rate was 88.89%. Five patients achieved a complete response, 11 partial response, 7 stable disease and 3 local progression. Estimated local control at 16 months was 77.3%. Median local failure free survival was not reached. Other distant metastases appeared in 85.2% of patients. Median overall survival was 12 months. Fifty seven percent of patients were alive at 12 months. As prognostic factors we found that left adrenal metastases had statistically significant worse local control than right adrenal ones, which is straightly related with the total dose administered. Doses with BED above 100 Gy (BED-α/β10) had statistically significant better local control than those treated with BED of 100 Gy or below (Fig2). Local control after SBRT was not related with overall survival. [Figure Presented] Tolerance to the procedure was generally good. Ten patients presented acute toxicity, being asthenia Grade 1 or 2 the most frequent in seven patients. Chronic toxicity was reported in two patients (6.25%), one Grade 3 enteritis and one Grade 3 abdominal abscess. No Grade 4-5 acute or chronic toxicity was reported. Conclusion: In our experience SBRT for adrenal gland metastases is safe and effective, achieving good local control rates, which are directly related with the total dose administered. Further studies are needed to consolidate these results and evaluate the influence of SBRT in patient survival and quality of life.