Single Institution Experience with Stereotactic Body Radiation Therapy for Treatment of Adrenal Gland Metastases

Abstract

The adrenal gland is a common site for metastatic spread from many types of cancer. A non-invasive ablative modality, stereotactic body radiotherapy (SBRT) has emerged as a promising alternative option for the local treatment of oligometastatic disease. Our purpose is to report our institutional experience of SBRT for adrenal metastases and assess its impact on renal function. Data was retrieved from patients who were diagnosed with adrenal metastases and treated with SBRT between 2008 and 2017. Patients with primary adrenal malignancies were excluded. Disease progression was analyzed by CT, using the Response Evaluation Criteria in Solid Tumors v1.1, and/or by FDG-PET/CT, using the PET Response Evaluation Criteria in Solid Tumors v1.0. Toxicities were graded according to the Common Terminology Criteria for Adverse Events v4.0. The estimated glomerular filtration rate (eGFR) nadir obtained between 3 and 6 months after SBRT was compared with baseline eGFR. Time-to-events were calculated from date of SBRT. In total, 35 patients with adrenal metastases were identified. Within this cohort, a total of 39 adrenal gland metastases were included for this analysis. Four patients were treated for bilateral disease. Most of the metastases originated from NSCLC (48%), followed by hepatocellular carcinoma (HCC) (20%) and other tumors of the gastrointestinal tract (9%). For 28 patients (80%), adrenal tumors were considered metachronous metastases. All tumors were FDG-avid on PET/CT, with a median tumor largest dimension of 2.9 cm (range: 0.7-9). The median dose was 40 Gy (range: 20-54) in 5 fractions (range: 1-6). The median follow-up was 37 months (range: 14-451) from disease diagnosis and 7 months (range: 1-54) from the SBRT start date. With death treated as a competing event, the cumulative incidence of local failure (LF) at 1-year after SBRT was of 7.6% and 19.2% at 3 years. Median overall survival (OS) was 19 months (95% CI: 8-54 months). Tumor size correlated with OS time (P = .0006). When dichotomized by the median size, patients with tumors < 2.9 cm had a median OS of 54 months, compared to 11 months for those with adrenal tumors ≥ 2.9 cm (P = .01). Similarly, GTV also correlated with OS (P = .001). Incidence of Grade 2 toxicity was of 17%, with no case of Grade ≥ 3 toxicity. SBRT did not impact renal function, with a mean eGFR decline of only 2.6 ± 8 mL/min/1.73 m2 compared to baseline. Combined kidneys V5 and combined renal cortex V17.5 did not correlate with eGFR change (P = .7 and P = .9, respectively). In summary, we demonstrated that treatment of adrenal metastases with SBRT is associated with excellent local control and very low toxicity rates. Furthermore, our analysis suggests that adrenal SBRT has minimal, if any significant impact on renal function. Further analysis of a larger patient population is needed in order to confirm these findings.