Role of radiotherapy in extracranial metastatic malignant melanoma in the modern era

BACKGROUND: To assess the role of radiotherapy in metastatic malignant melanoma (MM) patients in modern era. MATERIALS AND METHODS: This is a retrospective study of MM patients treated with radiotherapy at Mayo Clinic from 1999 to 2014. Patients with pre- and post-treatment imaging studies (CT, MRI, and/or PET/CT) were assessed for metastasis failure (MF), regional/distant failure, and overall survival (OS). RESULTS: In 75 MM patients, 56 and 68 lesions were treated with conventional/hypofractionated radiotherapy (CHRT) and stereotactic body radiotherapy (SBRT), respectively. The median doses for CHRT and SBRT were 30 Gy and 50 Gy, respectively. 1-year MF was 17% (SBRT 6% vs CHRT 31%, p < 0.01). 1-year regional (5% vs 29%, p < 0.01) and distant progression (75% vs 89%, p < 0.01) were improved with SBRT. Median OS was 15.6 months (CHRT 7.0 vs SBRT 22.9, p < 0.01). Prognostic factors for OS included age ≤55 years (RR 0.25), oligometastatic disease (RR 0.34), SBRT (RR 0.38) and treating all lesions (RR 0.28, all p < 0.01). CONCLUSIONS: SBRT for extracranial MM exhibited improved MF compared with CHRT, consistent with intracranial radiosurgery data. Though these data are retrospective and subject to selection bias, our findings support the prudent use of SBRT in a select group of favorable, oligometastatic MM patients, and should be discussed as an alternative to surgery and ablation.