Abstract
BACKGROUND AND PURPOSE: Antibodies against programmed cell death protein 1 (PD-1) are standard treatments for advanced melanoma. Palliative radiation therapy (RT) is commonly administered for this disease. Safety and optimal timing for this combination for melanoma has not been established. MATERIALS AND METHODS: In this retrospective cohort study, records for melanoma patients who received anti-PD-1 therapy at Duke University or Emory University (1/1/2013-12/30/2015) were reviewed. Patients were categorized by receipt of RT and RT timing relative to anti-PD-1. RESULTS: 151 patients received anti-PD-1 therapy. Median follow-up was 12.9 months. Patients receiving RT (n = 85) had worse baseline prognostic factors than patients without RT (n = 66). One-year overall survival (OS) was lower for RT patients than patients without RT (66%, 95% CI: 55-77% vs 83%, 95% CI: 73-92%). One-year OS was 61% for patients receiving RT before anti-PD-1 (95% CI: 46-76%), 78% for RT during anti-PD-1 (95% CI: 60-95%), and 58% for RT after anti-PD-1 (95% CI: 26-89%). On Cox regression, OS for patients without RT did not differ significantly from patients receiving RT during anti-PD-1 (HR 1.07, 95% CI: 0.41-2.84) or RT before anti-PD-1 (HR 0.56, 95% CI: 0.21-1.45). RT and anti-PD-1 therapy administered within 6 weeks of each other was well tolerated. CONCLUSION: RT can be safely administered with anti-PD-1 therapy. Despite worse baseline prognostic characteristics for patients receiving RT, OS was similar for patients receiving concurrent RT with anti-PD-1 therapy compared to patients receiving anti-PD-1 therapy alone.