Radiation and PD-1 inhibition: Favorable outcomes after brain-directed radiation

Abstract

Background and purpose: Patients with metastatic melanoma, renal cell carcinoma (RCC) and non-small cell lung cancer (NSCLC) are increasingly treated with immune checkpoint blockade targeting the programed death (PD)-1 receptor, often with palliative radiation therapy. Outcome data are limited in this population.

Material and methods: We retrospectively reviewed consecutive patients with metastatic NSCLC, melanoma, and RCC who received radiation and anti-PD-1 therapy at four centers.

Results: We identified 137 patients who received radiation and PD-1 inhibition. Median survival from first PD-1 therapy was 192, 394, and 121days for NSCLC, melanoma, and RCC patients. Among 59 patients who received radiation following the start of PD-1 blockade, 25 continued to receive PD-1 inhibition for a median of 179days and survived for a median of 238 additional days. Median survival following first course of radiation for brain metastases was 634days. Melanoma patients received brain directed radiation relatively less frequently following the start of PD-1 inhibitor treatment.

Conclusions: Incorporation of palliative radiation does not preclude favorable outcomes in patients treated with PD-1 inhibitors; patients irradiated after the start of PD-1 inhibition can remain on therapy and demonstrate prolonged survival. Of note, patients irradiated for brain metastases demonstrate favorable outcomes compared with historical controls.

Keywords: Immune checkpoint inhibitor; Immunotherapy; Radiation therapy.