Dramatic Response to Concurrent Anti-PD-1 Therapy and Radiation in Resistant Tumors with Sarcomatoid Differentiation.

A substantial fraction of patients demonstrate resistance to immune checkpoint inhibitors, which limits their use. Use of radiation concurrently with checkpoint inhibitors has been shown to boost immune responsiveness, resulting in significant tumor regression in patients with metastatic melanoma. However, it is unknown whether radiation could play a role in reversing the inherent resistance to checkpoint inhibition in certain tumor types. Most trials testing this concurrent approach exclude such modestly responsive tumors and pursue checkpoint inhibition using anti-cytotoxic T-lymphocyte-associated protein 4 antibody (anti-CTLA-4, ipilimumab). The efficacy of anti-programmed-death-1 (anti-PD-1) therapy when used concurrently with radiation is less known but remains an attractive option due to less autoimmune toxicity compared with CTLA-4 inhibition. In this first reported experience, we have safely and effectively combined anti-PD-1 therapy (nivolumab) concurrently with radiation to treat two patients with relapsed sarcomatoid renal carcinoma and heavily pretreated pleomorphic sarcoma. Both patients experienced a dramatic response that was durable.