The utilization of immunotherapy with radiation therapy in lung cancer: a narrative review

Despite decreasing smoking rates, lung cancer remains the leading cause of death from cancer in the United States. Radiation therapy has been established as an effective locoregional therapy for both early stage and locally advanced disease and is known to stimulate local immune response. Past treatment paradigms have established the role of combining cytotoxic chemotherapy regimens and radiation therapy to help address the local and systemic nature of lung cancer. However, these regimens have limitations in their tolerability due to toxicity. Additionally, cytotoxic chemotherapy has limited efficacy in preventing systemic spread of lung cancer. Newer systemic agents such as immune checkpoint inhibitors have shown improved survival in metastatic and locally advanced lung cancer and have the advantage of more limited toxicity profiles compared to cytotoxic chemotherapy. Furthermore, improved overall response rates and systemic tumor responses have been observed with the combination of radiation therapy and immunotherapy, leading to numerous active clinical trials evaluating the combination of immune checkpoint inhibition with radiotherapy. This comprehensive review discusses the current clinical data and ongoing studies evaluating the combination of radiation therapy and immunotherapy in both non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC).