Radiotherapy and Immunotherapy Combinations for Lung Cancer.

PURPOSE OF REVIEW: Positive results from recent immunotherapy trials of non-small cell lung cancer (NSCLC) have coincided with a greater appreciation for the impact of radiation therapy (RT) on tumor immunity. Here, we summarize key clinical findings and ongoing efforts to combine immunotherapy and RT for the treatment of NSCLC. RECENT FINDINGS: The role of immunotherapy for NSCLC has expanded significantly following the pivotal approvals of nivolumab and pembrolizumab for metastatic NSCLC, maintenance durvalumab in unresectable stage III NSCLC, and atezolizumab for metastatic NSCLC. Several small early-phase trials have demonstrated the ability of RT to elicit clinically significant tumor immunity. These positive findings support current trial efforts combining RT with immunotherapy for NSCLC. Recently initiated trials of RT and immunotherapy hold significant promise in expanding the therapeutic options for NSCLC. Optimization of therapy will require careful patient selection to yield meaningful improvements in clinical outcomes.

Generating antitumor immunity by targeted radiation therapy: Role of dose and fractionation.

Accumulating evidence supports the role of radiation therapy in the induction of antitumor immunity. With recent advancements in stereotactic radiation therapy, there is increasing appreciation that, when combined with immune checkpoint blockade, the type of radiation dose and fractionation regimen selected may both influence local tumor control and also affect the generation of immune responses that are important for systemic control. Although a broad range of radiation dose and fractionation schema have been tested in both the preclinical and clinical settings, recent preclinical evidence suggests the existence of a dose per fraction threshold beyond which radiation becomes less effective in generating tumor immune responses. Such a threshold seems to be tumor dependent, probably reflecting different genetic mutations of cancer. In this review we discuss the key preclinical and clinical evidence relating to radiation dose and fractionation considerations. Future clinical trials should focus on identifying optimal radiation dose and fractionation schedules, which may depend on the clinical context.