PD-1 checkpoint blockade alone or combined PD-1 and CTLA-4 blockade as immunotherapy for lung cancer?

INTRODUCTION: Signaling through T-cell surface, an immune checkpoint protein such as PD-1 or CTLA-4 helps dampen or terminate unwanted immune responses. Blocking a single immune checkpoint or multiple checkpoints simultaneously can generate anti-tumor activity against a variety of cancers including lung cancer. Area covered: This review highlights the results of recent clinical studies of single or combination checkpoint inhibitor immunotherapy in non-small cell lung cancer (NSCLC) or small cell lung cancer (SCLC). The authors discuss pembrolizumab and pembrolizumab plus ipilimumab, durvalumab and durvalumab plus tremelimumab, nivolumab and nivolumab plus ipilimumab for NSCLC as well as nivolumab and nivolumab plus ipilimumab for SCLC. Expert opinion: Available data suggest that, in both metastatic NSCLC and SCLC, combined PD-1 and CTLA-4 blockade may produce a higher tumor response rate than PD-1 blockade alone. Nevertheless, combination therapy is associated with an increased toxicity. Several larger-scale studies are currently ongoing. For checkpoint inhibitor immunotherapy in SCLC and NSCLC, combination therapy is associated with a higher incidence of toxicities than single therapy; however, it appears to help increase tumor response rate. The increased response rate, if confirmed in larger scale studies, will likely make combination therapy another useful therapeutic approach for lung cancer.