Atezolizumab in combination with carboplatin and etoposide for heavily treated small cell lung cancer.

Atezolizumab was the first immune checkpoint inhibitor (ICI) to be introduced as a first-line treatment option for extensive-stage small cell lung cancer (ES-SCLC), in combination with carboplatin and etoposide (CE) chemotherapy. However, SCLC treatment options after progression to first-line chemotherapy are limited, warranting the readministration of previously used drugs. In combination with atezolizumab, CE readministration may theoretically be effective, based on two tentative mechanisms: its additive and synergistic effects on cytotoxic chemotherapy. The additive effect is based on the IFCT-1603 trial in which the Kaplan-Meier estimates of both progression-free survival (PFS) and overall survival (OS) in the atezolizumab group exhibited a tail plateau in the selected population. Conversely, an anti-PD-L1 antibody synergistic effect on platinum compounds was assessed in a preclinical study, which was reinforced by clinical data. Thus, atezolizumab in combination with CE may be a treatment option in heavily treated patients. Here, we describe the first case of a heavily treated ES-SCLC patient treated with chemoimmunotherapy, resulting in a partial response and a durable PFS. KEY POINTS: SIGNIFICANT FINDINGS OF THE STUDY AND WHAT THIS STUDY ADDS: CE readministration with atezolizumab may be effective based on two tentative mechanisms. Additive and synergistic effects of atezolizumab on CE have been previously suggested via a clinical trial and preclinical study, respectively. This is reflected in the current case in clinical settings.