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. Small‐cell lung cancer treatment options are scarce and limited, which sometimes leads to readministration of previously used drugs in heavily treated patients. Carboplatin and etoposide (CE) readministration with atezolizumab was effective in the current case, which may be based on two tentative mechanisms: additive and synergistic effects of atezolizumab on CE.