Effectiveness of Atezolizumab in Addition to Chemotherapy in ES-SCLC: A Retrospective Real-World Monocentric Study

<i>Background</i>: Small cell lung cancer (SCLC) is a malignant carcinoma characterized by high proliferative rate and early metastatization with limited treatment options and poor prognosis. The approval of ICIs has established a new standard of care for extensive-stage (ES)-SCLC (5). Atezolizumab, an anti PD-L1 monoclonal antibody, has been the first immune checkpoint inhibitor (ICI) to be approved for SCLC patients. This study aims to retrospectively evaluate the real-world effectiveness and safety of atezolizumab in a cohort of patients with ES-SCLC. <i>Methods</i>: We conducted a monocentric retrospective analysis of SCLC patients who received atezolizumab in addition to chemotherapy, between January 2020 and December 2023. Study design endpoints included progression-free survival (PFS), overall survival (OS), and adverse events. <i>Results</i>: A total of 134 patients were included in this study. Out of 134 patients who began the CEA protocol, 100 continued maintenance. Currently, 25 are alive, 17 still on atezolizumab, 5 on second-line therapy, and 3 receiving best supportive care. The median age was 65 years. Patients received a median of four cycles of CEA (range 1-6 cycles), while the median number of atezolizumab maintenance cycles was eight (range 0-75). The overall median survival was 15 months, with patients who received more than 30 cycles of atezolizumab showing OS of 46.7% at 48 months. Common adverse events included skin disorders, pneumonitis, colitis, alanine, and aspartate deaminase increment, dysthyroidism, and blood disorders with only 3% of patients experiencing grade 3 or higher toxicities. <i>Conclusions</i>: In this real-world cohort, atezolizumab demonstrated comparable effectiveness to clinical trial results, with a manageable safety profile. These findings support the use of atezolizumab as a viable treatment option for ES-SCLC in routine clinical practice.