The outcomes of atezolizumab therapy in combination with carboplatin and etoposide for small-cell lung cancer.

e20115 Background: Nearly two-thirds of patients with small-cell lung cancer (SCLC) are diagnosed at an advanced stage, associated with a poor prognosis and extremely low 5-year survival. Platinum-based chemotherapy with etoposide remains the standard treatment for such patients. In recent years, immune checkpoint inhibitors have shown improved outcomes for patients with advanced-stage SCLC. In Uzbekistan, there is currently insufficient research on atezolizumab for this oncological condition. Methods: The retrospective study included 34 patients with previously untreated stage IV SCLC and distant metastases in the central nervous system, lungs, lymph nodes, and liver. The patients underwent treatment from July 2022 to October 2023. The average age of the patients was 67.4±8.2 years, with 21 (61.8%) males and 13 (38.2%) females. The patients were divided into two groups: The 1st group comprised 14 (41.2%) individuals who received four 21-day cycles of carboplatin (AUC 5 mg/mL/min intravenously on day 1) + etoposide (100 mg/m² intravenously on days 1-3) + atezolizumab (1200 mg intravenously on day 1). Subsequently, they underwent maintenance therapy with atezolizumab until unacceptable toxicity or disease progression. The 2nd group consisted of 20 (58.8%) patients who underwent standard platinum-based chemotherapy (carboplatin + etoposide) following the same regimens. Immunohistochemical analysis was conducted using the Ventana BenchMark Ultra automatic stainer with Ventana PD-L1 SP263 monoclonal antibodies. Results: The median overall survival (OS) in the 1st patient group was 11.2 months (95% CI: 9.4-12.6), while in the 2nd group, it was 9.7 months (95% CI: 8.3-11.6). The median progression-free survival (PFS) in the 1st group was 4.8 months (95% CI: 3.9-5.3), and in the 2nd group, it was 4.1 months (95% CI: 3.1-4.6). The objective response rate in the 1st group was 41.2%, and in the 2nd group, it was 37.5%. An analysis of PD-L1 expression was conducted on both tumor cells (TC) and infiltrating immune cells (IC). The prevalence of PD-L1 expression ≥1% on TC or IC was 48.3%, while the prevalence of PD-L1 expression ≥5% was 17.4%. Among 5 patients in the 1st group with tumors showing PD-L1 expression ≥5% on TC or IC, the median OS was 15.6 months (95% CI: 11.2-17.1), compared to 8.4 months (95% CI: 7.3-9.6) in 8 patients in the 2nd group with a similar level of PD-L1 expression. The use of atezolizumab did not impact the toxicity of the administered chemotherapy. Conclusions: Adding atezolizumab to standard platinum-based chemotherapy in the first-line treatment of metastatic SCLC improves both OS and PFS in patients without increasing the toxicity of the treatment. The therapeutic benefit of atezolizumab is more pronounced in patients with elevated PD-L1 expression in tumor tissue.