Clinical factors associated with durable response to atezolizumab in extensive-stage small-cell lung cancer: A real-world analysis in Moscow.

e20160 Background: Atezolizumab (A) in combination with platinum-etoposide chemotherapy represents the current standard of care for the first-line treatment of extensive-stage small-cell lung cancer (ES-SCLC). However, sustained clinical benefit is achieved only in a limited cohort of patients (pts). Identifying predictors of long-term response may optimize patient selection and improve understanding of immunotherapy outcomes in SCLC. Methods: This retrospective real-world study included 335 consecutive pts with ES-SCLC (stage III – 34 pts, stage IV – 301 pts) who received first-line treatment with atezolizumab in combination with platinum-etoposide chemotherapy. Long responders (LRs) were defined as pts achieving progression-free survival (PFS) 12 months or longer. Baseline demographic, clinical, radiological and laboratory characteristics were collected and compared between LRs and pts without durable response using chi-square tests with Yates correction and t-tests. Results: Seventy-five pts (22.4%) were classified as LRs. Median age in the overall cohort was 63 years (range 26–82), 61 years in LRs (range 36–82). In the entire population median PFS was 6.9 months (95% CI, 6.4–7.4), with a 1-year PFS rate of 26.4%; median overall survival (mOS) was 12.1 months (95% CI, 10.2–13.9), with a 1-year OS rate of 50.3%. LRs demonstrated a markebly prolonged OS compared with non–long responders (non-LRs): mOS 47.9 vs 8.6 months. 10 pts (13,3%) in LRs-group had st III disease. Favorable ECOG performance status (0–1) was more common among LRs (53.3% vs 35.8%, p = 0.013). Disease burden was higher in non-LRs group: liver metastases (40.0% vs 14.7%, p < 0.001), bone metastases (28.5% vs 14.7%, p = 0.023), and elevated lactate dehydrogenase (LDH) above the upper limit of normal (65.6% vs 34.3%, p < 0.01). No significant differences were observed between LRs and non-LRs in the incidence of brain metastases, age ≥65 years, gender, or laboratory parameters including transaminase elevation, serum calcium, C-reactive protein, and albumin levels. Conclusions: In this real-world ES-SCLC cohort, approximately one-fifth of pts achieved durable benefit from atezolizumab beyond 12 months. Favorable ECOG performance status (0–1) and non-elevated LDH may suggest a benefit from using atezolizumab with platinum-etoposide agents while other features (ECOG 2-3, liver and bone mts and elevated LDH) reflect aggressive disease biology and associates with lack of long-term response. These readily available clinical factors may help identify patients less likely to derive durable benefit from immunotherapy and warrant prospective validation.