Outcomes of Chemoimmunotherapy Among Patients With Extensive-Stage Small Cell Lung Cancer According to Potential Clinical Trial Eligibility

IMPORTANCE: Chemoimmunotherapy is the standard first-line therapy for patients with extensive-stage small cell lung cancer (ES-SCLC). However, whether findings from pivotal trials can be extrapolated to the clinical practice setting remains unclear. OBJECTIVE: To compare treatment outcome gaps following first-line chemoimmunotherapy for patients with ES-SCLC between those who met and did not meet the eligibility criteria used in previous clinical trials. DESIGN, SETTING, AND PARTICIPANTS: A prospective cohort study was conducted from September 1, 2019, to September 30, 2020, at 32 hospitals in Japan, with at least 12 months of follow-up. Participants included consecutive patients with ES-SCLC who received carboplatin and etoposide with atezolizumab as first-line therapy. EXPOSURES: Patients who met eligibility criteria for pivotal phase 3 clinical trials were considered trial-eligible. MAIN OUTCOMES AND MEASURES: The primary outcome was 6-month progression-free survival. The secondary outcomes were differences in progression-free survival, overall survival, and safety according to whether key clinical trial eligibility criteria were met. RESULTS: A total of 207 patients were analyzed (median age, 72 years; range, 46-87 years; 170 [82%] were male). Sixty-four patients (31%) were older adults (age ≥75 years), and most (184 [89%]) had an Eastern Cooperative Oncology Group performance status of 0 or 1. There were 132 (64%) trial-eligible patients. The 6-month progression-free survival rate for all patients was 38.8% (95% CI, 32.4%-45.7%). The median progression-free survival was 5.1 months in trial-eligible patients and 4.7 months in trial-ineligible patients (hazard ratio, 0.72; 95% CI, 0.53-0.97; P = .03). The proportion of patients who achieved disease control was 93% (118 of 127) in trial-eligible patients and 77% (55 of 71) in trial-ineligible patients (P = .002). The median overall survival was 15.8 months in trial-eligible patients and 13.1 months in trial-ineligible patients (hazard ratio, 0.73; 95% CI, 0.51-1.07; P = .10). The rate of severe adverse events was numerically higher among trial-ineligible patients than among trial-eligible patients (39% vs 27%; P = .07). CONCLUSIONS AND RELEVANCE: In this cohort study, the overall treatment outcome was comparable to that reported in pivotal clinical trials. However, treatment outcomes after chemoimmunotherapy might differ between trial-eligible and trial-ineligible patients. These findings suggest that trial-eligibility criteria may be useful in clinical practice, and further studies using data from clinical practice settings are required to inform regulatory approval and clinical decision-making.