Impact of underrepresented populations on clinical outcomes of chemo-immunotherapy for extensive-stage small cell lung cancer: Real-world prospective cohort study.

Abstract

8567 Background: Chemo-immunotherapy is the standard 1st-line therapy for patients with extensive-stage small cell lung cancer (ES-SCLC). Prospective data about underrepresented populations outside the clinical trial such as elderly or poor risk has not been revealed. Methods: We conducted a 32-hospitals prospective cohort study of consecutive patients with ES-SCLC who received carboplatin and etoposide with atezolizumab as 1st-line therapy between September 2019 and September 2020. The primary outcome was 6-months progression-free survival (PFS) probability of all patients. The secondary outcomes were overall survival (OS), PFS, time to treatment failure, objective response rate, safety, and differences in efficacy and safety depending on whether or not the key eligible study criteria of previous trials are met. Results: In total, 207 patients with ES-SCLC were analyzed. The median age was 72 years, and 64 patients (31%) were elderly (≥75 years). Most patients (89%) had a performance status (PS) of 0 or 1. As a result, 132 (64%) was categorized as eligible patients. The 6-months PFS probability of all patients was 38.8 % (95%CI:32.4-45.7%). Between eligible and ineligible patients, there was significant difference of patients who attained disease control (93% versus 77%, p = 0.002). Median PFS was significantly longer in eligible patients than ineligible patients (5.1 vs. 4.7 months; P =.03, HR 0.72 (95% CI 0.53–0.97)), and median OS was longer in eligible patients than ineligible patients, without any significant difference (15.8 vs. 13.1 months; P =.10, HR 0.73 (95% CI 0.51–1.07)). Survival analysis identified a PS score of 0-1 (HR: 0.60, 95% CI: 0.39-0.97, p = 0.03) as a significant predictor of better PFS, while PS score of 0-1 (HR: 0.51, 95% CI: 0.31-0.89, p = 0.01) and younger patients ( < 75 years) (HR: 0.66, 95% CI: 0.45-0.97, p = 0.03) as significant-good predictor of OS. The rate of severe AEs was higher in ineligible patients than in eligible (39% vs. 27%, respectively; p = 0.07), although the difference was not significant. Older age was significantly associated with severe AEs (p = 0.049). Conclusions: The real-world efficacy of chemo-immunotherapy for ES-SCLC was similar to that of pivotal clinical trials. However, trial-ineligible patients with ES-SCLC had poor treatment outcome and the higher rates of severe adverse events in this prospective cohort study. Our study suggests that positive results among the trial eligible patients may not translate to ineligible patients. Clinical trial information: UMIN000038064.