Updated Overall Survival and PD-L1 Subgroup Analysis of Patients With Extensive-Stage SCLC Treated With Atezolizumab, Carboplatin, and Etoposide

鈥� An ASCO Reading Room selection

March 19, 2021

Stephen V. Liu, MD; Martin Reck, MD, PhD; Aaron S. Mansfield, MD; Tony Mok, MD; Arnaud Scherpereel, MD, PhD; Niels Reinmuth, MD, PhD; Marina Chiara Garassino, MD; Javier De Castro Carpeno, MD; Raffaele Califano, MD; Makoto Nishio, MD; Francisco Orlandi, MD; Jorge Alatorre-Alexander, MD; Ticiana Leal, MD; Ying Cheng, MD; Jong-Seok Lee, MD; Sivuonthanh Lam, PharmD; Mark McCleland, PhD; Yu Deng, PhD; See Phan, MD; and Leora Horn, MD

Journal of Clinical Oncology

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Purpose

IMpower133 (ClinicalTrials.gov identifier: ), a randomized, double-blind, phase I/III study, demonstrated that adding atezolizumab (anti-programmed death-ligand 1 [PD-L1]) to carboplatin plus etoposide (CP/ET) for first-line (1L) treatment of extensive-stage small-cell lung cancer (ES-SCLC) resulted in significant improvement in overall survival (OS) and progression-free survival (PFS) versus placebo plus CP/ET. Updated OS, disease progression patterns, safety, and exploratory biomarkers (PD-L1, blood-based tumor mutational burden [bTMB]) are reported.

Patients and Methods

Patients with untreated ES-SCLC were randomly assigned 1:1 to receive four 21-day cycles of CP (area under the curve 5 mg per mL/min intravenously [IV], day 1) plus ET (100 mg/m² IV, days 1-3) with atezolizumab (1,200 mg IV, day 1) or placebo, and then maintenance atezolizumab or placebo until unacceptable toxicity, disease progression, or loss of clinical benefit. Tumor specimens were collected; PD-L1 testing was not required for enrollment. The two primary end points, investigator-assessed PFS and OS, were statistically significant at the interim analysis. Updated OS and PFS and exploratory biomarker analyses were conducted.

Results

Patients received atezolizumab plus CP/ET (n = 201) or placebo plus CP/ET (n = 202). At the updated analysis, median follow-up for OS was 22.9 months; 302 deaths had occurred. Median OS was 12.3 and 10.3 months with atezolizumab plus CP/ET and placebo plus CP/ET, respectively (hazard ratio, 0.76; 95% CI, 0.60 to 0.95; descriptive P = 0.0154). At 18 months, 34.0% and 21.0% of patients were alive in atezolizumab plus CP/ET and placebo plus CP/ET arms, respectively. Patients derived benefit from the addition of atezolizumab, regardless of PD-L1 immunohistochemistry or bTMB status.

Conclusion

Adding atezolizumab to CP/ET as 1L treatment for ES-SCLC continued to demonstrate improved OS and a tolerable safety profile at the updated analysis, confirming the regimen as a new standard of care. Exploratory analyses demonstrated treatment benefit independent of biomarker status.

Read an interview about the study here and expert commentary about the clinical implications here.

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Updated Overall Survival and PD-L1 Subgroup Analysis of Patients With Extensive-Stage SCLC Treated With Atezolizumab, Carboplatin, and Etoposide

Primary Source

Journal of Clinical Oncology

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