Atezolizumab + Carboplatin/Etoposide for Extensive-Stage Small Cell Lung Cancer: IMpower133 Update
- 3 years ago
As reported in the Journal of Clinical Oncology by Stephen V. Liu, MD, and colleagues, an updated overall survival analysis in the phase I/III IMpower133 trial showed continued benefit with the addition of atezolizumab to carboplatin/etoposide as first-line treatment in patients with extensive-stage small cell lung cancer (SCLC). A benefit with atezolizumab was observed irrespective of PD-L1 or blood-based tumor mutational burden status.
The primary analysis of the trial showed improved progression-free and overall survival with the addition of atezolizumab, and supported the March 2019 approval of the agent in combination with carboplatin/etoposide in first-line treatment of adult patients with extensive-stage SCLC. At primary analysis, with a median follow-up of 13.9 months, median overall survival was 12.3 months in the atezolizumab group vs 10.3 months in the carboplatin/etoposide group (hazard ratio [HR] = 0.70, P = .007) and median progression-free survival was 5.2 months vs 4.3 months (HR = 0.77, P = .02).
Study Details
In the double-blind trial, 403 patients were randomly assigned to receive atezolizumab plus carboplatin/etoposide (n = 201) or placebo plus carboplatin/etoposide (control group, n = 202). Treatment consisted of four 21-day cycles of carboplatin (AUC = 5 mg per mL/min on day 1) plus etoposide (100 mg/m2 on days 1–3) plus either atezolizumab (1,200 mg on day 1) or placebo, with maintenance atezolizumab or placebo continued until disease progression, unacceptable toxicity, or loss of clinical benefit. PD-L1 testing was not required for enrollment. The two primary endpoints were investigator-assessed progression-free survival and overall survival.
Key Findings
At data cutoff for the preplanned updated analysis (January 2019), follow-up had continued for an additional 9 months. Median follow-up was 23.1 months in the atezolizumab group and 22.6 months in the control group.
At the updated overall survival analysis, median overall survival was 12.3 months (95% confidence interval [CI] = 10.8–15.8 months) in the atezolizumab group vs 10.3 months (95% CI = 9.3–11.3 months) in the control group (HR = 0.76, 95% CI = 0.60–0.95, descriptive P = .0154), with 12- and 18-month rates of 51.9% vs 39.0% and 34.0% vs 21.0%.
At updated analysis, median-progression-free survival was 5.2 months vs 4.3 months (HR = 0.77, 95% CI = 0.63–0.95). Updated response analysis showed confirmed objective response rates of 60.2% vs 64.4% (descriptive P = .3839). Median duration of response was 4.2 months vs 3.9 months (HR = 0.67, 95% CI = 0.51–0.88).
Among 137 patients with available PD-L1 status, median overall survival among those with PD-L1 expression on tumor cells or tumor-infiltrating immune cells
The primary analysis of the trial showed improved progression-free and overall survival with the addition of atezolizumab, and supported the March 2019 approval of the agent in combination with carboplatin/etoposide in first-line treatment of adult patients with extensive-stage SCLC. At primary analysis, with a median follow-up of 13.9 months, median overall survival was 12.3 months in the atezolizumab group vs 10.3 months in the carboplatin/etoposide group (hazard ratio [HR] = 0.70, P = .007) and median progression-free survival was 5.2 months vs 4.3 months (HR = 0.77, P = .02).
Study Details
In the double-blind trial, 403 patients were randomly assigned to receive atezolizumab plus carboplatin/etoposide (n = 201) or placebo plus carboplatin/etoposide (control group, n = 202). Treatment consisted of four 21-day cycles of carboplatin (AUC = 5 mg per mL/min on day 1) plus etoposide (100 mg/m2 on days 1–3) plus either atezolizumab (1,200 mg on day 1) or placebo, with maintenance atezolizumab or placebo continued until disease progression, unacceptable toxicity, or loss of clinical benefit. PD-L1 testing was not required for enrollment. The two primary endpoints were investigator-assessed progression-free survival and overall survival.
Key Findings
At data cutoff for the preplanned updated analysis (January 2019), follow-up had continued for an additional 9 months. Median follow-up was 23.1 months in the atezolizumab group and 22.6 months in the control group.
At the updated overall survival analysis, median overall survival was 12.3 months (95% confidence interval [CI] = 10.8–15.8 months) in the atezolizumab group vs 10.3 months (95% CI = 9.3–11.3 months) in the control group (HR = 0.76, 95% CI = 0.60–0.95, descriptive P = .0154), with 12- and 18-month rates of 51.9% vs 39.0% and 34.0% vs 21.0%.
At updated analysis, median-progression-free survival was 5.2 months vs 4.3 months (HR = 0.77, 95% CI = 0.63–0.95). Updated response analysis showed confirmed objective response rates of 60.2% vs 64.4% (descriptive P = .3839). Median duration of response was 4.2 months vs 3.9 months (HR = 0.67, 95% CI = 0.51–0.88).
Among 137 patients with available PD-L1 status, median overall survival among those with PD-L1 expression on tumor cells or tumor-infiltrating immune cells