Atezolizumab Plus Chemotherapy in Previously Untreated Extensive-Stage Small Cell Lung Cancer

Key Points

  • The addition of atezolizumab to platinum-based chemotherapy increased overall survival.
  • Progression-free survival was also significantly improved.

As reported at the recent International Association for the Study of Lung Cancer 19th World Conference on Lung Cancer and in The New England Journal of Medicine by Horn et al, the phase III IMpower133 study has shown significant improvement in overall and progression-free survival with the addition of atezolizumab (Tecentriq) to platinum-based chemotherapy in the first-line treatment of extensive-stage small cell lung cancer.

In the double-blind trial, 403 patients from 106 sites in 21 countries were randomly assigned between June 2016 and May 2017 to receive atezolizumab at 1,200 mg (n = 201) or placebo (n = 202) on day 1 of each 21-day cycle plus carboplatin (AUC = 5 on day 1) and etoposide (100 mg/m2 on days 1 to 3) for 4 cycles. Patients then received either atezolizumab or placebo until disease progression per Response Evaluation Criteria in Solid Tumors or unacceptable toxicity. The primary endpoints were investigator-assessed progression-free and overall survival.

Survival and Adverse Events

Median follow-up was 13.9 months. Median overall survival was 12.3 months in the atezolizumab group vs 10.3 months in the placebo group (hazard ratio [HR] = 0.70, P = .007). Overall survival at 1 year was 51.7% vs 38.2%. Hazard ratios for overall survival favored atezolizumab among nearly all subgroups examined. Median progression-free survival was 5.2 months vs 4.3 months (HR = 0.77, P = .02).

Grade 3 or 4 adverse events occurred in 56.6% of the atezolizumab group vs 56.1% of the placebo group, with the most common in both groups being neutropenia, anemia, and decreased neutrophil count. Death considered related to treatment occurred in 3 patients (1.5%) in each group. Potential immune-related adverse events occurred in 39.9% vs 24.5% of patients, with rash and hypothyroidism being the most common in the atezolizumab group.

The investigators concluded, “The addition of atezolizumab to chemotherapy in the first-line treatment of extensive-stage small cell lung cancer resulted in significantly longer overall survival and progression-free survival than chemotherapy alone.”

The study was funded by F. Hoffmann–La Roche/Genentech.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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