On March 18, 2019, the U.S. Food and Drug Administration (FDA) approved atezolizumab (Tecentriq) in combination with carboplatin and etoposide for the first-line treatment of adult patients with extensive-stage small cell lung cancer. Approval was based on the IMpower133 study (ClinicalTrials.gov identifier NCT02763579), a randomized (1:1), multicenter, double-blind, placebo-controlled trial in 403 patients with extensive-stage small cell lung cancer who received no prior chemotherapy for extensive-stage disease and had an Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1.
IMpower133 Details
In the IMpower133 trial, patients were randomly assigned to one of the following regimens:
- Atezolizumab at 1,200 mg and carboplatin AUC 5 mg/mL/min on day 1 and etoposide at 100 mg/m2 intravenously on days 1, 2, and 3 of each 21-day cycle for a maximum of 4 cycles, followed by atezolizumab at 1,200 mg once every 3 weeks until disease progression or unacceptable toxicity
- Placebo and carboplatin AUC 5 mg/mL/min on day 1 and etoposide at 100 mg/m2 intravenously on days 1, 2, and 3 of each 21-day cycle for a maximum of 4 cycles, followed by placebo once every 3 weeks until disease progression or unacceptable toxicity.
Major efficacy outcome measures were overall and progression-free survival, as assessed by investigator per Response Evaluation Criteria in Solid Tumors v1.1 in the intent-to-treat population. The median overall survival was 12.3 months (10.8–15.9 months) for patients receiving atezolizumab with chemotherapy and 10.3 months (9.3–11.3 months) for those receiving placebo with chemotherapy (hazard ratio [HR] = 0.70; 95% confidence interval [CI] = 0.54–0.91; P = .0069). The median progression-free survival was 5.2 months (4.4–5.6 months) compared with 4.3 months (4.2–4.5 months) in the atezolizumab and placebo arms, respectively (HR = 0.77; CI = 0.62–0.96; P = .0170).
Fatigue/asthenia, nausea, alopecia, constipation, and decreased appetite were the most common adverse reactions in the study population. The recommended atezolizumab dose is 1,200 mg intravenously over 60 minutes every 3 weeks. ■
