Extension of a phase 3 trial of survival with atezolizumab plus chemotherapy for extensive-stage small cell lung cancer

The multinational phase 3 IMpower133 trial randomized patients with previously untreated extensive-stage small cell lung cancer (ES-SCLC) to atezolizumab plus chemotherapy for for cycles followed by atezolizumab maintenance every three weeks (n=201) or placebo plus chemotherapy for for cycles followed by placebo maintenance (n=201). The trial showed improved progression-free survival and overall survival in the atezolizumab group. At the closure of IMpower133, 18 out of 26 eligible patients from the atezolizumab group rolled over to the IMbrella A trial, and continued receiving atezolizumab every three weeks. The 3-, 4-, and 5-year overall survival estimates were 16% (95% CI 11-21), 13% (8-18), and 12% (7-17), respectively. Serious adverse events occurred in three patients (16.7%). The authors conclude that with a 5-year survival rate of 12%, addition of atezolizumab to first-line chemotherapy resulted in favorable outcomes when compared with historical data with chemotherapy alone.