Dr. Horn on Updated IMpower133 Data in Small Cell Lung Cancer

Leora Horn, MD, MSc, Ingram Associate Professor of Cancer Research; associate professor of medicine (Hematology and Oncology); assistant director of the Educator Development Program and clinical director of the Thoracic Oncology Program at Vanderbilt-Ingram Cancer Center, discusses data from an updated analysis of the phase 3 IMpower133 trial, which examined the first-line combination of atezolizumab (Tecentriq), carboplatin, and etoposide in small cell lung cancer (SCLC).

Results from an exploratory analysis of IMpower133 presented during the 2020 AACR Virtual Annual Meeting showed that the combination continued to improve overall survival (OS) compared with chemotherapy alone in the frontline treatment of patients with extensive-stage SCLC, regardless of PD-L1 and blood tumor mutational burden (TMB) status.

One important thing to remember withseveral trials evaluating checkpoint inhibitors, Horn notes, is that oftentimes investigators are focusing on the tail of the curve and trying to understand whether patients are experiencing long-term survival. With longer follow-up, results showed that the triplet regimen continued to have an OS benefit, at 12.3 months with a hazard ratio of 0.76. Additionally, the 18-month OS was found to be 13% higher in patients treated with the triplet versus those given chemotherapy alone, at 34% versus 21%.

Updated results related to PD-L1 expression and TMBand and how these factors might help to predict outcomes with checkpoint inhibitor therapies were also presented. In the original publication, investigators examined blood TMB using cutoffs of both 10 and 16 and found that this factor did not serve as a predictor of response or survival with checkpoint inhibitor therapy. A benefit was observed in patients with high TMB and low TMB, Horn concludes.