For patients with extensive-stage small-cell lung cancer, adding the anti–CTLA-4 antibody ipilimumab (Yervoy) to etoposide and platinum did not improve overall survival, compared with administering etoposide and platinum alone, investigators reported in the Journal of Clinical Oncology.

“Although exploratory in nature, chemotherapy plus ipilimumab did not demonstrate significant improvement in other endpoints, and no subgroups demonstrated greater benefit versus chemotherapy alone,” added Martin Reck, MD, of LungenClinic Grosshansdorf (Germany), and his associates.

The randomized phase III study enrolled 1,132 chemotherapy-naive patients who were randomly assigned to either chemotherapy plus ipilimumab (etoposide plus investigator’s choice of cisplatin or carboplatin during cycles one to four, and ipilimumab during cycles three to six) or to chemotherapy plus placebo (etoposide plus investigator’s choice of cisplatin or carboplatin during cycles one to four, and placebo during cycles three to six). Patients with a complete or partial response during induction could undergo prophylactic cranial irradiation before starting maintenance ipilimumab (10 mg/kg) or placebo administered every 12 weeks, the investigators reported (J Clin Oncol. 2016 July 26. doi:10.1200/JCO.2016.67.6601).

Among 954 patients who received at least one dose of study therapy, the primary endpoint, median overall survival, was 11.0 months for the ipilimumab-chemotherapy arm and 10.9 months for the placebo arm (hazard ratio, 0.9; 95% confidence interval, 0.8-1.1; P = .4). “Across most prespecified patient subgroups, hazard ratios for overall survival [also] did not seem to favor one treatment arm,” the researchers wrote.

Ipilimumab also failed to achieve a meaningful increase in median progression-free survival, compared with placebo (4.6 months and 4.4 months, respectively). There was only one complete response in the ipilimumab-chemotherapy group and none in the chemotherapy-placebo group. A total of 62% of patients achieved a partial response in each group, and the median duration of response was 4 months in the ipilimumab-chemotherapy group (95% CI, 3.3-4.2 months) versus 3.5 months (95% CI, 3.3-4.1 months) in the chemotherapy-placebo group.

There were no new or unexpected safety signals, but ipilimumab was associated with higher rates of overall and severe-grade diarrhea, colitis, and rash. The five treatment-related deaths in the ipilimumab-chemotherapy group included two from colitis, two from sepsis, and one from liver toxicity. “In the chemotherapy plus placebo arm, there were two treatment-related deaths, one resulting from sepsis and one from bone marrow suppression,” the researchers wrote. Treatment-related discontinuations also were more common with ipilimumab plus chemotherapy (18%) than with chemotherapy plus placebo (2%).

“To date, PD-1 inhibitors, alone or in combination with CTLA-4 inhibitors, show the most promise in small-cell lung cancer,” the investigators said. Multiple trials are exploring the use of these agents as maintenance therapy or in second-line settings, they added.

Bristol-Myers Squibb makes ipilimumab, funded the study, and helped collect and analyze the data. Dr. Reck disclosed financial ties to Bristol-Myers Squibb, Hoffmann-La Roche, Eli Lilly, Merck Sharp & Dohme, and several other pharmaceutical companies.