Pembrolizumab Offers New Option in Extensive-Stage Lung Cancer

A pooled analysis of two trials found that pembrolizumab results in durable responses and promising overall and progression-free survival in patients with heavily pretreated extensive-stage small-cell lung cancer (SCLC). This could represent a new treatment option in a difficult-to-treat patient population.

“Outcomes are very poor in patients who experience disease progression after first- and second-line therapy for extensive-stage SCLC,” said Hyun Cheol Chung, MD, PhD, of the Yonsei Cancer Center at the Yonsei University College of Medicine in Seoul. He presented results of a pooled analysis of the KEYNOTE-028 and KEYNOTE-158 trials at the American Association for Cancer Research (AACR) Annual Meeting, held March 29–April 3 in Atlanta (abstract CT073).

Of 131 patients included in those two studies, 83 patients had received at least 2 prior lines of therapy and were included in the new analysis. They were followed for a median of 7.7 months; the median age was 62 years, and 64% of the cohort was male. Most patients (64%) had received 2 prior lines of therapy, while 36% had received 3 or more lines.

A total of 16 patients (19.3%) responded to pembrolizumab; 14 of these 16 patients were programmed death ligand 1 (PD-L1) positive. There were 2 complete responses and 14 partial responses, and another 15 patients (18%) had stable disease; 45 patients (54%) had progressive disease. The responses were durable, with a median duration of response that was not yet reached; 9 patients (61% of responders) had a duration of response of at least 18 months.

The median progression-free survival (PFS) was 2.0 months. At 6 months, the PFS rate was 26.5%, and at 12 months it was 16.9%; at 24 months, the PFS rate was 13.1%. The median overall survival (OS) was 7.7 months, and the OS rates at 6, 12, and 24 months were 56.3%, 34.3%, and 20.7%, respectively.

A total of 51 patients (61%) had a treatment-related adverse event (AE) of any grade, and 7% had a grade 3 AE. There were 2 grade 5 treatment-related AEs, including pneumonia and intestinal ischemia. The AE rates were similar to that seen in patients in these trials who received one or more prior lines of therapy.

“This pooled analysis supports the use of pembrolizumab monotherapy for patients with extensive-stage SCLC as third-line or later therapy,” Chung said.

Louis M. Weiner, MD, of the Georgetown Comprehensive Cancer Center at Georgetown University, who was not involved with the study, stressed the importance of these results. “To put this in perspective, SCLC that is extensive and is multiply relapsed is a disease setting where responses are rare, long-term survival is unheard of, and duration of response can be measured almost in minutes as opposed to in months,” he said during a press conference at the AACR meeting. “These findings are really stunning to anyone who has been in the field for awhile. ... This is an important advance.”