medwireNews: Single-agent pembrolizumab could be a promising option for extensive-stage small-cell lung cancer (SCLC) patients who have received at least two prior lines of therapy, suggests a pooled analysis of data from the multicohort KEYNOTE-028 and -158 trials.
Hyun Cheol Chung (Yonsei University College of Medicine, Seoul, South Korea), who presented the findings at the AACR Annual Meeting 2019 in Atlanta, Georgia, USA, told the press: “Our study shows that pembrolizumab monotherapy can provide durable clinical benefit with manageable toxicity in this hard-to-treat patient population.”
The exploratory analysis included 19 patients from the phase Ib KEYNOTE-028 trial that restricted participation to those with PD-L1-positive tumors and 64 patients from the phase II KEYNOTE-158 trial that did not have any restrictions based on PD-L1 levels.
Over a median follow-up of 7.7 months, 19.3% of participants achieved an overall response to pembrolizumab monotherapy, with two complete and 14 partial responses. An additional 15 participants had stable disease as their best response.
The median duration of response was not reached at the time of analysis, and the estimated proportion of patients with a response lasting for at least 18 months was 61%.
Progression-free survival was a median of 2.0 months and median overall survival was 7.7 months; the respective rates at the 12-month mark were 16.9% and 34.3%.
Seven percent of patients experienced treatment-related adverse events of grade 3, and although there were no grade 4 events, two deaths were attributed to treatment-related toxicity (one case each of pneumonia and intestinal ischemia).
“Our findings are particularly noteworthy given that data show that historically, patients with SCLC in the third-line treatment setting have limited survival benefit, with a median [duration of response] of less than two months and median survival of around two to three months,” said Chung in a press release.
And he concluded: “This pooled analysis supports the use of pembrolizumab monotherapy for patients with extensive-stage SCLC as third-line or later therapy.”
Noting that relapsed extensive-stage SCLC is “a disease setting where responses are rare, long-term survival is unheard of, and duration of responses can be measured almost in minutes as opposed to in months", commentator Louis Weiner (Georgetown Lombardi Comprehensive Cancer Center, Washington, DC, USA) described the analysis as “an important advance.”
“It builds upon a substantial body of work that has already been performed but knowing that this treatment can be effective – with a 20% response rate – in heavily pretreated patients with extensive-stage SCLC is a major observation and a great comfort to our patients and their treating physicians,” he remarked.
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