The following article features coverage from the 2017 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago, Illinois. Click here to read more of Cancer Therapy Advisor‘s conference coverage.

Maintenance pembrolizumab does not prolong progression-free survival (PFS), though it may improve overall survival (OS), among patients with extensive-stage small-cell lung cancer (ES-SCLC), according to data presented at the 2017 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago.1

Shirish M. Gadgeel MD, of the Karmanos Cancer Institute in Detroit, Michigan, reported this phase 2 study ( Identifier: NCT02359019).

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Median PFS and OS rates are about 2 and 7 months, respectively, after chemotherapy in this patient population. “Maintenance setting was considered ideal because patients have a better performance status [vs at diagnosis or relapse], tumor debulking may improve immune clearance, and shorter PFS after discontinuation of chemotherapy allows for rapid assessment of clinical endpoints,” Dr Gadgeel said.

Patients with ES-SCLC enrolled in the study were required to begin maintenance therapy within 8 weeks of completing chemotherapy.

Of 45 patients enrolled, 56% were male and 22% had brain metastases. Median time from end of chemotherapy to start of pembrolizumab was 5 weeks. Thirty-five patients had measurable disease at study entry.

Blood samples were collected prior to the first, second, and third cycles of pembrolizumab to determine circulating tumor cell (CTC) counts.

With a median PFS of 1.4 months, maintenance pembrolizumab did not achieve it primary endpoint. Immune-related PFS was 4.7 months.

Median OS was 9.4 months, with a 6-month OS of 72% and 12-month OS of 30%.

Median PFS for patients with positive PD-L1 staining at stromal interface was improved (5.5 vs 1.3 months for patients who were PD-L1-negative).

Disease control rate was 42% (1 complete response, 3 partial responses, and 15 patients with stable disease).

The authors noted that the “median CTC prior to [pembrolizumab] was 1 (0-256, n=37 [patients]). Each unit increase in baseline CTC correlated with worse PFS.”

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The most common any-grade adverse events were fatigue, pruritus, and nausea.

“Ongoing studies will define the role of pembrolizumab in this patient population,” Dr Gadgeel said.

Read more of Cancer Therapy Advisor‘s coverage of the 2017 American Society of Clinical Oncology (ASCO) Annual Meeting by visiting the conference page.


  1. Gadgeel SM, Ventimiglia J, Kalemkerian GP, et al. Phase II study of maintenance pembrolizumab (pembro) in extensive stage small cell lung cancer (ES-SCLC) patients (pts). J Clin Oncol. 2017;35(suppl; abstr 8504).