Phase II Study of Maintenance Pembrolizumab in Patients with Extensive-Stage Small Cell Lung Cancer (SCLC)

doi:10.1016/j.jtho.2018.05.002

Journal of Thoracic Oncology

Volume 13, Issue 9, September 2018, Pages 1393-1399

Presented in part at the 2017 Annual Meeting of the American Society of Clinical Oncology. June 2–6, 2017; Chicago, IL.

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Abstract

Objective

The aim of this study was to assess the efficacy of maintenance pembrolizumab in patients with extensive-stage SCLC after treatment with platinum and etoposide.

Methods

Patients with extensive-stage SCLC with a response or stable disease after induction chemotherapy were eligible. Pembrolizumab at a dose of 200 mg administered intravenously every 3 weeks was initiated within 8 weeks of the last cycle of chemotherapy. The primary end point of the study was progression-free survival (PFS) from study registration, with overall survival (OS) as a key secondary end point. Available tumor tissue was assessed for expression of programmed death ligand 1 (PD-L1) both in the tumor cells and in the surrounding stroma. Blood for circulating tumor cells was collected before the first, second, and third cycles of pembrolizumab.

Results

Of the 45 patients enrolled, 56% were male and 22% had treated brain metastases. The median PFS was 1.4 months (95% confidence interval [CI]: 1.3–2.8), with a 1-year PFS of 13%. The median OS was 9.6 months (95% CI: 7.0–12), with a 1-year OS of 37%. Of the 30 tumors that could be assessed, three had PD-L1 expression (≥1%) in the tumor cells. A total of 20 tumors could be assessed for PD-L1 expression in the stroma. The median PFS in the eight patients with tumors positive for expression of PD-L1 at the stromal interface was 6.5 months (95% CI: 1.1–12.8) compared with 1.3 months (95% CI: 0.6–2.5) in 12 patients with tumors negative for this marker. No unexpected toxicities were observed.

Conclusion

Maintenance pembrolizumab did not appear to improve median PFS compared with the historical data. However, the 1-year PFS rate of 13% and OS rate of 37% suggest that a subset of patients did benefit from pembrolizumab.

Keywords

SCLC

Maintenance

Pembrolizumab

Metastatic

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: Disclosure: Dr. Gadgeel reports grants from Merck during the conduct of the study and personal fees from Genentech/Roche, Astra-Zeneca, Ariad/Takeda, and Abbvie outside the submitted work. Dr. Pennell reports personal fees from Eli Lilly, AstraZeneca, and Regeneron outside the submitted work. Dr. Fidler reports personal fees from Genentech/Roche, Abbvie, Boehringer Ingelheim, Takeda, AstraZeneca, Celegene, and Merck outside the submitted work. Dr. Halmos reports grants from Merck, AstraZeneca, and Mirati; personal fees from Genentech, Foundation Medicine, Guardant Health 360, and Ignyta; and grants and personal fees from Novartis, Boehringer Ingelheim, Pfizer, and Takeda outside the submitted work. Dr. Bonomi reports personal fees from Astra Zeneca, Biodesix, Genentech, Imedex, Merck, Pfized, Spectrum, and Trovagene outside the submitted work. Dr. Stevenson reports grants from Merck during the conduct of the study, as well as grants from Merck, Bristol-Myers Squibb, Bayer, and Aduro Biotech outside the submitted work. Dr. Sukari reports grants from Eisai and personal fees from Merck outside the submitted work. Dr. Wozniak reports personal fees from Boehringer Ingelheim, AstraZeneca, and Takeda, as well as grants from Boehringer Ingelheim outside the submitted work. Dr. Kalemkerian reports grants from Merck outside the submitted work. The remaining authors declare no conflict of interest.