Pembrolizumab for previously treated advanced anal squamous cell carcinoma: Pooled results from the KEYNOTE-028 and KEYNOTE-158 studies.
Aurélien Marabelle, Philippe A. Cassier, Marwan Fakih, Steven Kao, Dorte Nielsen, Antoîne Italiano, Tormod Kyrre Guren, Marloes van Dongen, Kristen Spencer, Giovanni M. Bariani, Paolo A. Ascierto, Armando Santoro, Sandrine Hiret, Patrick A. Ott, Sarina A. Piha‐Paul, Chih‐Chin Liu, Melanie A. Leiby, Kevin Norwood, Jean‐Pierre Delord
Abstract
4020 Background: Patients (pts) with anal squamous cell carcinoma (ASCC) have poor outcomes and few treatment options. We report a pooled analysis of pembrolizumab (pembro) antitumor activity and safety in the ASCC cohorts of the multicohort studies KEYNOTE-028 (NCT02054806; phase 1b) and KEYNOTE-158 (NCT02628067; phase 2), providing a robust sample size and longer follow-up. Methods: Eligible pts were aged ≥18 y with histologically/cytologically confirmed metastatic/unresectable ASCC, had prior failure of/intolerance to standard therapy or no standard therapy options, measurable disease (RECIST v1.1), ECOG PS 0/1, and a tissue sample evaluable for PD-L1/biomarkers (KEYNOTE-028 required PD-L1 positivity). Baseline PD-L1 expression was assessed using a prototype IHC assay (QualTek) in KEYNOTE-028 and the PD-L1 IHC 22C3 pharmDx assay (Agilent Technologies) in KEYNOTE-158. Pts received pembro 10 mg/kg Q2W (KEYNOTE-028) or 200 mg Q3W (KEYNOTE-158) for 2 y or until PD/unacceptable AEs. The primary endpoint in both studies was ORR (per RECIST v1.1). Secondary endpoints were duration of response (DOR), PFS, OS, and safety. Results: 137 pts with ASCC were treated in KEYNOTE-028 (n = 25) or KEYNOTE-158 (n = 112) and were included in this analysis (median age, 61 y; 83.2% women; 73.0% had PD-L1–positive tumors). Median follow-up was 11.7 mo; 124 pts (90.5%) had discontinued treatment. ORR (95% CI) was 10.9% (6.3%–17.4%). 8 pts had CR and 7 had PR. ORR (95% CI) by PD-L1 status was 14.0% (7.9%–22.4%) in the PD-L1 positive group and 3.3% (0.1%–17.2%) in the PD-L1 negative group. Among all treated pts, median DOR was not reached (range, 6.0+ to 57.5+ mo). By Kaplan-Meier estimation, 84.6% of responders had a DOR ≥24 mo. Median PFS was 2.1 mo (95% CI, 2.0–2.1) and median OS was 11.7 mo (95% CI, 8.8–14.5). The 12-mo PFS and OS rates were 14.5% and 47.4%. 85 pts (62.0%) had +1 treatment-related AE, 24 pts (17.5%) with grade 3–4 events (no grade 5 events). 32 pts (23.4%) had immune-mediated AEs; 2 pts (1.5%) had infusion related reactions. Conclusions: In pts with previously treated advanced ASCC, pembro showed durable antitumor activity, particularly in pts with PD-L1–positive tumors, and manageable toxicity. Clinical trial information: NCT02054806 (KEYNOTE-028), NCT02628067 (KEYNOTE-158) .