Pembrolizumab has durable effect in previously treated MSI-H/dMMR advanced endometrial cancer

Longer follow-up from the phase 2 KEYNOTE-158 trial showed pembrolizumab to have promising and long-standing efficacy in patients with previously treated MSI-H/dMMR advanced endometrial cancer.

Treatment options for previously treated, advanced, microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR) tumours are limited. Pembrolizumab showed a durable and clinically meaningful benefit in previously treated, advanced MSI-H/dMMR tumours – including endometrial cancer – in the non-randomised, open-label, phase 2 KEYNOTE-158 study (NCT02628067) [1]. Prof. David O’Malley (Ohio State University, USA) presented longer follow-up data in 90 patients with previously treated, advanced, MSI-H/dMMR endometrial cancer [2].

Patients received pembrolizumab (200 mg every 3 weeks) for up to 35 cycles. Primary endpoint was overall response rate (ORR); secondary endpoints included duration of response (DOR), progression-free survival (PFS), overall survival (OS), and safety.

At data cut-off, 18/90 patients (20%) had completed 35 cycles of pembrolizumab and 52 patients (58%) had discontinued treatment. In the efficacy population (n=79), median time from first dose to data cut-off was 42.6 month. ORR was 48%, with DOR ≥3 years in 68 patients. Median PFS was 13.1 months, PFS rates at 24, 36, and 48 months were 41%, 37%, and 37%. Median OS was not reached, OS rates at 24, 36, and 48 months were 64%, 60%, and 60% (see Figure).

Figure: PFS and OS results from KEYNOTE-158 [2]



Treatment-related adverse events were observed in 68/90 patients (76%). Immune-mediated adverse events and infusion reactions were observed in 25 patients (28%).

Based on these results, Prof. O’Malley concluded that “pembrolizumab monotherapy represents a promising treatment option for patients with previously treated, MSI-H/dMMR, advanced endometrial cancer.”

1. Marabelle A, et al. J Clin Oncol. 2020;38:1-10.
2. O'Malley DM. Et al. Pembrolizumab (pembro) in patients (pts) with microsatellite instability-high (MSI-H) advanced endometrial cancer (EC): Updated results from KEYNOTE-158. Abstract 795MO, ESMO Congress 2021, 16–21 September.

 

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Posted on 19 November, 202115 February, 2024