Pembrolizumab Did Not Improve PFS or OS Compared With Paclitaxel in Relapsed Gastric or Gastroesophageal Junction Cancer

Pembrolizumab did not improve progression-free survival (PFS) or overall survival (OS) compared with paclitaxel in patients with previously treated gastric or gastroesophageal junction (GEJ) cancer, according to data from the KEYNOTE-061 trial (ClinicalTrials.gov Identifier: NCT02370498) presented at the ESMO World Congress on Gastrointestinal Cancer 2018.¹

Results from the KEYNOTE-012 and -059 trials (ClinicalTrials.gov Identifers: NCT01848834 and NCT02335411, respectively) suggested that pembrolizumab had antitumor activity against relapsed/refractory gastric or GEJ cancer. The purpose of this trial was to evaluate the efficacy and safety of pembrolizumab in this population in a phase 3 trial.

The international, open-label, phase 3 KEYNOTE-061 trial randomly assigned 395 patients with advanced gastric or GEJ adenocarcinoma to receive pembrolizumab or paclitaxel. All patients had previously progressed after first-line treatment with platinum and fluoropyrimidine chemotherapy. The co-primary endpoints were OS and PFS in patients with a PD-L1 combined positive score (CPS) greater than or equal to 1.

The objective response rate was 15.8% with pembrolizumab and 13.6% with paclitaxel. Median PFS was also similar between groups at 1.5 and 4.1 months with pembrolizumab or paclitaxel, respectively (HR, 1.27; 95% CI, 1.03-1.57).

There was no significant difference in overall survival, with a median of 9.1 months (95% CI, 6.2-10.7 months) with pembrolizumab compared with 8.3 months (95% CI, 7.6-9.0 months) with paclitaxel (hazard ratio [HR], 0.82; 95% CI, 0.66-1.03) after a median of 8 months of follow-up. The 12- and 18-month OS rates were higher with pembrolizumab at 39.8% and 25.7%, respectively, compared with 27.1% and 14.8%, respectively, with paclitaxel. A post hoc analysis indicated that patients with a CPS greater than or equal to 10 demonstrated a prolonged median OS of 10.4 months with pembrolizumab compared with 8.0 months with paclitaxel (HR < 0.64; 95% CI, 0.41-1.02) and in tumors that had high microsatellite instability, regardless of CPS with a median OS not reached with pembrolizumab compared with 8.1 months with paclitaxel (HR, 0.42; 95% CI, 0.13-1.31).

The duration of response was longer with pembrolizumab at 18.0 months compared with 5.2 months with paclitaxel.

Grade 3 to 5 drug-related adverse events occurred in 34.8% of patients who received paclitaxel compared with 14.3% of patients who receive pembrolizumab. Discontinuation rates due to adverse events were 5.4% and 3.1% with paclitaxel and pembrolizumab, respectively.

The authors noted that “pembrolizumab had a better safety profile than paclitaxel,” and though this study did not show an improved OS with pembrolizumab, other trials of pembrolizumab monotherapy in gastric and GEJ cancers are ongoing.

Read more of Cancer Therapy Advisor‘s coverage of the ESMO World Congress on Gastrointestinal Cancer 2018 meeting by visiting the conference page.

Reference

1. Shitara K, Özgüroğlu M, Bang YJ, et al. KEYNOTE-061: Phase 3 study of pembrolizumab vs paclitaxel for previously treated advanced gastric or gastroesophageal junction (G/GEJ) cancer. Ann Oncol. 2018;29 (suppl 5;abstr LBA-005):v123. doi: 10.1093/annonc/mdy208.004