Pembrolizumab in Advanced PD-L1–Positive Endometrial Cancer


Key Points

  • Three previously treated patients (13%) with advanced PD-L1–positive endometrial cancer responded to pembrolizumab.
  • The durations of response were 64.3, 63.7+, and 64.7+ weeks.

Pembrolizumab (Keytruda) showed activity in previously treated patients with advanced programmed cell death ligand 1 (PD-L1)–positive endometrial cancer in a cohort of the phase Ib KEYNOTE-028 study. These findings were reported in the Journal of Clinical Oncology by Ott et al.

Study Details

A total of 24 patients with PD-L1–positive disease (defined as membranous staining in ≥ 1% of tumor and associated inflammatory cells or positive staining in stroma on immunohistochemistry) whose disease had progressed after standard therapy received pembrolizumab at 10 mg/kg every 2 weeks for up to 24 months, disease progression, or unacceptable toxicity. Fifteen patients had received at least two previous lines of therapy for advanced disease. Data cutoff was in February 2016.


A confirmed partial response was observed in three patients (13.0%, 95% confidence interval = 2.8%–33.6%). All 3 responses were among 17 patients with endometrioid adenocarcinoma. Of 19 patients evaluable for microsatellite instability (MSI) status, only 1 had MSI-high status; this patient had progressive disease as best response. One responder had non–MSI-high status but exhibited a polymerase E mutation. The median duration of response was not reached; in two patients, response was ongoing at 63.7+ and 64.7+ weeks at data cutoff, with the duration of response in the remaining patient being 64.3 weeks. Stable disease was observed in three additional patients (13.0%), with a median duration of 24.6 weeks.

Adverse Events

Treatment-related adverse events occurred in 13 patients (54.2%), with the most common being fatigue (20.8%), pruritus (16.7%), pyrexia (12.5%), and decreased appetite (12.5%). Grade 3 treatment-related adverse events occurred in four patients (16.7%), with adverse events consisting of asthenia and back pain in one; anemia, hyperglycemia, and hyponatremia in one; chills and pyrexia in one; and diarrhea in one. No patients experienced a grade 4 adverse event or an immune-mediated adverse event of any grade, and no patients discontinued treatment due to adverse events.

The investigators concluded: “Pembrolizumab demonstrated a favorable safety profile and durable antitumor activity in a subgroup of patients with heavily pretreated advanced PD-L1–positive endometrial cancer.”

The study was supported by Merck.

Patrick A. Ott, MD, PhD, of Dana-Farber Cancer Institute, is the corresponding author of the Journal of Clinical Oncology article.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.