The programmed death 1 (PD-1) inhibitor pembrolizumab demonstrated a clinically significant 24.8% overall response rate in patients with recurrent or metastatic squamous cell carcinoma of the head and neck (SCCHN), according to the results of a late-breaking abstract (LBA6008) presented at the 2015 American Society of Clinical Oncology (ASCO) Annual Meeting held May 29 to June 2 in Chicago.
“If you put this into perspective for the treatment of head and neck cancer, our best approved targeted therapy is cetuximab, with a response rate of 10% to 13%,” said study author Tanguy Seiwert, MD, an assistant professor of medicine and associate HNC program leader at the University of Chicago. “This is twice as good as our best targeted therapy in this early preliminary report.”
The KEYNOTE-012 expansion cohort study included 132 patients with recurrent or metastatic SCCHN who were assigned to receive 200 mg of pembrolizumab every 3 weeks regardless of PD-ligand 1 (L1) expression or human papillomavirus (HPV) status. The primary endpoint of the study was overall response rate.
Evaluating 117 patients, the overall response rate was 24.8%, indicating that about one in four patients responded. The response rate was 20.6% in patients with HPV-positive disease and 27.2% in patients with HPV-negative disease, showing that the drug is active in both entities. In addition, 24.8% of patients in the trial had stable disease.
Combined, this translated into a disease control rate of about 50%, which Seiwert said was “remarkable in this disease, especially in a heavily pretreated population.”
Overall, 56% of patients had a decrease in the size of tumor lesions.
“When we looked at patients who did benefit, we saw that responses occurred as early as 8 weeks and 16 weeks, although there were a few outliers with late responses,” Seiwert said.
Those patients who did respond often had durable responses (86%), and many patients with stable disease continued on the study drug, with 40 patients still receiving therapy with pembrolizumab.
Seiwert said that the treatment was well tolerated. The most common adverse event was fatigue (15.2%). A few patients did experience more severe adverse events: Two patients had grade 3 pneumonitis and one patient had grade 3 colitis.
Evaluation of PD-L1 status for these patients is ongoing, Seiwert said.
In a statement released by ASCO, Gregory A. Masters, MD, FACP, FASCO, of Thomas Jefferson University Medical School, commented on these results: “This is yet another exciting example where PD-1 immunotherapy might work better and more reliably than existing drugs, and with fewer side effects. The diversity of patients who responded is greater than in any previous clinical trials. But, we still need larger studies and longer follow-up to assess the impact of this treatment on patient survival.”