ASCO 2015 Report: Pembrolizumab shows “remarkable” efficacy in head and neck cancer

by Bruce Sylvester: Pembrolizumab (Keytruda®), an anti-PD-1 antibody immunotherapy has shown efficacy in one fourth of patients with recurrent or metastatic head and neck cancer, researchers reported on May 29 at the 2015 meeting of the American Society for Clinical Oncology (ASCO).

Pembrolizumab decreased tumors by 30 percent or more in 24.8 percent of 132 clinical trial patients. “The efficacy was remarkable,” said investigator Tanguy Seiwert, MD, assistant professor of medicine and associate program leader for head and neck cancer at the University of Chicago, “roughly twice as good as any drug combination in our arsenal.”

“Overall, 56 percent of patients experienced a measurable decrease in the size of their tumors,” Seiwert added.

Unlike epidermal growth factor receptor inhibitors, which appear to be less effective in HPV-positive tumors, pembrolizumab showed similar levels of activity in both HPV-associated and HPV-negative tumors.

The investigators enrolled 132 patients with recurrent or metastatic squamous cell carcinoma of the head and neck. They were treated every 3 weeks with a 200-mg infusion of pembrolizumab. Patients were not selected for this study based on PD-L1 status, a candidate biomarker that predicts response to PD-1/PD-L1 immunotherapy, such as pembrolizumab).

The objective response rate was 24.8 percent, with 26.3 percent response in HPV-negative subjects and 20.6 percent response in HPV-positive subjects.

Fifty-six percent of all subjects achieved target lesion shrinkage.

Less than 10 percent of subjects reported serious side effects. The most common were fatigue, rash, and pruritus. Three subjects reported more serious immune-related side effects, grade 3 pneumonitis and colitis.

“Our 25 percent response rate may underestimate the benefit in patients,” Seiwert added. “We know from other disease entities such as lung cancer–where the experience with immunotherapy is broader–that patients who have disease stabilization or even pseudo-progression may benefit in ways that translate into longer survival.”

ASCO expert commentator, Gregory A. Masters, MD, attending physician at the Helen F. Graham Cancer Center and Associate Professor at the Thomas Jefferson University Medical School in Philadelphia, said, “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.”

Pembrolizumab (Keytruda®), is FDA-approved for the treatment of advanced melanoma that has spread to other parts of the body or cannot be surgically removed.

Merck Sharp & Dohme Corp. funded the study.