In a new study led by scientists at the Fred Hutchinson Cancer Research Center and the Johns Hopkins Kimmel Cancer Center, where they did a clinical trial of the immunotherapy drug pembrolizumab using a sample of 26 patients with a rare type of virus-linked skin cancer called Merkel cell carcinoma (MCC), it was found that in half of them, and due to the drug, the tumor shrunk substantially. The effects were lasting nearly three times as long, on average, than with conventional chemotherapy. Several patients had no remaining evidence of disease. This drug can, then, boost the immune system’s ability to kill tumor cells.

The 26 patients were not diagnosed with metastatic MCC. The process consisted in treating them with 2 mg/kg of intravenous pembrolizumab every 3 weeks for up to 2 years. Twenty-five of the 26 patients had at least 1 radiologic assessment. Tumors were evaluated every 9 or 12 weeks. The primary endpoint was measured objectively with the Response Evaluation Criteria In Solid Tumors (RECIST) criteria, evaluating the improvement of the tumor. Median follow-up was 7.6 months.

The FDA recently approved three new immunotherapy drugs called PD-1 inhibitors. Credit: Popular Science

The improvement rate was 56 percent, meaning that in 14 people the tumor shrunk. Among responders, 16 percent, or 4 people, had a complete response and 40 percent, or 10 people, had a partial response. One patient had an unconfirmed partial response, one had stable disease, and 36 percent (9 people) had progressive disease.

The scientists say the results could be a new way to treat patients with other virus-associated cancers, in the future. This study helps to see how the patients may react to the drugs.

Merkel cell carcinoma is diagnosed in about 1,500 annually in the United States. It is also classified as an “orphan disease.” It tends to occur in older people and those who have suppressed immune systems, says William Sharfman, M.D., an associate professor of oncology and dermatology and director of cutaneous oncology at the Johns Hopkins Kimmel Cancer Center. He adds that around 80 percent of Merkel cell carcinomas are caused by a virus called Merkel cell polyomavirus, and the rest are caused by exposure to ultraviolet light and other unknown factors, and as far as right now, there is no approved therapy.

More than 40 percent of patients who develop MCC on their skin develop advanced disease, with a poor long-term survival of approximately 10 percent and median survival of about 1 year.

The results of the study are expected to be presented at the American Association for Cancer Research (AACR) Annual Meeting 2016 in New Orleans.

“What we found in this preliminary study of patients with Merkel cell cancer may not be true for every virus-induced cancer,” says Suzanne Topalian, M.D., professor of surgery and oncology and associate director of the Bloomberg Kimmel Institute for Cancer Immunotherapy. “But if additional studies with more patients confirm our findings, we will have strong reason to believe that many cancers with virus-linked proteins could be valid targets for immune checkpoint blockade.”

Source: The American Cancer Society