Merkel Cell Carcinoma

Merkel cell carcinoma is a rare and aggressive form of skin cancer. It’s most often caused by the Merkel cell polyomavirus. However, it can also occur as a result of exposure to ultraviolet light and for some patients, the cause is unknown. Most people diagnosed with this disease are older and already have a suppressed immune system.

Typical treatment for Merkel cell carcinoma includes chemotherapy. However, according to a recent study conducted by the Johns Hopkins Kimmel Cancer Center, immunotherapy may actually be more effective and provide better outcomes for patients.

Immunotherapy vs. Cancer

Immunotherapy helps the body fight the cancerous cells itself by removing constraints that are stopping the body’s immune system from fighting back.

This study was the earliest and longest trial of any immunotherapy as the primary treatment for this disease. It investigated pembrolizumab for merkel cell carcinoma. Pembrolizumab was recently granted FDA accelerated approval. It is the first-line immunotherapy treatment to receive approval for this condition.

How does it work?

PD-1 is a molecule that regulates immune responses in the body. Pembrolizumab works to block this molecule. This means the cancer cells can’t manipulate it to stop the immune system. This manipulation is what normally allows cancerous cells to take over in the body. Instead, by blocking PD-1, immune cells react by attacking cancer cells.

The Study

This study, like many, was made possible because of collaboration between numerous medical centers. Eleven centers in total were involved across the United States including the Fred Hutchinson Cancer Research Center. However the Kimmel Cancer Center at Johns Hopkins was the lead institution.

It included 50 patients total. They all had recurrent, metastatic, or locally advanced Merkel cell carcinoma. Some patients had virus-positive carcinomas and some had virus-negative. For both types, response to treatment was positive overall.

All participants received pembrolizumab every three weeks, some for as long as two years. They were periodically monitored using imaging scans. 56% of the participants (28 patients) had a long-lasting response to treatment with immunotherapy. 24% (12 patients) had their tumors completely disappear. 70% of participants were still alive two years after treatment with immunotherapy had begun. Unfortunately, serious side effects were documented in 28% of patients with one treatment-associated death.

These results overall show that immunotherapy is a more effective treatment option than chemotherapy for patients with Merkel cell carcinoma. Patients in the trial had a better overall response to treatment and longer survival when treated with pembrolizumab than what would have been expected had they been treated with chemotherapy.

Looking Forward

Researchers hope that the findings from this study will help lead the way for development of similar treatments for other cancers which are associated with viruses. Virus-related cancers account for approximately 20% of all cancers and this study has indicated that immunotherapy could be a new pathway to investigate for many of these conditions.