Immunotherapy Advances Treatment for MCC

Last updated: March 2020

Merkel Cell Carcinoma (MCC) is a rare and aggressive neuroendocrine skin cancer. MCC can develop from the uncontrolled growth of certain skin cells that share some characteristics with normal Merkel cells.3 It most commonly appears in people over age 60 in areas of the body that are exposed to the sun, including the head, neck, and arms. It is often fatal.2

The impact of MCC in numbers

There are approximately 1,600 new MCC cases each year in the US. The diagnosis rate rose by 95% between 2000 and 2013.2 Findings reported in the Journal of Clinical Oncology suggest the professional consensus, noted in the National Comprehensive Cancer Network guidelines, is that immunotherapy should be the first line of treatment for advanced MCC unless there are contraindications to PD-1 pathway blockade therapy. The results were reported by Dr. Paul Nghiem, lead author and professor of dermatology at the University of Washington.

Immunogenic cancer

MCC is considered an immunogenic cancer. This means it develops 10 times more often in people who are chronically immunosuppressed. Cytotoxic chemotherapy, a systemic treatment, was previously the only option available treating MCC. Improvement was limited with a median progression-free survival of approximately 90 days.2 However, benefits of alternative immunotherapy are nearly twice as effective in cases where people have not been previously treated with chemotherapy.2

Immunotherapy treatment approved

New studies show that treatment with pembrolizumab, produced by Merck and branded as Keytruda, can prolong survival when used as a first-line treatment for advanced Merkel Cell Carcinoma. Approved by the FDA in December 2018, pembrolizumab is indicated for the treatment of adult and pediatric patients with recurrent locally advanced or metastatic MCC.

Immunotherapy works with the body’s immune system to fight some kinds of cancer by sending T cells to detect and fight the presence of infections and diseases. Cancer cells can use the PD-1 (programmed cell death) pathway to hide from T cells. This prevents T cells from attacking cancer cells, allowing them to spread.

Proteins in your body

PD-1 and PD-L1 are proteins found on cells in your body. When bound together, they can prevent T cells from killing cancer cells. Pembrolizumab is an anti-PD1 therapy. Part of the research looked at the distance between PD-1–positive (receptor) and PD-L1 positive (ligand) cells within the tumor. They found that when the cells were closer it was predictive of a positive response to pembrolizumab.2

Immunotherapy improves MCC treatment outcomes

Immunotherapy helped patients achieve better tumor control, manageable levels of toxicity and longer survival when compared with prior data collected from patients who were treated with systemic chemotherapy. Pembrolizumab has been shown to have a tolerable safety profile.2

Results show immunotherapeutic treatments are improving overall quality of life and survival for people with MCC. Research reflects improvement in targeted treatments, but what we know now does not yet identify predictably reliable biomarkers which can answer whether an immune checkpoint inhibitor, like pembrolizumab, is the most appropriate course of treatment. As the incidence of MCC continues to rise as people age and many become immunocompromised, future research is still needed to identify improved treatments for people with MCC.

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