There are multiple treatment options for Merkel cell carcinoma. Treatment is usually based on stage of the disease. An important aspect of proper care for Merkel cell carcinoma is often a sentinel lymph node biopsy prior to wide surgical excision to test if the cancer has spread to the local lymph nodes.
Treatment for early stage Merkel cell carcinoma
If you have early stage Merkel cell carcinoma (stage I and II when the primary tumor has not spread to lymph nodes or other parts of the body) then your treatment will likely involve surgery to remove the tumor, often followed by radiation to the tumor site and possibly the regional lymph nodes. Wide surgical excisions are used to take out the cancer and some of the skin around the tumor.
“Merkel cell carcinoma stands out from other skin cancers in several ways that have important implications for treatment,” says Merkel cell carcinoma expert Paul Nghiem, MD, PhD, at Seattle Cancer Care Alliance. “Surgery can be effective for Merkel cell carcinoma but unlike in melanoma, surgery alone has very high local recurrence rates for this disease.
“Merkel cell carcinoma is a cancer that spreads discontinuously,” Nghiem explains. “So when doctors remove a cancerous area, it may appear they got it all. For instance, the margins around the excised tissue may be free of cancer cells when examined under the microscope. But there are often cancer cells left in the adjacent tissue that will grow and make their presence known over time.
“The other important thing about this cancer is that it’s very sensitive to radiation,” says Nghiem. Radiation therapy uses high-energy X-rays to kill cancer cells and shrink tumors. External radiation therapy is therefore often used to treat Merkel cell carcinoma.
“There is some evidence that in some people radiation alone may be a viable treatment option. Treating Merkel cell carcinoma with radiation alone mostly makes sense when surgery would need to be very extensive or if surgical options are not available due to the patient’s medical condition,” he adds. “But in any case, radiation plays a uniquely important role in this skin cancer.”
Treatment for advanced Merkel cell carcinoma
People with more advanced Merkel cell carcinoma that has spread to nearby lymph nodes but not to other parts of the body (i.e. stage III) are likely to receive surgery followed by radiation to the primary site as well as the regional lymph nodes.
If Merkel cell carcinoma has spread distantly (i.e. stage IV), patients generally need systemic therapy instead of local therapy. Until recently, the standard systemic option used to be chemotherapy, which would shrink many tumors but only provide about three months of cancer control. However, many recent trials have resulted in a major shift toward using treatments designed to stimulate the immune system in Merkel cell carcinoma. The most promising emerging option to treat Merkel cell carcinoma is a class of drugs called immune checkpoint inhibitors.
In March 2017, immune checkpoint inhibitor avelumab (Bavencio) became the first FDA-approved treatment for metastatic Merkel cell carcinoma after being studied in a clinical trial, for which SCCA was one of the leading sites. In the study, avelumab was used to treat 88 patients who had metastatic Merkel cell carcinoma that had come back despite at least one round of chemotherapy. Twenty-eight of those patients’ tumors shrank or disappeared in response to avelumab, and 23 of those 28 have not seen their cancers grow again in the average of 10 months since they started treatment, according to study data published in September 2016.
SCCA’s principal investigator on the trial, Shailender Bhatia, MD, comments, “Several patients received avelumab at SCCA through this clinical trial that started in 2015. These patients were desperately seeking an effective option at that time. Happily, many of these patients are doing well without evidence of active cancer. What has been most remarkable is that patients have had very good quality-of-life while receiving this therapy.”
Minimizing immunosuppression is very important in this disease, too—“unusually important compared to other skin cancers,” says Nghiem. People whose immune system isn’t functioning at a normal level are at increased risk for Merkel cell carcinoma. For instance, people whose immune systems are suppressed because of human immunodeficiency virus (HIV), a solid organ transplant, or chronic lymphocytic leukemia or another cancer are 10 to 20 times more likely to get Merkel cell carcinoma and much more likely to die of it once they’ve got it.
Minimizing patients’ immunosuppression can become part of the therapy for Merkel cell carcinoma. If there’s any way to decrease the immunosuppression, this may help the body control the cancer.