Treatment
Surgery followed by radiation therapy is the primary treatment for Merkel cell carcinoma. Chemotherapy may be used in more advanced cases in which the cancer has spread. Here are some of the procedures the doctor may recommend:
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Wide Local Excision
In this surgical procedure, the tumor is removed along with a margin of healthy tissue. The doctor will also perform a sentinel lymph node biopsy at the same time as this procedure. If cancer is found in the sentinel node, the doctor will perform a lymph node dissection as well, usually at a later date, since the cancer in the lymph nodes is not easy to identify while in the first operation. It is important for almost everyone with Merkel cell carcinoma to have a sentinel lymph node biopsy, due to the highly aggressive nature of the disease.
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Mohs Surgery
The doctor will remove the tumor by removing very thin layers of skin and examining them under a microscope for cancer cells. The doctor will keep removing thin layers until no more cancer cells are present. This procedure allows the doctor to remove as little healthy skin as possible to minimize discomfort and scarring. This procedure is often used to remove Merkel cell carcinomas on the face, if it is not possible to perform a wide excision with adequate margin.
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Lymph node dissection
Lymph nodes in your body are arranged in groups, called basins. The lymph node basins that receive direct lymphatic drainage from the primary tumor are called regional lymph nodes. With Merkel cell carcinoma, spread to the regional lymph nodes is very common. If the sentinel lymph node biopsy (SLNB) detects cancer cells on pathological examination under a microscope, the doctor may recommend a subsequent lymph node dissection to remove the lymph nodes in the basin.
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Radiation Therapy
External beam radiation therapy uses waves of high energy rays to target and kill cancer cells. In external beam radiation, a large machine delivers radiation to your tumor from outside the body. Radiation therapy is often used after surgery, to kill any remaining cancer cells in the area of the primary tumor on the skin. If lymph nodes are removed, you may also receive adjuvant radiation to the nodal basin to reduce the risk of a regional recurrence.
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Immunotherapy
In 2017, the treatment options for Merkel cell carcinoma improved considerably when the US Food and Drug Administration approved avelumab, the first drug cleared for treating Merkel cell carcinoma. In the class of immunotherapies known as the "checkpoint inhibitors" avelumab disables the PD-L1 (programmed cell death 1 ligand) protein on cancer cells, activating and allowing the patient's own immune system to attack the cancer cells.
The approval of this therapy was based on the findings from part A of the JAVELIN Merkel 200, an international clinical trial that involved 88 patients with advancer (stage IV, metastatic) Merkel cell carcinoma. All of these patients had received previous treatment, and all were subsequently treated with avelumab in the trial. After 10 months, 32% of the patients responded to the treatment, and among these patients, 92% responded for at least 6 months.
In part B of JAVELIN Merkel 200, investigators evaluated avelumab as the first choice of treatment for patients with stage IV, metastatic Merkel cell cancer. Among the 29 patients who were followed up for at least 3 months, 62% responded to the treatment. Among 14 patients who were followed for at least 6 months, 71% responded. Other checkpoint inhibitor drugs may also be used in metastatic disease. These include nivolumab or pembrolizumab. Novel clinical trials are evaluating these drugs in earlier stage Merkel cell disease. It is important to ask your physician if you are eligible to participate in such trial. This information on these new drugs has now changes the outlook for patients with advanced Merkel cell carcinoma. Earlier stage disease is still treated with surgery and radiation.
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Chemotherapy
Chemotherapy is the use of drugs to target rapidly growing cells in an effort to destroy cancer cells. For patients with Stage III or IV Merkel cell carcinoma, the medical oncologist might also recommend enrolling in a clinical trial of chemotherapy. Doctors may also use chemotherapy as a palliative treatment for stage IV Merkel cell carcinoma that has spread to other parts of the body. however, based on information regarding immunotherapy, the checkpoint inhibitors are now considered the new standard treatment for patients with metastatic disease.
Clinical Trial Information
Clinical trials allow patients to try a new treatment before it is available to the general public. In some cases, this may be a new drug that has not been used in humans before, or it may be a drug or drug combination that is not currently used for that specific type of cancer. Early phase clinical trials are often used to test side effects of a drug or drug combination, while later phase clinical trials are used to see how effective a new treatment might be for a certain type of cancer. Clinical trials allow doctors and researchers to improve the treatment of cancers with possibly more effective therapies. A clinical trial may be a new, groundbreaking drug or it may have no effect. It is important to talk with your doctor about the pros and cons of clinical trials for your particular situation.
