Merkel Cell Carcinoma Treatment

Merkel cell carcinoma is an uncommon form of skin cancer that develops in specialized neuroendocrine cells found in the top layer of the skin (Merkel cells), which are involved in the sense of touch. Merkel cell carcinoma often first appears as a painless, firm, red or violet nodule on an area of skin frequently exposed to the sun, such as the face, neck, arms or legs.

Often fast-growing and aggressive, Merkel cell carcinoma is primarily caused by a combination of ultraviolet (UV) radiation exposure and infection with the Merkel cell polyomavirus. In many cases, the virus integrates into the DNA of skin cells and promotes uncontrolled cell growth. Individuals with a weakened immune system, including organ transplant recipients and those with certain blood cancers or human immunodeficiency virus (HIV), are at increased risk. Advanced age and fair skin also heighten susceptibility.

Though rare overall, Merkel cell carcinoma is becoming more common in the United States, where an estimated 3,000 to 3,500 new cases are diagnosed each year. Although the condition can affect anyone, it occurs most frequently in adults older than 65. Because the cancer tends to progress quickly and can spread to nearby lymph nodes and distant organs, an early diagnosis and prompt treatment are essential to achieve the best possible outcome and quality of life.

Treatment for Merkel cell carcinoma can vary depending on the size, location, stage and extent of the tumor and the patient’s overall health. In many cases, a multispecialty team will develop a tailored combination of therapies.

Surgery for Merkel cell carcinoma

Surgery is usually the first-line treatment for localized Merkel cell carcinoma, especially if the cancer is confined to the skin or nearby lymph nodes and can be removed completely. Surgical treatment may involve:

• Wide local excision to remove the tumor along with a margin of healthy tissue
• Sentinel lymph node biopsy to determine whether cancer has spread to nearby lymph nodes
• Lymph node dissection to remove affected lymph nodes

The goal of surgical treatment is to achieve clear margins, which means no cancer cells are seen at the edges of the removed tissue when viewed under a microscope. In many cases, surgery is followed by radiation therapy to target any remaining microscopic cancer cells and help reduce the risk of recurrence.

The risks and side effects of surgery for Merkel cell carcinoma may include pain, bleeding, infection, scarring and limited movement if lymph nodes are removed. Additionally, swelling due to lymph fluid buildup (lymphedema) can occur after lymph node dissection.

Merkel cell is another aggressive form of skin cancer, similar in many ways to melanoma, but with fewer early warning signs.

Vernon Sondak, MD

Chair, Cutaneous Oncology Program

Radiation therapy for Merkel cell carcinoma

Radiation therapy is a standard treatment for many patients with Merkel cell carcinoma. This localized therapy, which uses high-energy beams to destroy cancer cells, is often administered after surgery to reduce the risk of recurrence. It may also be used as a primary treatment if surgery is not feasible or to relieve symptoms associated with advanced or metastatic cancer.

Radiation delivery techniques that may be used for treating Merkel cell carcinoma include:

• External beam radiation therapy (EBRT)
• Image-guided radiation therapy (IGRT)
• Intensity-modulated radiation therapy (IMRT)

The side effects of radiation therapy can vary based on the dose and treatment site. Some patients may experience skin irritation, redness, fatigue or temporary hair loss in the area of the body treated. Most side effects are temporary and improve shortly after treatment ends.

Immunotherapy for Merkel cell carcinoma

Immunotherapy is frequently used to address recurrent or inoperable cancer, and it has become a cornerstone of treatment for advanced Merkel cell carcinoma. The goal is to stimulate the body’s immune system to better recognize and attack cancer cells.

Immunotherapy drugs currently approved for treating Merkel cell carcinoma include:

• Avelumab
• Nivolumab
• Pembrolizumab

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Known as immune checkpoint inhibitors, these medications target specific proteins found on the surface of cancer cells, such as PD-1 and PD-L1. This can help the immune system mount a stronger response against the tumor.

Immunotherapy is often recommended for patients whose cancer has spread or returned after initial treatment. In some cases, it may be considered as a first-line treatment for advanced or metastatic disease.

During immunotherapy, side effects may occur due to increased immune system activity. Common experiences include fatigue, rash, diarrhea and inflammation of organs, such as the thyroid, lungs or liver. Although many side effects are manageable, close monitoring is essential throughout treatment to prevent complications and maintain quality of life.

Chemotherapy for Merkel cell carcinoma

Chemotherapy is a systemic treatment that uses powerful drugs to target and destroy rapidly dividing cells throughout the body. Though once considered the primary treatment for advanced Merkel cell carcinoma, it is now used less frequently due to the effectiveness and durability of immunotherapy. That said, chemotherapy may still be considered if immunotherapy is inappropriate or ineffective. It may also be an option for rapidly progressing metastatic cancer or used to help relieve symptoms.

Chemotherapy drugs that may be used to treat Merkel cell carcinoma include:

• Carboplatin
• Cisplatin
• Etoposide
• Topotecan

While chemotherapy for Merkel cell carcinoma may produce an initial response, it is often temporary. Side effects can include nausea, vomiting, hair loss, fatigue, increased risk of infection and nerve damage. Because chemotherapy can affect healthy cells that naturally divide rapidly, careful monitoring is required during treatment.

Targeted therapy and other treatment options for Merkel cell carcinoma

Targeted therapy uses medications designed to interfere with specific molecular changes that help cancer cells grow and survive. At this time, there are no widely established targeted therapies approved specifically for Merkel cell carcinoma, but researchers continue to evaluate potential options in ongoing studies and clinical trials. Because Merkel cell carcinoma is not driven by hormones, endocrine therapy is not an effective treatment approach.

Clinical trials for Merkel cell carcinoma

Clinical trials are carefully designed research studies that evaluate the effectiveness of emerging treatments and novel combinations of existing therapies compared to the current standard of care. Participation in a clinical trial may provide the patient with access to promising new therapies before those options are made widely available in other settings. Clinical trials also help scientists improve treatment strategies and advance the understanding of Merkel cell carcinoma.

Benefit from world-class care at Moffitt Cancer Center

At Moffitt, patients with Merkel cell carcinoma can receive individualized care from a multispecialty team of experts in surgical oncology, radiation oncology, medical oncology and supportive services. Treatment plans are tailored to each patient’s diagnosis and personal needs, incorporating the latest research and evidence-based approaches.

If you would like to learn more about Merkel cell carcinoma treatment, you can request an appointment with a specialist in the Cutaneous Oncology Program at Moffitt by calling 1-888-663-3488 or submitting a new patient registration form online. We do not require referrals.