Treatments for Merkel cell carcinoma

Merkel cell carcinoma is a rare type of non-melanoma skin cancer. It starts in the Merkel cells, which are found in the deepest part of the top or outer layer of skin (epidermis). Merkel cells are close to nerves and help give the sense of touch.

Merkel cell carcinoma is also called neuroendocrine cancer of the skin or trabecular carcinoma.

Merkel cell carcinoma usually develops in people over 50 years old who have had significant UV light exposure. They may also have a weakened immune system from conditions such as chronic lymphocytic leukemia (CLL), an HIV infection or taking certain drugs after a solid organ transplant.

Merkel cell carcinoma usually starts on areas of skin exposed to the sun, especially the head, neck, arms and legs. It can appear as a firm and raised lump on the skin. The lump can be red, purple or blue and is not usually painful. It grows and spreads quickly (is aggressive), so new lumps may form on nearby skin. Lymph nodes may also become larger than normal, especially in the neck or under the arm. Merkel cell carcinoma often comes back after it's treated (recurs).

The tests used to diagnose Merkel cell carcinoma include:

• a physical exam
• a skin exam
• a skin biopsy, such as a shave biopsy, a punch biopsy or an excisional biopsy ( surgical biopsy)
• a sentinel lymph node biopsy

Staging describes or classifies a cancer based on how much cancer there is in the body and where it is when first diagnosed. This is often called the extent of cancer. The healthcare team uses information from tests to find out the size of the tumour, whether the cancer has spread from where it first started and where the cancer has spread. Doctors use the stage to plan treatment and estimate the outcome (prognosis).

The most common staging system for Merkel cell carcinoma is the TNM system. For Merkel cell carcinoma, there are 5 stages – stage 0 followed by stages 1 to 4. Often the stages 1 to 4 are written as the Roman numerals I, II, III and IV. Generally, the higher the stage number, the larger the cancer is or the more the cancer has spread.

Talk to your doctor if you have questions about staging. Find out more about staging cancer.

The cancer is only in the top or outer layer of the skin (epidermis).

The cancer is 2 cm or smaller.

The cancer is larger than 2 cm.

The cancer has spread to nearby bone, muscle, cartilage or fascia (connective tissue that wraps around muscles, nerves, blood vessels and organs).

There are areas of cancer between where the cancer started (primary site) and the regional (nearby) lymph nodes (called in-transit metastasis). It may also have spread to the regional lymph nodes.

The cancer has spread to other parts of the body (called distant metastasis), such as the lungs, the brain, bone, the liver, distant lymph nodes or skin. This is also called metastatic cancer.

Recurrent Merkel cell carcinoma means that the cancer has come back after it has been treated.

If it comes back in the same place that the cancer first started, it’s called local recurrence. If it comes back in tissues or lymph nodes close to where it first started, it’s called regional recurrence.

It can also recur in another part of the body. This is called distant recurrence.

The following are treatment options for Merkel cell carcinoma. Your healthcare team will suggest treatments based on your needs and work with you to develop a treatment plan.

The type of surgery done depends on the stage.

A wide local excision removes the cancer along with some normal tissue around it (called the surgical margin). It is the standard type of surgery used when the Merkel cell carcinoma is only in the skin and has not spread to other parts of the body.

Mohs surgery removes the cancer in layers, little by little, until no cancer remains. It may be done when surgeons want to leave as much normal tissue as possible (called tissue sparing). Mohs surgery may be done for Merkel cell carcinoma on the face.

A lymph node dissection removes lymph nodes that may contain cancer. It is done when the doctor can feel enlarged lymph nodes or the sentinel lymph node biopsy shows that the sentinel lymph node contains cancer. A lymph node dissection is done after the main tumour has been removed.

Find out more about surgery for non-melanoma skin cancer.

Radiation therapy uses high-energy rays or particles to destroy cancer cells. It is often directed toward nearby lymph nodes or the area where lymph nodes were removed. You may have radiation therapy to:

• destroy any remaining cancer cells left behind after surgery and reduce the risk of the cancer recurring (called adjuvant therapy)
• treat the cancer if surgery can't be done
• treat Merkel cell carcinoma that has come back after surgery
• relieve symptoms of advanced Merkel cell carcinoma (called palliative therapy)

Find out more about radiation therapy for non-melanoma skin cancer.

Drug therapy uses drugs such as chemotherapy or immunotherapy to treat stage 4 or recurrent Merkel cell carcinoma. Drug therapy is used to help shrink the cancer, slow the growth and spread of the cancer and to relieve symptoms of advanced cancer.

The most common drugs offered are:

• avelumab (Bavencio)
• cisplatin, alone or in combination with etoposide
• carboplatin, alone or in combination with etopside
• topotecan
• pembrolizumab (Keytruda)
• retifanlimab (Zynyz)
• nivolumab (Opdivo)

Some of these drugs may not be available in all areas or covered by all provincial or territorial health plans.

Find out more about drug therapy for non-melanoma skin cancer.

Talk to your doctor about clinical trials open to people with skin cancer in Canada. Clinical trials look at new ways to prevent, find and treat cancer. Find out more about clinical trials.

Follow-up care lets your healthcare team keep track of your health for a period of time after treatment ends. This important part of cancer care is often shared among the cancer specialists and your family doctor. They will help you recover from treatment side effects and monitor you for any signs that the cancer has recurred.

Follow-up visits for Merkel cell carcinoma are usually scheduled:

• every 3 to 6 months for 2 to 3 years
• every 6 to 12 months after 3 years

During a follow-up visit, you will have a physical exam and a skin exam. Your doctor will also feel the lymph nodes to see if they are larger than normal.

If the cancer has come back, you and your healthcare team will discuss your treatment and care.