Merkel Cell Carcinoma: Staging and Treatment

What is staging for cancer?

Staging is a way to find out how much cancer is in your body and what treatment can be used. Staging looks at the size of the tumor, where it is, and if it has spread to other organs. Tests like biopsies, CTs, and MRIs may be done to help stage your cancer. Your providers need to know about your cancer and your health so that they can plan the best treatment for you. 

How is Merkel cell carcinoma (MCC) staged?

MCC is staged using the TNM system and the pathological staging system. The staging system is very complex.  

 As described by the American Joint Committee on Cancer, the TNM system has three parts:

• T-Describes the size/location/extent of the tumor.
• N-Describes if the cancer has spread to the lymph nodes.
• M-Describes if the cancer has spread to other organs (metastasized). 

Your healthcare provider will use the results of the tests you had to determine your TNM result and combine these to get a stage from 0 to IV (0 to 4). 

The pathological staging system (also called surgical staging) is used when tissue is removed during surgery and tested. If surgery has not been done, a clinical stage can be given using results from a physical exam, biopsy, and imaging tests.  Below is a summary of the pathological staging system.

• Stage 0 (Tis, N0, M0): The cancer is only in the outermost layer of skin called the epidermis. It has not spread to the lymph nodes or other parts of the body. It is also called carcinoma in situ (Tis). 
• Stage I (T1, N0, M0): The cancer is no more than 2 centimeters (cm) across and has not spread to nearby lymph nodes or distant sites. 
• Stage IIA (T2 or T3, N0, M0): The cancer is between 2 and 5cm across (T2) or more than 5cm across (T3) and has not spread to lymph nodes or other parts of the body. 
• Stage IIB (T4, N0, M0): The cancer has grown into nearby muscle, bone, or cartilage but has not spread to nearby lymph nodes or distant parts of the body. 
• Stage IIIA (T1/T2/T3/T4, N1a(sn)/N1a, M0): The cancer is any size and may have grown into nearby tissues. It has also spread to nearby lymph nodes found during a lymph node biopsy or surgery and was not seen on exams or imaging tests. It has not spread to distant parts of the body. 
• Stage IIIA (T0, N1b, M0): There is no sign of primary cancer and it has spread to nearby lymph nodes that were seen on exam or imaging tests and confirmed by biopsy or surgery. It has not spread to distant sites. 
• Stage IIIB (T1/T2/T3/T4, N1b/N2/N3, M0): The cancer is any size and may have grown into nearby tissues. It has not spread to distant sites. It also must meet any of these criteria:
  • Spread to nearby lymph nodes (seen on exams or imaging tests and confirmed with a biopsy or surgery).
  • Spread toward nearby lymph node areas without reaching the lymph nodes.
  • Spread toward a nearby lymph node area and has reached the nodes. 
• Stage IV (T0/T1/T2/T3/T4, Any N, M1): The cancer is any size and may have grown into nearby tissues. It may or may not be in the nearby lymph nodes. It has spread to distant lymph nodes or organs. 

Talk to your provider about the stage of your cancer.

How is MCC treated?

Treatment for MCC depends on things like your cancer stage, age, overall health, and testing results. Your treatment may include:

• Surgery.
• Chemotherapy.
• Radiation Therapy.
• Immunotherapy.
• Clinical Trials.

Surgery

Surgery is the main treatment for MCC. It can be done to diagnose MCC and to see if it has spread. A skin biopsy is often done before your provider thinks you have MCC. A small part of the lesion is removed and tested to see what kind of cells it is made of. A sentinel lymph node biopsy will likely be done to help figure out the stage of your cancer. Once your diagnosis is confirmed, you will have surgery to remove the cancer and likely some extra tissue around the cancer.

If cancer is found in your lymph nodes, a lymph node dissection will be done to remove other nearby lymph nodes. In some cases, a Mohs procedure is done to remove the lesion. During a Mohs procedure, thin layers of skin including the tumor are removed, frozen, and looked at under a microscope. This is repeated until the layer of skin removed shows no cancer. The amount of tissue that needs to be removed may be large, and you might not have enough healthy tissue to heal. If this is the case, you may need skin grafts and reconstructive surgery. Your surgeon will talk to you about your options for surgery. 

Chemotherapy

Chemotherapy is the use of anti-cancer medicines that go through your whole body. MCC is rare so it is hard to know which medications work best. Chemotherapy is most likely helpful for MCC that has spread to other parts of the body.  The most common chemotherapies used for MCC are cisplatin, carboplatin, etoposide, and topotecan. Your care team will talk to you about which chemotherapy regimen is best for you. 

Radiation

Radiation therapy is the use of high-energy x-rays to kill cancer cells. Radiation therapy tends to work well for MCC, but there is question about when it's best to get radiation. Radiation can be used:

• After surgery to kill any leftover cancer cells. 
• To treat the cancer if surgery is not an option. 
• To treat the lymph nodes near the main tumor. 
• As treatment of MCC that has recurred (come back) after surgery. 
• To treat MCC that has spread to other parts of the body (metastasis). 

Your radiation oncologist will talk with you about the best course of treatment for your cancer.

Immunotherapy

Immunotherapy is the use of medications that stimulate (rev up) the immune system to attack and kill cancer cells. Immunotherapy for MMC is given intravenously (IV, into a vein) and can shrink the cancer or slow down its growth. Common immunotherapy medications used to treat MMC are:

• Avelumab: Blocks PD-L1, a protein that is found on some MCC cells.
• Pembrolizumab and Nivolumab: Block PD-1, a protein found on some MCC cells.

Clinical Trials

You may be offered a clinical trial as part of your treatment plan. To find out more about current clinical trials, visit the OncoLink Clinical Trials Matching Service.

Making Treatment Decisions

Your care team will make sure you are part of choosing your treatment plan. This can be overwhelming as you may be given a few options to choose from. It feels like an emergency, but you can take a few weeks to meet with different providers and think about your options and what is best for you. This is a personal decision. Friends and family can help you talk through the options and the pros and cons of each, but they cannot make the decision for you. You need to be comfortable with your decision – this will help you move on to the next steps. If you ever have any questions or concerns, be sure to call your team.