Treating Merkel Cell Carcinoma Based on the Extent of the Cancer

Merkel cell carcinoma (MCC) is rare, so it has been hard for doctors to study how best to treat this cancer. Some doctors might suggest treatments other than those listed here.

Treatment depends mainly on how far the cancer has spread , so having the right tests done to determine the extent of the cancer (such as a sentinel lymph node biopsy or imaging tests like CT, MRI, or PET/CT scans) is very important.

Other factors, such as the location of the tumor and your age and overall health, might also affect your treatment options.

MCC with no obvious spread to the lymph nodes (or elsewhere)

These cancers are thought to be confined to the skin based on physical exams and imaging tests. Once MCC has been diagnosed, a sentinel lymph biopsy (SLNB) is usually done first to see if small amounts of cancer have reached the nodes.

After the SLNB, surgery (usually wide local excision) is done on the skin to try to remove all of the cancer. If the cancer is in a place where it would be hard to remove it with a wide margin (edge) of normal skin, Mohs micrographic surgery might be used. Radiation therapy might be another option instead of surgery for some people.

Within a few weeks after surgery, radiation might be given to the site where the tumor was removed. This is more likely if the doctor thinks there’s a higher risk of the cancer coming back (such as if the main tumor was large, or if the doctor isn't sure if it was all removed).

If a SLNB was done and did not find any cancer in the lymph nodes, some doctors might suggest watching you closely with no further treatment, especially if the main tumor was small and did not have any concerning features. But because MCC often spreads to the lymph nodes, many doctors prefer to give radiation therapy to the nodes to be safe. Radiation to the nodes is also likely to be recommended if SLNB was not done, or if it was done but the results were not clear. (If radiation therapy is being given to the main tumor, the radiation to the lymph nodes is typically given at the same time.)

MCC that has spread to nearby lymph nodes

These cancers have spread to the nearby lymph nodes, which has been confirmed either with a SLNB or with another type of biopsy.

After the biopsy, the main tumor on the skin is treated with surgery (usually wide local excision) to try to remove all of the cancer. If the cancer is in a place where removing it with a wide margin of normal skin would be difficult, Mohs micrographic surgery might be used.

Within a few weeks after surgery, radiation therapy is often given to the site where the tumor was removed, especially if the doctor thinks there is a higher risk of the cancer coming back (such as if the main tumor was large, or if the doctor is not sure if it was all removed).

Lymph nodes that contain cancer cells need to be treated as well. Options might include lymph node dissection to remove them, radiation therapy, or lymph node dissection followed by radiation therapy. (If radiation therapy is being given to the main tumor, the radiation to the lymph nodes is typically given at the same time.) Some doctors might also recommend chemotherapy to try to lower the chances of the cancer coming back, but it’s not clear how helpful this is.

MCC that has spread to other parts of the body

If MCC has spread to other parts of the body, treatment can often help control the cancer and ease symptoms, but these cancers are very hard to get rid of completely. Not all doctors agree on the best way to treat these cancers, so if time permits it’s often a good idea to get a second opinion from a team of experts.

Treatment options might include surgery, radiation therapy, chemotherapy, immunotherapy, or some combination of these. The benefits of each treatment need to be weighed against the side effects they might cause. Be sure you understand the goal of each treatment and its possible downsides before starting treatment.

MCC often shrinks in response to chemotherapy at first, but almost always starts growing again at some point. Chemotherapy can also have side effects that need to be taken into account.

Treatment with one of the immunotherapy drugs known as checkpoint inhibitors might be another option. These types of drugs can shrink some MCC tumors and tend to have fewer side effects than standard chemo, although sometimes the side effects from these drugs can be serious.

Because these cancers can be very hard to treat with current therapies, people with MCC may want to think about taking part in a clinical trial. Studies are now looking at new drugs and combinations of different types of treatments. (See What’s New in Merkel Cell Carcinoma Research? )

MCC that comes back (recurs) after initial treatment

If MCC comes back after treatment, further treatment depends on where it comes back and what types of treatment were used before.

If the cancer comes back on the skin where it first started, surgery (with wider margins) can often be done to try to remove it. This might be followed by radiation therapy to the area if it hasn’t been given before. If the nearby lymph nodes haven't been treated, they might be removed and/or treated with radiation. Some doctors might consider giving chemotherapy as well, but it’s not clear how helpful this might be.

If the cancer comes back in the nearby lymph nodes and they have not been treated before, they might be removed and/or treated with radiation. Some doctors might consider giving chemotherapy too, but, again, it’s not clear how helpful this is.

Cancers that come back in distant parts of the body can be hard to treat. Surgery and/or radiation therapy might be used, but the goal is usually to ease symptoms rather than try to cure the cancer. Chemotherapy can often shrink or slow the growth of the cancer for a time and can help relieve symptoms. But chemotherapy can also cause side effects that need to be taken into account. Treatment with an immunotherapy drug might be another option. These drugs have been shown to be helpful against some advanced MCCs. 

The benefits of each treatment need to be weighed against the side effects they might cause. Be sure you understand the goal of each treatment and its possible downsides before starting treatment.

Because these cancers can be hard to treat, people with MCC might want to think about taking part in a clinical trial. Studies are now looking at new drugs and combinations of different types of treatments (see What’s New in Merkel Cell Carcinoma Research?).