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Radiation Therapy for Merkel Cell Carcinoma

Radiation therapy uses high-energy rays (like x-rays) or particles (such as electrons) to kill cancer cells. The radiation is focused from outside the body onto the tumor.

When might radiation therapy be used?

Not all doctors agree on exactly when radiation therapy should be used for Merkel cell carcinoma (MCC), but it works very well for MCC. It might be used in these situations:

  • To treat the area of the main (primary) skin tumor after surgery to try to kill any cancer cells that might have been left behind. (You may hear this called adjuvant radiation.) This is especially important if there’s a high chance that the cancer will come back (such as if the main tumor was large, or if the doctor isn't sure it was all taken out).
  • To treat the main tumor if surgery isn't an option, such as if a person isn’t healthy enough for surgery or the tumor is in a place where all of it can't be removed.
  • To treat the lymph nodes near the main tumor. If a sentinel lymph node biopsy (or other type of biopsy) found cancer in the lymph nodes, if the results of the biopsy were not clear, or if a biopsy wasn't done, radiation therapy is often given to the lymph nodes in the area. This might be done after a lymph node dissection , or it might even be done instead of a lymph node dissection.
  • To help treat MCC that has come back (recurred) after surgery, either in the skin or lymph nodes.
  • To help treat MCC that has spread to distant parts of the body, often along with other treatments. In this case, the radiation is used to help shrink or slow the growth of the cancer and/or to help ease symptoms caused by its spread, but it’s not expected to cure the cancer.

How is radiation therapy given?

When used to treat MCC, radiation is usually given 5 days a week for many weeks. The length of treatment might be shorter if the radiation is being used to relieve symptoms caused by cancer spread.

Before treatments start, your radiation team will take careful measurements to decide the proper dose of radiation and know exactly where to aim the radiation beams. This planning session is called simulation.

Getting radiation treatment is a lot like getting an x-ray, but the radiation is stronger and aimed precisely at the cancer. The treatments don't hurt. Each one lasts only a few minutes, though the set-up time – getting you into place for treatment – takes longer.

Possible side effects of radiation therapy

Common side effects depend on where the radiation is aimed and can include:

These often get worse as treatment goes on and slowly go away after treatment ends.

Radiation therapy can also raise the risk of getting another type of cancer in the treated area. If this happens, it’s usually many years after treatment.

More information about radiation therapy

To learn more about how radiation is used to treat cancer, see Radiation Therapy.

To learn about some of the side effects listed here and how to manage them, see Managing Cancer-related Side Effects.

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as editors and translators with extensive experience in medical writing.

Cestaro G, Quarto G, DE Monti M, et al. New and emerging treatments for metastatic Merkel cell carcinoma. Panminerva Med. 2018;60(1):39-40.

National Cancer Institute. Merkel Cell Carcinoma Treatment (PDQ®)–Patient Version. May 2, 2018. Accessed at on August 15, 2018.

National Comprehensive Cancer Network, Clinical Practice Guidelines in Oncology (NCCN Guidelines®), Merkel Cell Carcinoma, Version 2.2018 -- June 15, 2018. Accessed at on August 15, 2018.

Patel P, Modi C, McLellan B, Ohri N. Radiotherapy for inoperable Merkel cell carcinoma: a systematic review and pooled analysis. Dermatol Pract Concept. 2018;8(2):149-157.

Tetzlaff MT, Nagarajan P. Update on Merkel Cell Carcinoma. Head Neck Pathol. 2018;12(1):31-43.  

Last Revised: October 9, 2018

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