Radiation therapy for cancer of unknown primary

Radiation therapy uses high-energy rays or particles to destroy cancer cells. It is used to treat some types of cancer of unknown primary (CUP). Your healthcare team will consider your personal needs to plan the type and amount of radiation, and when and how it is given. You may also receive other treatments.

Radiation therapy is given for different reasons. You may have radiation therapy to:

  • destroy the cancer cells in the body
  • destroy cancer cells left behind after surgery or chemotherapy (called adjuvant therapy)
  • relieve pain or control the symptoms of advanced CUP (called palliative therapy)

How radiation therapy is used

Radiation therapy may be used for the following types of CUP or for CUP in certain parts of the body.

Squamous cell CUP in lymph nodes in the neck or groin may be treated with radiation therapy. It may be used as the main treatment, or it may be given after surgery to remove the lymph nodes that have cancer in them. Sometimes radiation therapy is combined with chemotherapy to treat squamous cell CUP in lymph nodes in the neck. This is called chemoradiation. The 2 treatments are given during the same time period.

Adenocarcinoma of unknown primary in lymph nodes under a woman’s arm may be treated with radiation therapy. Doctors will also treat the breast on the same side of the body as the lymph nodes with cancer. Radiation therapy may be given after surgery to remove the lymph nodes and the breast.

CUP in a bone may be treated with radiation therapy. It is used to shrink the tumour and to reduce pain.

A single CUP tumour may be treated with radiation therapy. It may be given after surgery to remove the tumour, or it may be used as the main treatment.

External beam radiation therapy

The type of radiation therapy used most often to treat CUP is called external beam radiation therapy. During external beam radiation therapy, a machine directs radiation through the skin to the tumour and some of the tissue around it.

Side effects

Side effects can happen with any type of treatment for CUP, but everyone’s experience is different. Some people have many side effects. Other people have few or none at all.

During radiation therapy, the healthcare team protects healthy cells in the treatment area as much as possible. But damage to these healthy cells can happen and may cause side effects. Side effects can happen any time during, immediately after or a few days or weeks after radiation therapy. Sometimes late side effects develop months or years after radiation therapy. Most side effects go away on their own or can be treated, but some side effects may last a long time or become permanent.

Side effects of radiation therapy will depend mainly on the size of the area being treated, the specific area or organs being treated, the total dose of radiation and the treatment schedule. Some common side effects of radiation therapy for CUP are:

Radiation to the head and neck can also cause:

Tell your healthcare team if you have these side effects or others you think might be from radiation therapy. The sooner you tell them of any problems, the sooner they can suggest ways to help you deal with them.

Questions to ask about radiation therapy

Find out more about radiation therapy and side effects of radiation therapy. To make the decisions that are right for you, ask your healthcare team questions about radiation therapy.

Expert review and references

  • American Cancer Society. Cancer - Unknown Primary. Atlanta, GA: 2014: http://www.cancer.org/acs/groups/cid/documents/webcontent/003092-pdf.pdf.
  • Fizazi K, Greco FA, Pavlidis N, et al . Cancers of unknown primary site: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Annals of Oncology. Oxford University Press; 2011.
  • Greco FA & Hainsworth JD . Cancer of unknown primary site. DeVita VT Jr, Lawrence TS, & Rosenberg SA. Cancer: Principles & Practice of Oncology. 10th ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2015: 113:1720-1737.
  • Kim KW, Krajewski, KM, Jagannathan JP, et al . Cancer of unknown primary sites: what radiologists need to know and what oncologists want to know. AJR: American Journal of Roentgenology. The American Roentgen Ray Society; 2013.
  • Macmillan Cancer Support. Cancer of unknown primary (CUP). London, UK: Macmillan Cancer Support; 2014: http://www.macmillan.org.uk/Cancerinformation/Cancertypes/Unknownprimary/Unknownprimary.aspx.
  • National Comprehensive Cancer Network. Occult Primary (Cancer of Unknown Primary [CUP]) (Version 3.2014). http://www.nccn.org/professionals/physician_gls/pdf/occult.pdf.