Radiation for cancer of unknown primary

Radiation therapy is the use of high energy rays (such as x-rays) to kill cancer cells or shrink tumors. The radiation may come from outside the body (external radiation) or from radioactive “seeds” placed right into the tumor (also called internal radiation or brachytherapy). External radiation can be given in the same way as the type of x-ray used to find a broken bone, but it takes longer.

Sometimes both internal and external beam radiation treatment are used at the same time. Radiation might be used with the goal of curing some cancers that have not spread too far from where they started. Even when the cancer has spread too far to be cured by radiation, it can still be used to relieve symptoms such as pain, bleeding, trouble swallowing, or other problems.

Side effects can vary from patient to patient and depend on the radiation dose and the part of the body being treated. Some of the common side effects are:

• Fatigue (feeling tired)
• Loss of appetite
• Low blood counts
• Skin changes like sunburn
• Hair loss at the treatment area (with external beam radiation)

Treatment of certain areas can also have other side effects. For example, radiation to the head and neck area can cause mouth sores and trouble swallowing. Radiation to the abdomen (belly) can cause nausea, vomiting, and diarrhea.

Most of these side effects get better after treatment ends, but some are long-term and may never go away completely. If chemotherapy is given along with radiation, the side effects are often worse.

If you have problems with side effects, you should talk with your doctor or nurse as there are often ways to help. To learn more about radiation treatment, see our document, Understanding Radiation Therapy: A Guide for Patients and Families.