photo by Rhoda Baer, NCI

Radiotherapy, or radiation, is a common and widely utilized form of cancer treatment. According to the National Cancer Institute, therapy for about half of all cancer patients will include some aspect of radiotherapy 1.

What it's effective for and why

In a nutshell, radiotherapy uses high energy atomic particle waves to damage the DNA of a cell beyond the cell's own ability to repair it, forcing the cell to commit suicide. There are many different types of radiotherapy, but the most common type is external-beam radiation therapy2,  which simply means that the source of the radiation comes from outside ('external') of the body. Other types include brachytherapy (internal radiation) and radioimmunotherapy (a targeted chemotherapy drug delivers radiation to cancer cells in the body).

Radiotherapy side effects: Overview

Some common side effects of radiation treatment, regardless of the radiation field, include hair loss and fatigue. However, in radiotherapy, side effects of treatment are typically divided into early (acute) side effects and late (chronic) side effects3: Early side effects tend to cause problems to areas of fast-growing cells (skin, mucous membranes in the mouth), they begin at or shortly following therapy, and tend to go away over time. Late side effects tend to occur due to severe, irreparable damage to tissues or organs, and they can come on months or years following therapy.


  1. National Cancer Institute: Radiation therapy
  2. American Society of Clinical Oncology: Types of Treatment
  3. Boyiadzis, Michael M. et al. Hematology-Oncology Therapy. 2007. New York: McGraw Hill, Medical Publishing Division.

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