Knowledge Base

What are the side effects of radiation therapy?

There are two types of side effects of radiation therapy:

• acute or early side effects or toxicitiesthat appear during the radiation therapy treatment and disappear within 3-6 months after the treatment end;
• late side effects or toxicities that appear more than 6 months after the treatment end and are irreversible.

The side effect intensity and their probability of occurrence vary greatly among patients, and sometimes also in function of the used radiotherapy technique.

Side effects also vary in function of the irradiated area as they only concern the tissues and organs included in the radiation field (unlike chemotherapy that has an effect in the whole body).

Acute side effects mainlyconcern skin and mucous membranes (oral cavity, intestine, bladder, genital mucous membranes). These include, but are not limited to, dermatitis (reddening of the skin), mucositis (similar to mouth ulcers), diarrhea, and increased urination frequency. The radiation oncologist can prescribe drugs The radiation oncologist can prescribe drugs to manage their symptoms during radiotherapy. These side effects progressively decrease and disappearafter the treatment end.

Late side effects are much rarer (less than 10% of all patients who receive radiotherapy), but are sometimes more disabling because they tend to become chronic. They are often difficult to predict and the radiation oncologist has their prevention in mind when preparing the patient’s treatment plan. Examples of late side effects include skin fibrosis, particularly of the breast after radiation therapy for breast cancer, cystitis and radiation proctitis, which can lead to blood in stool and urine after prostate radiation therapy, and radiation necrosis (i.e. damage of the tissue) after radiation therapy to the brain.