For GPs

Side Effects of Radiation Therapy

The side effects of radiation therapy (also called radiotherapy) vary depending on the type of cancer being treated, the area being treated, and the length and purpose of treatment. Side effects can also vary from patient to patient, even for those undergoing the same type of treatment. While some patients report no side effects at all, most people having radiation therapy will have some mild side effects during and/or just after treatment.

Many patients experience fatigue which builds up throughout the treatment period, especially if the treatment course takes several weeks. Depending on the site treated, other common side effects include skin redness and soreness, bowel upset, bladder symptoms, nausea, and sore mouth or throat. There are medications, creams and other measures to help with many of these common side effects.

It is rare that radiation therapy treatment would need to be stopped or someone is admitted to hospital as a result of side effects. Organs and body parts outside the treated area will not be affected by radiation therapy. For example, the skin will not get red and sore if it is away from the area where the radiation is being targeted. Hair will only thin or fall out if the hair is in the area being treated. This means that only patients with cancer in the brain, skull or scalp will experience hair loss on their head.

The majority of side effects disappear completely within a few weeks of finishing radiation therapy. A small number of patients experience more serious and/or long-term side effects.

The treating doctor will discuss these side effects in detail with each person who might be recommended to have radiation therapy. Radiation therapy would only be prescribed if it is agreed that the overall benefits of the treatment outweigh the risk of more serious side effects. As side effects largely depend on the location of the tumour in the body (either the original cancer and/or where the cancer has spread to), it is difficult to generalise about side effects.

Side effects for specific cancer types:

Arteriovenous Malformation 

Lung Cancer 

Skin Cancer and Melanoma

Bladder Cancer 


Stomach Cancer

Brain Cancer 


Thyroid Eye Disease

Breast Cancer

Oesophageal Cancer

Thyroid Cancer

Cervical Cancer

Palliative Treatment

Upper Gastro-Intestinal

Colorectal Cancer 

Pancreatic Cancer

Uterine Cancer

Head and Neck Cancer

Pituitary Adenoma

Vestibular Schwannoma


Prostate Cancer

Liver Cancer 


Page last updated: 10/09/2020