Introduction to Radiation Oncology
Side Effects of Radiation

Side Effects of Radiation


The side effects of radiation depend on the location and nature of treatment and can very considerably from person to person. For example radiation to the lung can cause pneumonitis or fibrosis.


Side effects may occur early in the course of treatment. These acute side effects tend to resolve over weeks or months. Late side effects can occur after months or years and are usually permanent.


Most common side effects:

  • fatigue (can increase as treatment progresses)

  • skin changes (red, itchy, flaky, hair loss, decrease in perspiration...)

  • nausea +/- vomiting (often 2-6 hours after treatment, can take antiemetic 1/2 - 1 hour prior to treatment)

  • anorexia

  • diarrhea (radiation enteritis can occur once treatment has been underway for a number of weeks)


Radiation causes reproductive cell death, therefore, the time of appearance of radiation injury is influenced by the growth characteristics of the tumour or tissue irradiated. Rapidly growing tumours (lymphoma) show a quick response and slowly growing tumours (prostate) show slow regression.  Likewise, rapidly proliferating normal tissue (mucosa) shows early reaction and slowly proliferating normal tissue (spinal cord) shows late reaction to treatment.