If you are receiving radiation therapy for a cancer of the head or neck, you may be at risk of a complication called fibrosis. Fibrosis can have a major effect on your oral health. Here are six things that radiation patients need to know about fibrosis. What is fibrosis? Fibrosis is a condition that is characterized by the formation of excess connective tissue. The excess connective tissue destroys the normal function of the affected tissues and makes the affected tissues less elastic.