General Medical Information

Radiation

David J. Terris

Radiation induces acute, intermediate, and chronic effects on tissues. The acute effects (whose severity is related to the radiation fraction) include a significant reduction in fibroblast, myofibroblast, and endothelial cell proliferation (which may result in impaired wound contraction). The intermediate effects are usually manifested between 3 and 6 months after radiation and result in diminished endothelial and connective tissue proliferation. The late effects (which are related to the total radiation dosage) include hyalinization of collagen, rupture of elastic fibrils, deposition of fibrinous exudate, and induction of atypical fibroblasts. Likewise, blood vessels become hyalinized and sclerotic; this may lead to cerebrovascular disease in patients receiving radiation for head and neck cancer. The optimal time to operate on patients whose tissues have been irradiated is after the acute effects have subsided (no less than 3 weeks) but before the intermediate effects have emerged (no more than 3 months).

The mechanism by which radiation therapy impairs wound healing is not well understood. Although inhibition of fibroblast proliferation has been implicated, there is preliminary evidence to suggest that damage to the resident fibroblasts is not as critical as suppression of the hematopoietic system. Although the net effect is a wound that is slower to heal, a decrease in the wound contraction may be an effect that can be exploited.

Several authors have now examined the impact of combination chemoradiation therapies, so-called organ preservation protocols, on wound healing. Although surgery for salvage in these patients is considered safe and desirable, there is a growing consensus that the risk of wound complications (particularly fistulae and flap necrosis) in this patient population is increased, especially when the pharynx is entered. Of particular concern is the prolonged time to resolution of fistulae and flap necrosis, up to 7.7 months in one study.

Osteoradionecrosis is one manifestation of poor wound healing after radiation. This feared complication of oral cavity radiation is difficult to treat and may require surgery, prolonged courses of intravenous antibiotics, and in some instances hyperbaric oxygen.