Extended-term effects of head and neck irradiation in a rodent.

Radiotherapy to the head and neck is a common treatment for malignancies of the region. Unfortunately, exposure to irradiation often results in a variety of complications, most of which are localised and expressed in the short term following irradiation. However, prolonged and systemic effects may have greater clinical importance as the survival rate of head and neck irradiated patients is increasing yearly. Six groups of 18-20 rats were evaluated during a 1 year study. The non-irradiated control group was compared with 2.5 Gy, 5, 7.5, 10 and 15 Gy irradiated groups. We found a dose-dependent reduction in both survival and body weight in our rat models following a delayed, prolonged and chronic process. Dying animals were emaciated, dehydrated and starved, and many were blind and immunocompromised. While the exact underlying mechanism of this delayed, but devastating, phenomenon has not yet been determined, the delayed xerostomia inflicted on these animals may, at least partially, explain it. The clinical implications for head and neck patients require further evaluation, but our data should be considered, in the context of the available evidence for the long-term effects of head and neck irradiation in humans.