Hyperthermia promotes the incidence of tumours following X-irradiation of the rat cervical cord region

The cervical region of the rat, including the spinal cord (cervical 5-thoracic 2) was irradiated with single doses of 15-32 Gy 250kV X-rays. Hyperthermia, at temperatures of 42-, 43- and 44 ± 0.1oC for 30 min was applied to the cervical vertebral column and immediate adjacent tissues for 5-10 min or 7h after X-irradiation. Over a period of 18-21 months, animals were followed up to monitor neurological complications occurring as a result of damage to the spinal cord (Sminia et al. 1991). The authors also noted the development of neoplasms either inside or outside the cervical region. The data on tumour incidence were analysed retrospectively using the actuarial method. Although hyperthermia alone was not carcinogenic, it led to a significant increase of radiation-induced tumours. (author)