Twenty-three patients with recurrent or persistent epidermoid carcinoma of the oral cavity, all of whom had failed primary antitumor therapy, were treated with interstitial irradiation and a radiosensitizer. Such primary therapy had included radical surgery, external radiation therapy, or a combination of both. All patients underwent afterloading interstitial iridium-192 implants. Each subject received 6 g/m2 metronidazole administered orally in one dose every 48 hours for the duration of the implant. The radiation dose ranged between 4500 and 6500 rads in 65 to 120 hours. Sixteen of 23 patients (69.6%) demonstrated complete regression of local disease, usually within 12 weeks. Ten of the 23 individuals (43%) remain alive and disease-free with an average follow-up of 25 months since the completion of the regimen. Neurologic and hepatic toxicity were notably absent. Nausea, mild diarrhea and accentuation of the radiation-induced mucositis constituted the principal side effects.
Cancer 48:43-47. 1981.
H E SUCCESSFUL CONTROL of solid tumors with
T ionizing irradiation has been limited for several reasons. Hematogenous spread often exists at the initiation of radiotherapy. The tolerance of normal tissue to irradiation, when adjacent to the tumor, rarely exceeds 4000-6000 rads over a four-to six-week period of time. Efforts to overcome this problem have been attempted with the use of iodine-125 and iridium-192 implants.*" However, the major reason for radiation failure is related to new growth of tumor at the primary site from more resistant cancer cells which have survived the erstwhile lethal action of radiation treatment. This is felt to represent the most important factor in the poor local control achieved with the irradiation of certain tumors, principally some central nervous system malignancies and head and neck carcinomas. 11,12 Large variations in the radiosensitivity of cells present in any given malignancy will occur because of differences in the concentration of available oxygen present at the