Electron beam radiotherapy for tongue cancer using an intra-oral cone.

To explain the adaptation technique using an intra-oral cone (IOC) for radiation therapy, and to determine the optimal schedule resulting in a high local control rate and an acceptable complication rate using direct electron beam radiation for the treatment of tongue cancer. Thirty patients with the tongue cancer (T1:T2:T3=16:11:3) were treated with 6-15 MeV electron radiation using an IOC. Twenty-six patients were treated with electron radiation using an IOC with or without an excisional biopsy. The other four patients were treated with a combination of the external beam radiation and electron radiation using the IOC. In order to formulate a safe and effective treatment program, we calculated the biologically effective dose (BED). The two- and five-year local control rates for all patients were 63% and 52%, respectively. The two- and five-year overall survival rates for all patients were 73% and 69%, respectively. Local control was achieved in 12 of 15 patients who were irradiated with a BED of 90.9 Gy(10) or more, whereas it was not achieved in nine of the 15 patients who were treated with less than a BED of 90.9 Gy(10) (p=0.03). The application of electron radiation using an IOC for the treatment of tongue cancer provides acceptable local control and adverse effect rates, especially for elderly patients considered to be high risk for complications from anesthesia. The optimum BED(10) value for the treatment of early tongue cancer using the IOC technique appears to be at least 90.9 Gy(10).