Results of brachytherapy for cancer of the tongue with special emphasis on local prognosis.

One hundred and sixty-six patients with squamous cell carcinoma of the tongue were treated with radiation. Treatment modalities were mainly interstitial implant with or without external beam irradiation, except for early lesions, which were treated with intraoral electron beam therapy. Analysis was made on the local prognosis of the lesion to clarify the indications for interstitial therapy, especially the combined program with external beam therapy, and the time-dose relationship of the brachytherapy. Local recurrence-free rates (two years) were 94% in T1, 77% in T2 and 32% in T3 lesions, respectively. For T1 and superficial or exophytic T2 lesions, the local recurrence-free rate was excellent with the interstitial therapy alone using either permanent implants of gold grain or radium implants. Therefore, prior external beam therapy seemed to be unnecessary for these lesions. When the treated area was less than 10 cm2, subsequent complications were not likely even if the TDF (time-dose factor) value was high. Most of the patients who received combined external beam and interstitial therapy showed infiltrative T2 and a majority of the T3 lesions. In these patients, it was apparent that most of the total dose should be given from the interstitial implant after a small prior dose with external irradiation, because these lesions could not be cured even if the external dose was increased.