Cesium-137 needle brachytherapy boosts after external beam irradiation for locally advanced carcinoma of the tongue and floor of the mouth

PURPOSE: A retrospective study was undertaken to compare local tumor control and complications of external beam radiation therapy with and without interstitial 137Cs needle brachytherapy boost doses. METHODS AND MATERIALS: Two hundred one consecutive patients with locally advanced (T3-T4) cancer of the tongue and floor of the mouth treated with definitive radiotherapy by external beam irradiation with (n = 78) or without (n = 123) low-dose-rate interstitial brachytherapy from 1974 to 1999 were analyzed retrospectively. External beam irradiation was administered with conventional fractionation in 105 patients and administered with accelerated hyperfractionation in 96 patients. RESULTS: The 8-year actuarial local control rates showed a trend toward improved results in the combined-treatment group as a whole and also when it was stratified into patients with base of tongue sites and those with oral tongue and floor of mouth sites. Cox regression analysis for local control showed that the only significant variable was overall treatment time. The use of brachytherapy boost doses was not a significant variable. The 8-year actuarial probability of Radiation Therapy Oncology Group and European Organization for Research and Treatment of Cancer Grades 3-5 late effects was 25% and 35% for patients with and without brachytherapy, respectively (p = not significant), although the crude incidence of mandibular radiation osteonecrosis was 10% and 1.6%, respectively (p =0.001). CONCLUSIONS: This study showed a trend toward improved local control rates for brachytherapy after external beam radiotherapy. The incidence of mandibular osteonecrosis was increased.