Treatment outcome of high-dose-rate interstitial radiation therapy for patients with stage I and II mobile tongue cancer

Objectives: The aim of the study was to investigate the outcomes of high-dose-rate interstitial radiation therapy for patients with Stage I and II mobile tongue cancer retrospectively. Methods: Sixty-seven patients with Stage I and II mobile tongue cancer were treated with highdose- rate interstitial radiation therapy, with or without external beam radiation therapy, between 1997 and 2007. The median dose of interstitial radiation therapy was 50 Gy in 10 fractions over 6 days. Thirty-five patients received external beam radiation therapy before interstitial radiation therapy. The median dose of external beam radiation therapy was 20 Gy delivered with singlelateral or bilateral fields, including the primary tumor site and upper jugular lymph nodes. Thirtyseven patients received concurrent chemotherapy, including carboplatin, cisplatin, fluorouracil or tegafur, gimeracil and oteracil (TS-1) systemically or with intra-arterial injection. Thirty-three patients received intratumoral injection of bleomycin before catheter insertion. The median follow-up time was 58.6 months (range 15.1-102.4 months). Results: The 5-year overall, cause-specific, progression-free survival rate and local control rate were 88.7, 92.1, 76.0 and 94.0%, respectively. Fourteen patients developed cervical lymph node recurrence, 11 of which were distributed within the external beam radiation therapy field. We found local failures in four cases within 2 years after the treatment and in three cases after 7 years, even though the latter were difficult to distinguish from second primary cancers. Conclusions: The treatment results of our institutions were equivalent to previous reports. Most cervical lymph node metastases occurred within the external beam radiation therapy field, which implied that the external beam radiation therapy dose of 20-30 Gy was insufficient to prevent late cervical lymph node metastases.