Brachytherapy for Oral Tongue Cancer: An Analysis of Treatment Results with Various Biological Markers

Objective: Low-dose-rate (LDR) brachytherapy is an effective treatment for tongue cancer. However, little is known about the biological mechanism underlying this therapy, character-ized by delivery of continuous exposures of LDR irradiation. It is reported that lower micro-vessel density (MVD), lower Ki-67 index or higher expression of endogenous hypoxic markers such as carbonic CA IX and Glut-1 are related to the poor control of tumors treated with external irradiation. To elucidate the biological characteristics of LDR brachytherapy, we analyzed our results in cases of tongue cancer treated with LDR brachytherapy by using immunohistochemical stainings with antibodies against Ki-67 and MVD, Glut-1 and CA IX. Methods: The prognostic value of Ki-67 index, MVD and the expression of CA IX and Glut-1 was assessed in 68 tongue cancers treated with LDR brachytherapy. The specimens were taken from tongue cancers before radiation therapy and immunohistochemical staining was performed. Results: The local recurrence-free survival rates were significantly different between T1þT2 and T3 (P 0.00067), but not between low and high Ki-67 indexes (P 0.54), between low and high MVD (P 0.071), low and high CA IX indexes (P 0.062) or low and high Glut-1 indexes (P 0.107). T stage, the size of the tumor was the only significant factor for local control in multivariate analyses (P 0.0377). Conclusion: LDR could overcome the radioresistence of non-cycling and hypoxic cells; however, we cannot draw firm conclusions due to the limited number of patients. Key words: tongue cancer – brachytherapy – Ki-67 – microvessel density – CA I