Purpose: To examine the prognostic factors for lymph node metastasis after brachytherapy for early (T1-T2N0M0) oral tongue cancer.
Methods and materials: We reviewed the records of 571 patients (500 low dose rate and 71 high dose rate) treated at Osaka University Hospital between 1967 and 1999.
Results: Patients with lymph node metastasis had tumor with an average diameter of 26 +/- 8 mm and a thickness of 9 +/- 5 mm; for patients without lymph node metastasis, the corresponding dimensions were 23 +/- 8 mm and 7.5 +/- 4 mm (p = 0.0004 and 0.001, respectively). After 5 years, the ulcerative (48%) and indurative/infiltrative (39%) types showed a higher ratio of nodal involvement than the exophytic (31%) and superficial (19%) types (p <0.0001). Multivariate analysis showed ulceration (p = 0.006) and a thickness of <or =6 mm (p = 0.04) to be statistically significant predisposing factors for lymph node metastasis. The lymph node control rate was 68% in 1967-1979, 71% in 1980-1990, and 66% in 1990-1999; the corresponding successful salvage rates for lymph node metastasis were 43%, 33%, and 58% (p = 0.04).
Conclusion: The appearance of the tumor, especially the presence or absence of ulceration and the diameter and thickness, are useful prognostic indicators for lymph node metastasis. Although the rates of lymph node metastasis did not change, the salvage outcome for recurrence after interstitial radiotherapy has recently improved.