INHIBITION OF SUBSEQUENT NODAL METASTASIS BY LOW DOSE OF ELECTIVE NECK IRRADIATION FOR TONGUE CANCERS

PURPOSE: To study the influence of elective neck irradiation (ENI) with a dose of ≤ 30 Gy on subsequent nodal metastasis for tongue carcinomas. METHODS: Forty-nine patients controlled at the primary site were evaluated. They were treated with interstitial irradiation and ENI of ≤30 Gy from 1979 to 1991. RESULTS: Subsequent nodal metastases developed in 14 patients (29%) 1 to 23 months after radiotherapy. The nodal recurrence rates were 4/10 (40%) for 0 Gy, 4/9 (44%) for 10-15 Gy, 6/22 (27%) for 16-20 Gy, and 0/8 (0%) for 21-30 Gy. The rates according to tumor thickness were 5/28 (18%) for superficial tumors and 9/21 (41%) for deeply invasive tumors. These factors were shown to be significant by multivariate analysis. The nodal recurrence from irradiated fields developed late compared with that from outside the fields. Successful salvage was obtained in 11/14 (79%), depending on the recurrent nodal stage. The five-year survival rate was significantly better in patients with irradiation of >15 Gy (96%) than those with 15 Gy or less (79%). CONCLUSION: ENI of low dose (15-30 Gy) significantly reduced nodal recurrence rate and prolonged survival. An elective dose of 30 Gy including the upper and middle neck was able to reduce subsequent nodal metastases about 10%(from 37% to 27% in our review).