PLACE OF IRIDIUM 192 IMPLANTATION IN DEFINITIVE IRRADIATION OF FAUCIAL ARCH SQUAMOUS-CELL CARCINOMAS

Purpose: We have reviewed the results of 165 T1 and T2 squamous cell c arcinomas of the faucial arch treated by definitive irradiation includ ing or not Iridium 192 brachytherapy to ascertain whether a significan t relationship existed between Iridium implantation, local control, co mplications, and survival. Methods and Materials: From March 1971 to N ovember 1990, 58 Tl and 107 T2 (NO: 107/165; N1: 30/165; N2: 9/165; N3 : 19/165) biopsy proven squamous cell carcinomas of the tonsillar regi on (104/165) and the soft palate and uvula (61/165) were treated in He nri Mondor Hospital by definitive irradiation with curative intent. Fr om 1971 to 1981 (period 1), only guide gutter technique was available, so that implants were reserved for small tumors: patients were either managed by definitive telecobaltherapy to tumor site and neck node ar eas (Group 1; n = 48; mean dose: 70 Gy; confidence interval: +/- 5.5; 5 fractions of 1.8 Gy per week) or by exclusive Iridium implant (Group 2; n = 11; all Tl NO; 64 Gy +/- 4.8) or by a combination of external beam radiation therapy to tumor site and neck nodes areas and Iridium implant (Group 3; n = 40). In 1981 (Period 2), a new plastic tube tech nique, which enables implantation of larger areas, was introduced in t he department and all patients (Group 4; n = 66) were then managed by external radiation therapy (Group 3 + 4 : 47 Gy +/- 4.3) followed by a n Iridium implant (31 Gy +/- 10.5). Clinically positive neck nodes eit her received additional external dose with electrons or were excised. Results: Overall 5-year survival (Kaplan Meier) was 21%, 50.5%, and 60 % in groups 1, 2, and 3 + 4, respectively (p < 0.001, log rank). Five- year local control was 58%, 100%, and 91%, respectively (p < 0.001). F ive-year necrosis rate was 4.5%, 20.5% and 18%, respectively (N.S.). C omparison of results between the two periods of the study (Group 1 + 2 + 3 vs. group 4) show that these two groups are statistically compara ble according to site and size of tumor and N status and that both loc al control (77% vs. 94% at 5 years; p < 0.01) and disease-free surviva l (56% vs. 71%; p = 0.03) were improved after 1980, while there was a trend to an increase in overall survival (42% vs. 53% at 5 years; p = 0.08); nodal control (86% vs. 95% at 5 years), and necrosis rate (11% vs. 20% at 5 years) were not modified. Multivariate analysis showed th at both local control (p < 0.0001) and overall survival (p < 0.0001) w ere improved when tumor was implanted. Conclusion: We recommend then t o treat T1 and T2 squamous cell carcinomas of the faucial arch by exte rnal radiation therapy to tumor site and neck areas (45 Gy/25 fraction s/5 weeks) followed by a 30 Gy Iridium implant and, for patients with clinically positive nodes, either a further 25-30 Gy electron beam irr adiation to the nodes or neck node dissection.