Intracavitary brachytherapy significantly enhances local control of early T-stage nasopharyngeal carcinoma: The existence of a dose-tumor-control relationship above conventional tumoricidal dose

Purpose: To study the efficacy of intracavitary brachytherapy (ICT) in earl y T-stage nasopharyngeal carcinoma (NPC). Methods and Materials: All T1 and T2 (nasal infiltration) NPC treated with a curative intent from 1984 to 1996 were analyzed (n = 509), One hundred si xty-three patients were given ICT after radical external radiotherapy (ERT) (Group A). They were compared with 346 patients treated by ERT alone (Grou p B), The ERT delivered the tumoricidal dose (uncorrected BED-10 greater th an or equal to 75 Gy) to the primary tumor and did not differ between the t wo groups in technique or dosage. The ICT delivered a dose of 18-24 Gy in 3 fractions over 15 days to a point 1 cm perpendicular to the midpoint of th e plane of the sources, ICT was used to treat local persistence diagnosed a t 4-6 weeks after ERT (n = 101) or as an adjuvant for the complete responde rs to ERT (n = 62). Results: The two groups did not differ in patients' age or sex, rate of dis tant metastasis, rate of regional failure, overall survival, or the follow- up duration. However, Group A had significantly more T2 lesions and Group B had significantly more advanced N-stages, Local failure was significantly less (crude rates 6.75% vs. 13.0%; 5-year actuarial rates 5.40% vs. 10.3%) and the disease-specific mortality was significantly lower (crude rates 14. 1% vs. 21.7%; 5-year actuarial rates 11.9% vs. 16.4%) in Group A compared t o Group B, Multivariate analysis showed that the ICT was the only significa nt prognostic factor predictive for fewer local failures (Cox regression p = 0.0328, risk ratio = 0.49, 95% confidence interval (95% CI) = 0.256-0.957 ). However, when ICT was excluded from the Cox regression model, the total physical dose or the total BED-10 uncorrected for tumor repopulation during the period of radiotherapy became significant in predicting ultimate local failure rate. The two groups were comparable in the incidence rates of eac h individual chronic radiation complication and the actuarial cumulative ra te of the chronic radiation complications, with the exception of chronic ra diation nasopharyngeal ulceration/necrosis which occurred in 10 patients in Group A and 1 patient in Group B, Headache (n = 4) and foul smell (n = 8) consequential to ulceration/necrosis were mild and manageable by conservati ve means. A significant dose-tumor-control relationship existed when local failure was studied as a function of the total physical dose or the total b iological equivalent dose (linear quadratic equation, alpha/beta = 10) unco rrected for tumor repopulation during the time course of the radiotherapy. Conclusions: Supplementing ERT which delivered tumoricidal dose (uncorrecte d BED-10 greater than or equal to 75 Gy), ICT significantly enhanced ultima te local control and avoided the necessity for morbid salvage treatments in early T-stage (T1/T2 nasal infiltration) NPC, The slight increase in chron ic radiation ulceration/necrosis after ICT was acceptable with mild and man ageable symptoms, Other late complications were not increased. A significan t dose-tumor-control relationship exists above the conventional tumoricidal dose level. (C) 2000 Elsevier Science Inc.