FRACTIONATED HIGH-DOSE-RATE AND PULSED-DOSE-RATE BRACHYTHERAPY - FIRST CLINICAL-EXPERIENCE IN SQUAMOUS-CELL CARCINOMA OF THE TONSILLAR FOSSA AND SOFT PALATE

Purpose: Fractionated high-dose-rate (fr.HDR) and pulsed-dose-rate (PD R) brachytherapy (BT) regimens, which simulate classical continuous lo w dose-rate (LDR) interstitial radiation therapy (IRT) schedules, have been developed for clinical use. This article reports the initial res ults using these novel schedules in squamous cell carcinoma (SCC) of t he tonsillar fossa (TF) and/or soft palate (SP). Methods and Materials : Between 1990 and 1994, 38 patients with TF and SP tumors (5 T1, 22 T 2, 10 T3, and 1 T4) were treated by fr.HDR or PDR brachytherapy, eithe r alone or in combination with external irradiation (ERT). Half of the patients were treated with fr.HDR, which entailed twice-daily fractio ns of greater than or equal to 3 Gy. The other 19 patients were admini stered PDR, which consisted of pulses of less than or equal to 2 Gy de livered 4-8 times/day. The median cumulative dose of IRT +/- ERT serie s was 66 Gy (range 55-73). The results in these patients treated by br achytherapy were compared to 72 patients with similar tumors treated i n our institute with curative intent, using ERT alone. The median cumu lative dose of ERT-only series was 70 Gy (range 40-77). Results: Excel lent locoregional control was achieved with the use of IRT +/- ERT, wi th only 13% (5 of 38) developing local failure, and salvage surgery be ing possible in three of the latter (60%). Neither BT scheme (fr.HDR v s. PDR) nor tumor site (TF vs. SP) significantly influenced local cont rol rates. The type and severity of the side effects observed are comp arable to those reported in the literature for LDR-IRT. These results contrast sharply with our ERT-only series, in which 39% of patients (2 8 of 72) developed local failure, with surgical salvage being possible only in three patients (11%). Taking the data set of 110 patients, in a univariate analysis IRT, T stage, N stage, overall treatment time ( OTT), and BEDcor(10) (biological effective dose with a correction for the OTT) were significant prognostic factors for local relapse-free su rvival(LRFS) and overall survival(OS) at 3 years. Using Cox proportion al hazard analysis, only T stage and BEDcor(10) remained significant f or LRFS (p < 0.001 and 0.008, respectively), as well as for OS (p < 0. 001 and 0.003, respectively). With regard to the current (IRT) and his torical (ERT) series, for the LRFS at 3 years, dose-response relations hips were established, significant, however, only for the BEDcor(10) ( p = 0.03). Conclusion: The 3-year LRFS of approximately 90% for TF and SP tumors reported here is comparable with the best results in the li terature, particularly given the fact that 30% of the patients (11 of 38) presented with T3/4 tumors. When compared with our historical (ERT -only) controls, the patients treated with IRT had superior local cont rol. A dose-response relationship was established for the BEDcor(10). (C) 1997 Published by Elsevier Science Inc.