ESTRO 2022 - Abstract Book

S539

Abstract book

ESTRO 2022

Purpose or Objective The recommended treatments for basal cell carcinoma (BCC) in the head and neck (H&N) region are Mohs surgery, standard surgical excision, and radiotherapy. According to the available literature, the local recurrence after primary surgical treatment in this area is associated with a worse prognosis in the case of re-treatment. To our knowledge, there are no scientific reports on the results of treating only the BCC of the H&N region by high-dose brachytherapy (HDR-BT), both in the case of primary lesions and relapses after previous standard surgical excision. The aim of this study is to fill this gap in the literature. Materials and Methods Between 03.2012 and 02.2017 a total number of 510 patients with diagnosed skin neoplasms were treated with different techniques, dose rates, and schedules of BT. The clinical inclusion criteria for this study were pathologically confirmed BCC, tumor location in the H&N region, treatment performed with superficial HDR-BT in 2D planning using the 10 x 5 Gy fractionation scheme, and a minimum follow-up of 12 months from the end of treatment. A retrospective analysis was performed on a group of 90 patients in whom a total of 102 tumors were treated. Subsequently, tumors were divided into two subgroups - those treated initially with HDR-BT and treated with this method due to local recurrence after previous standard surgical excision. The primary treatment group included 59 tumors (47 T1 and 12 T2). Whereas 43 tumors were included in the recurrent group (35 T1 and 8 T2). Early skin toxicity was assessed 4 weeks after the treatment, then every 3-6 months the late toxicity was evaluated (using the RTOG scale). Results Statistical analysis didn’t reveal any significant differences between the groups in terms of age (both medians 72.9 y, p=0.43), duration of treatment (both medians 11 d, p=0.17), follow-up time (median 41.4 m vs. 43.5 m, p=0.96), sex (p=0.18), local advancement (p=0.83) and location (p=0.68). The Kaplan-Meier-estimated 5-year relapse-free survival was 96.4% in the primary group and 94.6% in the recurrent group. Using the log-rank test, no statistically significant difference was found in the number of recurrences in both groups (p=0.72). In the primary group toxicity presented as follows: early G1-20.3%, G2-28.8%, G3-42.4%, G4-8.5%; late G1-33.9%, G2-50.8%, G3-1.7%, G4-11.9%. Whereas, in the recurrent group toxicity presented as follows: early G1-16.3%, G2-41.9%, G3-37.2%, G4-4.6%; late G1-30.2%, G2-62.8%, G3 - 4.6%. There were no statistically significant differences in the early nor late toxicity between the groups (p=0.54 and p=0.16). The analysis of factors influencing the increased toxicity showed higher degrees of late complications after the treatment of T2 tumors (p=0.028). Conclusion Superficial 2D HDR-BT in the presented fractionation scheme is a highly effective treatment method for both primary and recurrent BCC after standard surgical excision of the H&N region and is associated with acceptable early and late skin toxicity. 1 National Institute of Oncology, Centre of Radiotherapy (Semmelweis University, Department of Oncology), Budapest, Hungary; 2 National Institute Of Oncology, Centre of Radiotherapy, Budapest, Hungary; 3 Osaka Dental University, Department of Oral Radiology, Osaka, Japan; 4 National Institute of Oncology, Centre of Radiotherapy, Budapest, Hungary; 5 National Institute of Oncology, Multidisciplinary Centre of Head and Neck Tumours, Budapest, Hungary Purpose or Objective To describe the results of treating tongue cancer patients with single postoperative interstitial, high-dose-rate (HDR) brachytherapy (BT) after resection. Materials and Methods Between January 1998 and April 2019, 47 patients with squamous cell histology, stage T1-3N1M0 tongue tumours were treated by surgery followed by a single HDR BT in case of negative prognostic factors (close or positive surgical margin, lymphovascular and/or perineural invasion). The average dose was 29.6 Gy (range: 10-45 Gy) and rigid metal needles were used in 11 (23%) and flexible plastic catheters in 36 cases (77%). The survival parameters and toxicities were analysed and also the prognostic factors influencing survival. Results During a mean follow-up of 96 months (range: 16-260 months) for surviving patients, the probability of 10-year local and regional control (LC, RC), overall survival (OS), and disease-specific survival (DSS) was 86%, 73%, 35% and 64%, respectively. The incidence of local grade 1, 2 and 3 mucositis was 21%, 75% and 4%, respectively. As a serious (grade 4), late side effect, soft tissue necrosis developed in 3 cases (6%). In a univariate analysis, there was a significant correlation between lymphovascular invasion and RC (p=0.023) as well as cervical recurrence and DSS (p ˂ 0.0001). Conclusion Sole postoperative HDR brachytherapy can be an effective method in case of negative prognostic factors in the treatment of early, resectable tongue tumours. Comparing the results of patients treated with postoperative BT to those who were managed with surgery or BT alone known from the literature, a slightly more favourable LC can be achieved with the combination therapy, demonstrating the potential compensating effect of BT on adverse prognostic factors, while the developing severe, grade 4 toxicity rate remains low. OC-0615 Results of sole postoperative interstitial, high-dose-rate brachytherapy of tongue tumours Z. Takacsi-Nagy 1 , O. Ferenczi 2 , T. Major 1 , H. Akiyama 3 , G. Frohlich 4 , F. Oberna 5 , M. Revesz 5 , M. Poosz 4 , C. Polgar 1