ESTRO 2022 - Abstract Book

S1611

Abstract book

ESTRO 2022

(a) selecting region of interest and transferring x,y coordinates into Microsoft Exel; (b) solving quadratic equation gives coordinates of center film blackening

(c) setting a dot into center of film blackening (d) dwell position determination in Oncentra 4.5

Results “Digital method” allows to reconstruct source dwell position with accuracy of 0.1mm, “manual method” – 0.5mm. An example data for ring (60˚ Ø26mm) is presented in Table 1. Table 1. Mean absolute differences from the measured position of the source determined autoradiographically to the Measured Source Path provided by manufacturer for ring (60˚ Ø26mm).

Dwell position, mm Digital (mean± SD), mm Manual (mean± SD), mm 300 0.9±0.7 0.6±0.6 280 0.9±0.6 0.4±0.9 260 0.7±0.5 0.4±0.5 240 1.5±0.3 1.8±0.8

Conclusion Because “digital method” is independent from human sensitivity, it gives an appropriate reproducible result for determination a center of film blackening comparing to “manual method”.

Poster (digital): Brachytherapy: Head and neck, skin, eye

PO-1807 Long-term outcome of high-dose-rate brachytherapy in early stage non-melanoma skin cancer.

J. Quirós Rivero 1 , M. Gonzalez de Dueñas 1 , C. Corral Fernandez 1 , F. Ropero Carmona 1 , B. Baños Perez 1 , F. Garcia Urra 1 , V. Vera Barragan 1 , P. Simon Silva 1 , J.L. Muñoz Garcia 1 , J. Cabrera Rodriguez 1 , Y. Rios Kavadoy 1

1 Hospital Universitario de Badajoz, Radiation Oncology, Badajoz, Spain

Purpose or Objective To analyze the results in terms of overall survival (OS), cancer specific survival (CSS), local control (LC), cosmesis and toxicity in patients (pts) with non-melanoma skin cancer (NMSC) treated with high-dose-rate brachytherapy (HDR-BT) treatment, plesiotherapy modality with radical or adjuvant intention in our hospital. Materials and Methods Retrospective study of 280 pts with 343 NMSC lesions, Tis (4.4%), T1 (77.6%) and T2 (18.1%) stage treated from May 2015 to September 2018. The median age was 76,8 (29-97) 50,1% >80 years-old; 62.1% males. ECOG 0 (52,5%). NMSC lesions were treated with Valencia applicators (35%), flaps (15,7%), silicone custom-made moulds (47,5%) and thermoplastic masks (1,7%). Hipofracionated treatment (42 Gy;6 Gy/fraction;2 week-days) with an equivalent 2 Gy dose (a/b 10) of 56 Gy was the most used scheme. All the lesions were limited 3-4 mm depth. Basal-cell carcinoma (87,2%) and face (69,1%) were the most frequent histological type and location respectively. Kaplan-Meier curves have been used for the statistical analysis of survival. Treatment-related toxicity was assessed using RTOG and the NCI-Common Terminology Criteria for Adverse Events guidelines.