ESTRO 2023 - Abstract Book

S1057

Digital Posters

ESTRO 2023

Ultra-central (UC) lung tumors are defined as those abutting the proximal bronchial trees. Stereotactic body radiation therapy (SBRT) for UC tumors is difficult due to concerns about serious toxicities. Therefore, we report safety and efficacy of moderate-intensity SBRT for UC tumors in our institution. Materials and Methods Patients with UC tumors underwent SBRT at a dose of 45 to 60 Gy in 10 fractions, with Dmax in the target volume not exceeding 110% of the prescribed dose. The primary outcomes were tumor response and overall survival (OS). Results From January 2017 to May 2021, we treated twenty patients who had been treated with UC tumors. The median follow-up time was 15.8 months (range: 2.7–53.8). Ten of the 20 patients (50.0%) showed a complete response (CR), five (25.0%) had a partial response (PR), two (10.0%) had stable disease (SD) and three (15.0%) showed progressive disease (PD); the response and disease control rates were 75.0% and 90.0%, respectively. PD patients showed local progression at median 8.3 months (range: 6.8-19.1) after SBRT. Fourteen patients were alive with no evidence of disease or with controlled disease until the last follow-ups. One-year, 2-year OS rate was 79.1% and 63.9%, respectively. Five patients died due to a non-RT cause. One patient experienced massive hemoptysis 6 months after SBRT, which resulted in death. One patient experienced grade 2 esophageal pain and another had grade 1 cough. Otherwise, no grade 3 or higher toxicities were reported. Conclusion Moderate-intensity SBRT might aid in achieving good control of UC tumors. SBRT is well-tolerated treatment modality for UC tumors. Future studies are warranted due to a small number of patients and short period of follow-up. G. Pozo Rodriguez 1 , A. Milanes Gaillet 1 , S. Guardado Gonzalez 2 , S. Fernández Alonso 2 , I. Alonso Delgado 3 , D. Martin Garcia 3 , P. Adaimi Hernandez 3 , R. Diaz Fuentes 3 , P. Botella Faus 1 , A. Gaitan Simon 3 , M. Manzano Rodriguez 3 , S. Pedraza Fernandez 4 , N. Gascon Costoso 4 , E. Cabello Murillo 3 1 h.U. 12 De Octubre, Medical Physics, Madrid, Spain; 2 h.U. 12 De Octubre, Radiation Oncology, Madrid, Spain; 3 h.U.12 De Octubre, Medical Physics, Madrid, Spain; 4 h.U.12 De Octubre, Radiation Oncology, Madrid, Spain Purpose or Objective To quantify the fraction of patients that underwent SBRT of lung and have exhibited chest wall toxicity after treatment, and its association with influential parameters. Materials and Methods Cohort of 50 SBRT lung patients treated in our institution were selected filtering by target location and only considering those abutting or invading chest wall (CW). SBRT treatments were performed on a Varian Clinac 2300 iX linear accelerator. It includes an On Board Imager unit to perform KVCBCT and a Millenium 120 MLC (5mm thickness at isocenter) for treatments performance (Varian Medical Systems, Palo Alto CA). Treatment Planning System used for clinical dosimetry was Eclipse 15.6, and two algorithms available: Acuros 15.6 and AAA 15.6 (Analytical Anisotropic Algorithm) configured with a 2.5 mm calculation grid . PO 15.6 optimizer was used for VMAT treatments. 4DCT was acquired with Philips Brilliance CT, using a nominal slice thickness of 2mm. Respiratory cycle was binned into 10 phases and ITV was generated by means of merging 10 segmented GTV. In our institution, patient medical history is stored in natural language format. To identify those patient who suffer any kind of toxicity after SBRT, the search included these keywords: ‘rib cage pain’ OR ‘fracture’ OR ‘cleft bone’ OR ‘callus’. Results A logistic regression has been performed with Stata v.16 (StataCorp.) to evaluate the influence of age, sex, location, bone density (osteoporosis) and BED metrics in CW toxicity (table I), finding no significant association. In agreement with UK Consortium and AAPM TG101, BED calculation has considered dose to volume constrains as shown in table II and III. Up to 22% of cases presented any kind of chest wall toxicity: 12% concerning CW injury and at least 10% developed rib cage pain. Only 8% of patients (2 female and 2 male) registered osteoporosis in their reports, coherent with Spanish prevalence for female and male > 50 years old. Time of diagnose ranged from 6.4 to 31.2 months (fracture, callus or cleft bone) and from 1.7 to 19.5 months (emerging pain). PO-1320 Chest Wall toxicity after lung SBRT treatments and influential parameters. Prescription BED to PTV ranged from 72 to 115.5Gy, and dosimetric chest wall parameters were extracted from DVH curves.