ESTRO 2023 - Abstract Book

S1048

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ESTRO 2023

underwent Volumetric Modulated Arc Therapy (VMAT) technique, and the schedule of treatment most represented was 48 Gy in 8 fractions (range 23-60 Gy in 1-8 fractions). The medium BED10 was 86 Gy (range 48-120 Gy). The medium volume of CTV treated was 10 cc (range 0.74-60.3 cc). Toxicity assessment has been considered in acute and in late (more than 3 months after SBRT) for pulmonary district, according to Common Terminology Criteria for Adverse Events (CTCAE v4.0) scoring system. Survival outcomes were calculated through Kaplan-Meier curves. Results Median survival was 23 months. The acute and late toxicities was < Grade 2 for all parameters for all pts. At 1- and 3-years survival probability were as follows: local control (LC) 89% and 83%, loco regional nodal control (LRNC) 81% and 70%, distant nodal control (DNC) 92% and 88%, distant metastasis free survival (DMFS) 49% and 36%, overall survival (OS) 66% and 35% respectively. At univariate analysis, the volume of CTV (> 10 cc) was associated with worst results in terms of DMFS and OS with statistically significant data (P = 0,0281 and P = 0,0015 respectively). Conclusion The application of SBRT for mediastinal and hilar LN, especially in the oligometastatic patient with lung cancer, improve local control (LC) and other outcomes with limited toxicity, with evidence that CTV volume is an unfavorable factor in terms of DMFS and OS. A. Nuccio 1,3 , M. Torrisi 2,4 , F.R. Ogliari 1 , L. Giannini 2,4 , M. Pasetti 2 , A. Fodor 2 , C.R. Gigliotti 5 , C. Fiorino 5 , S. Arcangeli 4,6 , A. Bulotta 1 , I. Dell'Oca 2 , S. Cascinu 7,8 , N.G. Di Muzio 9,10 1 IRCCS San Raffaele Scientific Institute, Department of Oncology, Milan, Italy; 2 IRCCS San Raffaele Scientific Institute, Department of Radiation Oncology, Milan, Italy; 3 Vita-Salute San Raffaele University, Department of Oncology, Milan, Italy; 4 University of Milano-Bicocca, Department of Radiation Oncology, Milan, Italy; 5 IRCCS San Raffaele Scientific Institute, Department of Physics, Milan, Italy; 6 ASST Monza, Department of Radiation Oncology, Monza, Italy; 7 IRCCS San Raffaele Scientific Institute, Department of Oncology, Milan, Italy; 8 Vita-Salute San Raffaele University, Department of Oncology, Milan, Italy; 9 Vita-Salute San Raffaele University, Department of Radiation Oncology, Milan, Italy; 10 IRCCS San Raffaele Scientific Institute, Department of Radiation Oncology, Milan, Italy Purpose or Objective In Epidermal Grow Factor Receptor (EGFR) mutant non-small-cell lung cancer (NSCLC), local radiotherapy (RT) has become a new standard of care, improving OS in oligoprogressive disease during tyrosine kinase inhibitors (TKIs) treatment. Indeed, TKIs have radiosensitizing effects, but combined with consolidation thoracic RT might cause an impairment of normal lung function, due to possible toxicity arising from their combination. This leads, in clinical practice, to stop TKIs when RT is ongoing. As few data are available in this therapeutic setting, we evaluated the feasibility and tolerance of Intensity Modulated RT (IMRT) delivered by means of Helical Tomotherapy (HT) or Stereotactic Body Radiotherapy (SBRT) delivered by Cyberknife (CK) in pts with EGFR mutant NSCLC under TKIs treatment. Materials and Methods Between April 2017 and January 2022, 18 patients (pts) with stage IV NSCLC treated with concomitant RT (60-62.5 Gy/25 30 fractions IMRT and 40-60 Gy/3-8 fractions SBRT) and TKIs were evaluated retrospectively. Our main endpoint was lung toxicity, while OS was secondarily described. Post-treatment scans, TC and PET, were used to evaluate local response at 3 and 6 months. Clinical and radiological acute toxicity was assessed according to the CTCAE v5.0. Survival curves were calculated from the date of treatment by using the Kaplan-Meier method. Results Median age of the pts at the time of RT was 69.4 years (45.4-83.6). Median follow up (FU) was 16.8 months (0.5-51.9). Median time occurring between start of TKIs and beginning of RT was 9.39 months (1.1-71). Treatments were delivered with HT (14/18) and CK (4/18). The mean PTV was 114.92cc (8.69-379.5 cc). Mean lung 2 Gy Equivalent Dose was 12.4 Gy (7.2-21.1 Gy). TKIs administrated were Osimertinib (9/18), Erlotinib (4/18), Gefitinib (3/18) and Afatinib (2/18). Median OS was 37.1 months. Median progression free survival (PFS) from the beginning of EGFR-TKI treatment was 21,5 months (6 78 months). Median PFS after concomitant EGFR-TKI/RT was 7.7 months (0.5-56 months). Acute toxicity was observed in 70% of pts, of them 75% (9/12) G1 and 25% (3/12) G2; 25% (3/12) needed corticosteroids and antibiotic therapy. Patients showed local complete response (23%), partial response (47%), stable disease (18%) and progression of disease (12%). At 6 months FU 41% pts showed G1 radiological toxicities, none of those needed medical therapy, while 59% G0. Patients showed local complete response (41.5%), partial response (23.5%) and disease progression (35%). Conclusion Our findings show that the association between thoracic RT and the administration of TKIs is safe and well tolerated. Although differences in treated volume and dose/fraction occurred between IMRT and SBRT, no increased toxicity has been recorded, thus suggesting the feasibility of the association of these different treatment modality. The analysis of a larger sample and a longer clinical follow-up are needed to confirm these preliminary results. PO-1308 Thoracic Radiotherapy and Tyrosine Kinase Inhibitors Association: Single-center Preliminary Results

PO-1309 Survival differences of hypofractionation vs. standard-fractionation in lung cancer: a cohort study

M.M. Teja Ubach 1 , Á. Manso de Lema 1 , R. Matute Martín 2 , E. González del Portillo 1 , M. González Cantero 1 , M.I. Garrido Botella 1 , M. Rodríguez Roldán 1 , R. Rosel Aller 1 , I. Rodríguez Rodríguez 1 , R. Morera López 1 1 Hospital Universitario La Paz, Radiation Oncology, Madrid, Spain; 2 Centro de Protonterapia Quirónsalud, Radiation Oncology, Madrid, Spain