ESTRO 2025 - Abstract Book

S1582

Clinical – Mixed sites & palliation

ESTRO 2025

4213

Digital Poster Four years' experience of thoracic re-irradiation in a single centre. sunyach marie 1 , Sandt Magali 2 , Dupuis Pauline 3 , Martel Isabelle 1 , Ayadi Myriam 1 1 Radiotherapy, Centre Leon Berard, lyon, France. 2 Radiotherapie, Centre Leon Berard, lyon, France. 3 Radiotherapie, Centre Leon Berard, Lyon, France Purpose/Objective: In our institution, we implemented a twice a week peer-review meeting to secure reRT. In the absence of standardized EQD2 cumulative dose guidelines, we discussed reRT patient cases with cumulative dose to concerned OARs that exceed the usual constraints. This study aimed at for curative thoracic reRT. Material/Methods: Our peer-review meetings consisted of a re- RT experts’ team, i.e senior radio -oncologists (RO) and physicists. For each reRT patient case, EQD2 cumulative dose assessment was performed using the MIM software. The indication and the feasibility of irradiation were evaluated. Treatment plan was validated or based on EQD2 cumulative dose to OARs. This retrospective study focused on curative thoracic reRT for which the interval between two irradiations was >1y. Results: A total of 58 patients were discussed for curative thoracic reRT. Thirty-six patients were re-irradiated for a recurrent primary tumor, with a median survival of 21 months. 15 were living last news, including 8 alive witout recurrence after > 2 years. For 2 patients, esophagus received an EQD2 cumulative max dose > 90 Gy. Both died at 6 and 30 months without complications. Three patients received EQD2 cumulative max dose to trachea > 80 Gy. 2 died at 3 and 29 months, and 1 is alive at 44 months. None presented complications. An EQD2 cumulative max dose > 90 Gy was delivered to the plexus for 2 patients. They both died at 25 and 38 months without complication.Two patients received a EQD2 cumulative max dose > 70 Gy to the spinal cord without complications at 32 and 40 months.For 8 patients, EQD2 cumulative max dose were superior to 95 Gy to large bronchus. Two of them lived more than 2 years after reRT without complications, while the others died also without complications. Mean pulmonary dose, estimated > 30 Gy in 8 patients, 2 died before 1 year, including one from radiation pneumonitis, 5 others died between 12 and 38 months, and 3 patients are alive at 22, 30 and 50 months without radiation pneumonitis.Tweenty-two patients underwent thoracic reRT for second cancer or metastasis. The median survival rate was 30 months. High cumulative doses of 200 Gy were reported to the chest wall, with no necrosis-type complications. Conclusion: Few complications were found confirming our process to be safe. However, patients re-irradiated for lung tumours have a modest life expectancy, and we feel it is important to take maximum precautions for thoracic re-irradiation, since only a small number of patients can benefit from it. References: Rulach, R., Ball, D., Chua, K. L. M., Dahele, M., De Ruysscher, D., Franks, K., Gomez, D., Guckenberger, M., Hanna, G. G., Louie, A. V., Moghanaki, D., Palma, D. A., Peedell, C., Salem, A., Siva, S., Videtic, G. M. M., Chalmers, A. J., & Harrow, S. (2021). An International Expert Survey on the Indications and Practice of Radical Thoracic Reirradiation for Non Small Cell Lung Cancer. Advances in Radiation Oncology , 6 (2), 100653. Slevin, F., Aitken, K., Alongi, F., Murray, L. J. (2021). An international Delphi consensus for pelvic stereotactic ablative radiotherapy re-irradiation. Radiotherapy and Oncology: Journal of the European Society for Therapeutic Radiology and Oncology , 164 , 104-114. Keywords: Re irradiation, thorax, tolerance