ESTRO 2024 - Abstract Book

S1761

Clinical - Lung

ESTRO 2024

Aiko Koba , Kazuhiko Hayashi, Osamu Suzuki, Yoshifumi Kawaguchi, Kazuhiko Ogawa and Masachi Chatani. Stereotactic body radiotherapy feasibility for patients with peripheral stage Ι lung cancer and poor pulmonary function. Oncology Letters 19: 2515-2521, 2020

2638

Proffered Paper

Toxicity analysis of high dose re-irradiation of in-field recurrent lung cancer: a prospective trial

Marloes Duijm 1 , Eugenio Cammareri 1 , Patrick V. Granton 1 , Wilco Schillemans 1 , Steven Petit 1 , Jose Belderbos 2 , Erik van Werkhoven 1 , Robin Cornelissen 3 , Joost Knegjens 2 , Joost Nuyttens 1 1 Erasmus MC Cancer Institute, University Medical Center Rotterdam, Department of Radiotherapy, Rotterdam, Netherlands. 2 The Netherlands Cancer Institute, Department of Radiation Oncology, Amsterdam, Netherlands. 3 Erasmus MC Cancer Institute, University Medical Center Rotterdam, Department of Pulmonary Medicine, Rotterdam, Netherlands

Purpose/Objective:

In the past re-irradiation of recurrent lung cancer within a previously irradiated area in the thorax has caused severe toxicity as fatal pneumonitis, tracheal fistula and massive bleeding. Since the introduction of new and more conventional radiotherapy techniques, organs at risk (OAR) can be avoided which has given new opportunities within the field of reirradiation of (marginal) in-field recurrences. However, clear accumulated dose constraints of the OAR are missing, making it hard to treat these recurrences with curative dose. We started a prospective multicenter phase II reirradiation study using cumulative constraints of 110Gy EQD 2,3 , 100Gy EQD 2,3 and 75Gy EQD 2,3 D max to the tracheobronchial tree, esophagus and spine, respectively. Our goal was to re-irradiate patients with a curative dose while respecting the dose to the OAR and in this way prolonging survival to 12 months while avoiding severe toxicity. Hereby we report the toxicity and dosimetric results of this RETHO study (NL59876.078.17). Patients previously treated with radiotherapy to the thorax having recurrent lung cancer were included if irradiation in radical setting (dose of ≥45Gy in an equivalent dose of 2Gy (EQD 2 )) was considered possible. The recurrence had to be located within 5 cm of the high dose region (50Gy EQD 2,10 ) of the previous irradiation and the interval between initial treatment and reirradiation had to be ≥9 months. Patients were treated with conventional (chemo)radiotherapy or stereotactic radiotherapy. In order to accumulate the treatment plans, doses in the treatment plans were re-calculated to an EQD 2 . For each organ individually (spine, heart, esophagus and bronchial tree) rigid image registration was applied. The doses of the initial treatment plan and the reirradiation plan were accumulated and corresponding dose volume histograms were extracted. PTV underdosage was allowed to respect the accumulated OAR dose constraints. Material/Methods: