ESTRO 2024 - Abstract Book

S1769

Clinical - Lung

ESTRO 2024

Material/Methods:

22 patients with MPM oligo-recurrence were evaluated between January 2011 and December 2022 at our institute. All these patients had an histological diagnosis of MPM and underwent chemotherapy (adjuvant or neoadjuvant) with a platinum-based doublet. Surgery was also performed (biopsy by thoracoscopy, pleural decortication or pleurectomy plus decortication). The demographic and clinical characteristics of the patients are summarized in the Table. 1. All these patients received a radical radiotherapy treatment on the entire hemithorax using Helical Tomotherapy technology. The planning target volume (PTV) was delineated to include the entire thickness of the rib cage, the pericardium, the mediastinal lymph nodes and the diaphragm (up to L2). The total dose prescribed was 50 Gy in 25 fractions + concomitant boost (60 Gy in 25 fractions) on macroscopic residual disease. These patients started regular clinical-radiological follow-up (quarterly for the first two years and then every six months) through the alternating use of chest-abdomen CT with contrast medium and PET-CT. Patients who developed disease oligorecurrence at the ipsilateral pleural level (number of lesions ≤ 3) underwent retreatment with SABR. A 4Dimension-CT simulation was performed and diagnostic images were also used to delineate the clinical tumor volume (CTV) which was given a margin of 5 mm for the PTV. The prescribed dose ranged from 30 Gy to 25 Gy divided into 5-3 fractions taking into account the dose previously delivered to the organs at risk. To evaluate the clinical impact of SABR treatment, the time to further systemic therapy (TFST) was calculated as the primary outcome: the time from the start of retreatment to the first day of second-line systemic therapy or death. Survival (OS) and Progression Free Survival (PFS) were evaluated as secondary outcomes. Toxicity of radiation treatment were collected according to the "Common Terminology Criteria for Adverse Events" (CTCAE Ed.4.0) at the end of the hemithoracic irradiation and after SABR. The qualitative variables were analyzed through percentages. For each endpoint, the median time to event was calculated, with the respective interquartile range. For overall survival and progression-free survival, the survival probabilities, with the related confidence intervals, were calculated using the Kaplan-Meier method

Results: