P2.05-018 Re-Irradiation Using SBRT: A Good Option As a Salvage Treatment in Pulmonary Lesions

Isolated intrathoracic relapse is common across distinct tumors and especially in lung cancer. Patients who received previous radiotherapy treatment (PRT) are not suitable for salvage surgery and chemotherapy provides poor local control. This study aimed to assess the toxicity and outcome of SBRT re-irradiation (reRT) in patients with solid tumors who developed an intrathoracic relapse. 35p treated with PRT who received salvage SBRT were identified in our database and their medical records were retrospectively reviewed. All patients underwent complete pulmonary function tests (cPFTs) (including DLCO, FEV1 and FVC) and PET-CT scan was performed before and after receiving lung reRT. Treatment planning was based on image fusion with the previous treatment plan and calculating the cumulative total nominal dose. Survival estimations were performed using Kaplan-Meier and differences between PFTs prior and post-reRT were analyzed using Student T-Test. Early toxicity was defined when it occurred up to 6 months. Median age: 68 (r53-81); 29p (83%) were male The previous treatments SBRT in 17p (49%), 3D-RT 4p (11%) and CT+RT 14p (40%) Mean RT dose 60,4Gy (r34-74). Primary tumors: lung 24 (69%), colorectal 9 (25%), oesophagus 2 (6%). For lung cancer p, the stage distribution was: IA 8 (23%), IB 2 (6%), IIA 2 (5.7%), IIB 1 (3%), IIIA 5 (4%), IIIb 4 (11%), IV 2 (6%). For other primaries, 8p (23%) were non metastatic at diagnosis and developed oligoprogressive disease in thorax which was treated with SBRT and 3 (8.5%) were oligometastatic. The location of reRT site: same lobe 17 (48%), ipsilateral different lobe 7 (20%), contralateral lobes 11 (32%). Median delivered dose of salvage SBRT was 50Gy (50-60) in 10 fractions (r3-10). Median accumulated dose in the lung was 81Gy (r60.10Gy-176Gy). With a median follow-up of 10m local control rate was 74% (IC 95%; 0.59-0.9) and 1-year OS was 84% (IC 95%;0.67-1). The metabolic complete response rate was 23%. No differences in the baseline and post re-irradiation PFTs were observed: FEV1, FVC and DLCO difference and CI95% were 2.41 (-1.79-6.62); 65 (-125-257) and 12.5 (-95 - 121). Asthenia GII in 12p (31%) was the most frequent acute toxicity, no long-term toxicities were detected. Salvage SBRT for treating isolated intrathoracic relapses achieved an outstanding local control and overall survival in selected p . This treatment did not impair post-reirradiation PFT and long-term toxicities were not observed.