S770
Clinical - Lung
ESTRO 2026
compare favorably with previous reports and a low incidence of grade ≥ 3 acute toxicity. Distant pulmonary metastases were the predominant failure pattern, highlighting the need for systematic chest-CT follow-up. Further studies should refine indications for carbon-ion and definitive RT in tracheobronchial ACC. References: 1. Honings, J., et al., Incidence and treatment of tracheal cancer: a nationwide study in the Netherlands. Ann Surg Oncol, 2007. 14(2): p. 968-76.2. Madariaga, M.L.L. and H.A. Gaissert, Overview of malignant tracheal tumors. Ann Cardiothorac Surg, 2018. 7(2): p. 244-254.3. Chen, J., et al., Definitive carbon ion radiotherapy for tracheobronchial adenoid cystic carcinoma: a preliminary report. BMC Cancer, 2021. 21(1): p. 734.4. Jensen, A.D., et al., Combined intensity-modulated radiotherapy plus raster-scanned carbon ion boost for advanced adenoid cystic carcinoma of the head and neck results in superior locoregional control and overall survival. Cancer, 2015. 121(17): p. 3001-9. Keywords: tracheobronchial ACC, carbon-RT, survival analysis Digital Poster 1420 Radiation induced in situ pulmonary artery thrombosis in non-small cell lung cancer: A 10-year experience at a tertiary referral center in Thailand Napat Aksornprom, Danita Jintanapakdee, Wariya Jintanapakdee Department of Radiology, King Chulalongkorn Memorial Hospital, Bangkok, Thailand Purpose/Objective: Radiation induced in situ Pulmonary artery thrombosis (In situ PAT) is a possible complication found in patients treated with RT to the thoracic area but currently the information pertaining to this condition is extremely scarce even the incidence is unknown.We aim to investigate the incidence of radiation induced in situ PAT as well as risk factors in patients with non- metastatic NSCLC who received definitive RT or CCRT. Material/Methods: In this retrospective study, patients with nonmetastatic NSCLC who had been treated with definitive RT are reviewed for the incidence of in situ PAT through our database and confirmed with chest radiologist. The risk factors and survival data were collected, and pulmonary artery (PA) of each patient was contoured according to RTOG 1106 atlas and DVH were generated and assessed.
Results: From 2013 to 2022, 180 patients who receive definitive RT for NSCLC treatment were identified with the median follow up time of 2.8 years. Among them, twenty patients were diagnosed with in situ PAT, of whom four were symptomatic. Median time to developed PAT was 18.7 months and the 2, 3, and 5- years cumulative incidence are 0.09, 6, and 18.3 %, respectively. On multivariate analysis, the risk factors associated with increased risk of in situ PAT were Age ≥ 65 (hazard ratio [HR], 4.07 [95% CI, 1.35 to 12.25]; P = .03), PA mean dose ≥ 57.5 Gy (HR, 3.19 [95% CI, 1.30 to 7.84]; P = 0.012), and PA max dose ≥ 80 Gy (HR, 2.91 [95% CI, 1.14 to 7.45]; P = 0.026). The 2-year OS was 66.9% for the entire group However, the 2-year OS was higher in the group with in situ PAT (95% [95% CI, 69.5 to 99.3]) compared to those without in situ PAT (63.4% [95% CI, 55.4 to 70.4]). The multivariate analysis also confirms that in situ PAT has no detrimental effect on OS (HR, 2.21 [95% CI, 1.14 to 4.28]; P = 0.007). PA mean dose ≥ 57.5Gy, receiving RT dose <65 Gy and lack of PET staging were associated with worse OS. Conclusion: The incidence of radiation-induced in situ PAT in NSCLC patients after definitive RT is considerable and associated with older age, high mean and max dose to PA. The developed in situ PAT has no detrimental effect on the survival with higher 2-year OS. However, the validity of this association still needs to be tested in further larger study References: 1. Ahuja J, et al. In Situ Pulmonary Artery Thrombosis:
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