ESTRO 37 Abstract book

S742

ESTRO 37

Results 12 weeks after therapy there was a statistically significant correlation between difference in DLCO and the maximum ΔHU (correlation coefficient (r) = -0,374, p = 0,007) as well as the difference in TLC and the minimum ΔHU (r = -0,348, p = 0,012). 6 months after treatment there was a significant correlation between the difference in VC lung and several density parameters, e.g. the mean (r = -0,358, p = 0,022) and median lung density changes (r = -0,349, p = 0,024) and the 75 th percentile of ΔHU (r = -0,366, p = 0,018). Also for the DLCO numerous correlations could be detected, e.g. the mean (r = -0,456, p = 0,004) and median lung density changes (r = -0,427, p = 0,008) as well as the 25 th (r = - 0,370, p = 0,022), 75 th (r = -0,433, p = 0,007) and 95 th percentile of ΔHU (r = -0,478, p = 0,002). There was no significant correlation between the PFT parameters FEV1, pCO 2 and pO 2 and any lung density parameter at any follow up appointment. Conclusion There is a significant correlation between DLCO, VC and ΔHU 6 months after treatment that most likely reflects the underlying pathological mechanisms in terms of the development of fibrotic lung tissue after RT. The relevance of the significant correlations 12 weeks after RT is questionable due to the early timing for fibrotic changes and possible overlap with (subclinical) radiation pneumonitis at this time of the follow-up. EP-1359 Preoperative high doses chemoradiotherapy in stage IIIA-N2 NSCLC on behalf of GOECP/SEOR-GICOR F. Counago 1 , N. Rodriguez de Dios 2 , S. Montemuño 3 , M. Martin 4 , P. Calvo-Crespo 5 , M.P. Samper-Ots 6 , P. Alcantara 7 , J. Corona 7 , J.L. Lopez-Guerra 8 , M. Murcia- Mejía 9 , M. López-Mata 10 , J. Jové-Teixidó 11 , M. Chust 12 , V. Díaz-Díaz 13 , L. De Ingunza-Barón 13 , T. García-Cañibano 3 , M.L. Couselo 14 , E. Del Cerro 15 , J. Moradiellos 16 , S. Amor 16 , A. Varela 16 , D. Sanz-Rosa 17 , I.J. Thuissard 17 , P. M. M. 18 , B. Taboada 19 1 Hospital Universitario Quirónsalud Madrid, Radiation Oncology, Madrid, Spain 2 Hospital del Mar, Radiation Oncology, Barcelona, Spain 3 Hospital Universitario de Fuenlabrada, Radiation Oncology, Madrid, Spain 4 Hospital Universitario Ramon y Cajal, Radiation Oncology, Madrid, Spain 5 Complexo Hospitalario Universitario Santiago de Compostela-, Radiation Oncology, A Coruña, Spain 6 Hospital Universitario Rey Juan Carlos, Radiation Oncology, Madrid, Spain 7 Hospital Universitario Clínico San Carlos, Radiation Oncology, Madrid, Spain 8 Hospital Universitario Virgen del Rocio, Radiation Oncology, Sevilla, Spain 9 Hospital Universitari Sant Joan de Reus, Radiation Oncology, Tarragona, Spain 10 Hospital Clinico Universitario Lozano Blesa, Radiation Oncology, Zaragoza, Spain 11 Hospital Germans Trias i Pujol, Radiation Oncology, Badalona, Spain 12 Instituto Valenciano de Oncologia, Radiation Oncology, Valencia, Spain 13 Hospital Universitario Puerta del Mar, Radiation Oncology, Cádiz, Spain 14 Hospital Central de la Defensa Gómez Ulla, Radiation Oncology, Madrid, Spain 15 Hospital Universitario Quirónsalud Madrid., Radiation Oncology, Madrid, Spain 16 Hospital Universitario Quirónsalud Madrid, Thoracic Surgery, Madrid, Spain 17 Universidad Europea de Madrid, School of Doctoral Studies & Research, Madrid, Spain 18 Hospital Universitario Miguel Servet, Radiation Oncology, Zaragoza, Spain

this analysis we focused on the changes in Hounsfield units (ΔHU) and the correlation with the corresponding

radiation dose after RT. Material and Methods

Follow-up CT data of patients that received radio- (chemo-)therapy for thoracic carcinomas was available for 61 patients 12 weeks after therapy and 51 patients 6 months after therapy. Pre- and post-RT CT scans were matched and ΔHU was calculated using customized research software. ΔHU was calculated in 5-Gy-intervals and the correlation between ΔHU and the corresponding dose was calculated as well as the regression coefficients. Additionally the mean ΔHU and ΔHU in 5-Gy- intervals were calculated for each tumor entity. Results The mean density changes at 12 weeks and 6 months post RT were 28,16 HU and 32,83 HU. The correlation coefficient between radiation dose and ΔHU for all available values was 0,162 (p=0,000). When looking at 12 weeks and 6 months individually the coefficients were 0,166 (p=0,000) and 0,158 (p=0,000). The resulting regression coefficient was 1,516 HU/Gy (p=0,000) for all values and 1,439 HU/Gy (p=0,000) and 1,612 HU/Gy (p=0,000) at 12 weeks and 6 months. The individual regression coefficients for each patient range from -2,23 HU/Gy to 7,46 HU/Gy at 12 weeks and -0,45 HU/Gy to 10,51 HU/Gy at 6 months. When looking at the three tumor entities individually the highest ΔHU at 12 weeks was seen in patients with SCLC (38,13 HU) and at 6 month in those with esophageal carcinomas (40,98 HU). Conclusion For most dose intervals there was an increase of ΔHU with an increased radiation dose. This is reflected by a statistically significant, although low correlation coefficient. The regression coefficients of all patients show large interindividual differences. EP-1358 Correlation between changes in lung function and lung density after radiotherapy for thoracic cancer C. Schröder 1 , R. Engehart-Cabillic 2 , H. Vorwerk 2 , M. Schmidt 3 , W. Huhnt 3 , E. Blank 3 , D. Sidow 3 , S. Kirschner 3 , A. Buchali 3 1 University Hospital Zürich, Clinic for Radiation Oncology, Zürich, Switzerland 2 University Clinic Giessen and Marburg, Clinic for Radiotherapy and Radiation Oncology, Marburg, Germany 3 Ruppiner Kliniken GmbH, Department of Radiation Oncology, Neuruppin, Germany Purpose or Objective In this analysis we focused on the correlation of a patients’ lung function (PFT) data and lung density changes (ΔHU) detected in follow up CTs in patients after high dose radio-chemotherapy of intrathoracic carcinomas. Material and Methods PFT and lung function data was available for 58 patients 12 weeks and 47 patients 6 months after radio-(chemo- )therapy for thoracic carcinomas (NSCLC, SCLC and esophageal carcinoma). NSCLC patients were treated with a total radiation dose of 74 Gy, SCLC patients with 60 Gy and patients with esophageal carcinoma with 66 Gy. Fraction dose was 2 Gy each. Eligible patients received chemotherapy according to intradepartmental standards. All patients completed the treatment protocol. Patients received follow up CT scans 12 weeks and 6 months after RT which were matched with the planning CT scans of each patient and then subtracted to calculate ΔHU for each voxel using customized research software. PFT data regarding e.g. vital capacity (VC), total lung capacity (TLC) and diffusion capacity for carbon monoxide (DLCO) were collected before and at several follow up appointments after treatment.