Abstract Book

S742

ESTRO 37

19 Complexo Hospitalario Universitario Santiago de Compostela, Radiation Oncology, A Coruña, Spain

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

Purpose or Objective We conducted a multi-institutional retrospective study comparing preoperative high doses chemoradiotherapy (pCRT) and preoperative chemotherapy (pCHT) in operable stage IIIA-N2 non-small-cell lung cancer (NSCLC). Material and Methods 99 patients with stage T1-T3N2M0 NSCLC treated with either high doses (60-66 Gy, 1.8-2 Gy/fraction) pCRT or pCHT (three cycles, mostly platinum-doublet) followed by surgery were identified between January 2005 and December 2014 at 14 hospitals in Spain. The study was supported by the Radiation Oncology Clinical Research Group (GICOR) and the GOECP-SEOR (Oncologic Group for the Study of Lung Cancer-Spanish Society of Radiation Oncology. Patient and tumor characteristics (age; gender; clinical T stage; number and size of involved nodal stations; histology) were similar (p >0.05) in both groups. Overall survival (OS) and progression-free survival (PFS) were estimated using the Kaplan-Meier method and compared using the log-rank test. Cox regression analysis was also performed. Results

47 patients were treated with pCRT and 52 with pCHT. Median follow-up was 41 months in the pCRT arm and 41.5 months in the pCHT arm. Surgery consisted of either lobectomy (87.2% in pCRT vs. 82.7% in pCHT) or pneumonectomy (12.8% in pCRT vs. 17.3% in pCHT). Postoperative radiotherapy was given to 57.6% of patients receiving pCHT. Adjuvant CHT was given to 14.9% of patients undergoing pCRT vs. 30.8% of patients undergoing pCHT (p=0.062). Nodal downstaging (to N1 or N0; 89.4% vs. 57.7%) and pathologic complete response (pT0pN0; 46.8% vs. 7.7%) were significantly higher in pCRT vs. pCHT group. Patients in the pCRT group experience fewer locoregional recurrences vs the pCHT group (8.5% vs. 13.5%, p = 0.047) and similar distant recurrences (31.9% vs. 34.6%, p=0.776). 4-year PFS (55.5% vs. 42.6%, log-rank p=0.505) and 4-year OS (61.8% vs. 58.1%, log-rank p=0.516) were similar for pCRT vs. pCHT group. Median PFS was 45 months in the pCHT group and not yet reached in pCRT group. Median OS was similar in both groups (61 months in pCRT vs. 56 months in pCHT, log-rank p=0.803). No differences were found in the overall grade ≥3 toxicity between the groups. One patient died from treatment-related causes in the pCRT group compared to none in the pCHT. Univariate analysis showed that the only factor associated with worse OS was an advanced pT stage (p<0.001). A higher pT stage (p<0.001) and persistent N2 (p=0.002) were independent prognostic factors associated with poorer PFS on multivariate analysis. Conclusion pCRT yields better nodal downstaging and pathologic complete response than pCHT . Moreover, patients