ESTRO 36 Abstract Book

S169 ESTRO 36 2017 _______________________________________________________________________________________________

biological agents and tailor treatment-adaptive strategies based on initial response in early phase trials in the era of personalized medicine. Further examination and validation of TRG as surrogate for DFS based on large independent phase III trials is needed and should be enhanced for its implementation in the regular pathologic work-up. PV-0326 Time to surgery and pCR after neoadjuvant CRT in rectal cancer: a population study on 2113 patients G. Macchia 1 , M. Gambacorta 2 , G. Chiloiro 2 , G. Mantello 3 , A. De Paoli 4 , G. Montesi 5 , A. Sainato 6 , M. Lupattelli 7 , L. Caravatta 8 , F. Perrotti 9 , M. Rosetto 10 , F. Filippone 11 , R. Niespolo 12 , M. Osti 13 , L. Belgioia 14 , C. Boso 15 , A. Fontana 16 , S. Parisi 17 , A. Galardi 18 , L. Turri 19 , P. Sciacero 20 , L. Giaccherini 21 , C. Masciocchi 2 , A. Morganti 21 , V. Valentini 2 1 Fondazione di Ricerca e Cura “Giovanni Paolo II, Radiotherapy Unit, Campobasso, Italy 2 Fondazione “Policlinico Gemelli”- Università Cattolica S. Cuore, Department of Radiotherapy, Roma, Italy 3 Azienda Ospedaliero Universitaria- Ospedali Riuniti, Radiotherapy Unit, Ancona, Italy 4 Oncological Referral Center, Radiation Oncology Department, Aviano, Italy 5 ULSS18, Radiotherapy Unit, Rovigo, Italy 6 University Hospital, Radiotherapy Unit, Pisa, Italy 7 'S. Maria della Misericordia' Hospital, Radiotherapy Unit, Perugia, Italy 8 'A. Businco' Regional Oncological Hospital, Radiation Oncology Department, Cagliari, Italy 9 'SS Annunziata' Hospital- 'G. D'Annunzio' University, Radiotherapy Unit, Chieti, Italy 10 Ospedale Belcolle, Radiotherapy Unit, Viterbo, Italy 11 Azienda ospedaliera Papa Giovanni XXIII, Radiotherapy Unit, Bergamo, Italy 12 Azienda Ospedaliera S. Gerardo-, Radiotherapy Unit, Monza, Italy 13 Facoltà di Medicina e Psicologia- Università Sapienza, Department of Radiation Oncology, Roma, Iceland 14 AOU IRCCS San Martino- IST National Cancer Research Institute, Radiotherapy Unit, Genova, Italy 15 Veneto Institute of Oncology-IRCCS, Radiotherapy and Nuclear Medicine Unit, Padova, Italy 16 Ospedale S.M. Goretti, Radiotherapy Unit, Latina, Italy 17 Casa Sollievo della Sofferenza- IRCCS-CSS, Radiotherapy Unit, San Giovanni Rotondo, Italy 18 Florence University, Department of Radiotherapy, Firenze, Italy 19 'Maggiore della Carità' Hospital, Radiotherapy Unit, Novara, Italy 20 ASL TO4- General Hospital, Radiotherapy Unit, Ivrea, Italy 21 Policlinico Universitario S. Orsola Malpighi, Radiotherapy, Bologna, Italy Purpose or Objective Population based electronic health records, provide a means of obtaining information on patient characteristics and outcomes that can then be compared with the more selected populations recruited within randomized controlled trials. Aim of this analysis was to retrospectively evaluate the difference in terms of pathologic complete response (pCR) according to time elapsed between chemoradiation (CRT) and surgery on a large unselected real-life dataset of locally advanced rectal cancer (LARC) patients. Material and Methods A multicentre retrospective cohort study of LARC patients among 21 Italian Radiotherapy Institutions was performed. 3D conformal or intensity-modulated radiation treatment was required as inclusion criteria. Surgery was performed according to the principles of total mesorectal excision (TME). Patients were stratified according to 3 different

Conclusion 18 FDG-PET is able to define active bone marrow within pelvic osseous structures. ACT BM is a predictor of decreased blood cells nadirs in anal cancer patients undergoing concurrent chemo-radiation. Lumbar-sacral bone marrow dose seems to be the strongest predictor. PV-0325 Tumor Regression Grading in the CAO/ARO/AIO-04 phase 3 trial in locally advanced rectal carcinoma E. Fokas 1 , M. Ghadimi 2 , R. Fietkau 3 , P. Ströbel 4 , A. Hartmann 5 , R. Sauer 6 , T. Liersch 2 , T. Hothorn 7 , C. Wittekind 8 , C. Rödel 1 1 Goethe University Frankfurt, Department of Radiotherapy and Oncology, Frankfurt, Germany 2 University of Göttingen, Department of General- Visceral and Pediatric Surgery, Göttingen, Germany 3 University of Erlangen, Department of Radiation Oncology, Erlangen, Germany 4 University of Göttingen, Deparment of Pathology, Göttingen, Germany 5 University of Erlangen, Deparment of Pathology, Erlangen, Germany 6 University of Erlangen, Deparment of Radiation Oncology, Erlangen, Germany 7 University of Zurich, Epidemiology- Biostatistics and Prevention Institute, Zurich, Switzerland 8 University of Leipzig, Institute of Pathology, Leipzig, Germany Purpose or Objective We examined the prognostic value of tumor regression grading (TRG) in 1208 patients with locally advanced rectal carcinoma treated within the CAO/ARO/AIO-04 trial after a median follow-up of 50 months. Material and Methods TRG and clinicopathologic parameters were correlated to clinical outcome. Statistical differences between groups were calculated by the Log-rank test, and incidence curves were plotted using the Kaplan-Meier method. The Cox regression and the Fine-Gray models were used for the multivariate analysis. We used the four Prentice criteria (PC1-4) to assess the surrogacy of TRG for disease-free survival (DFS). Results The 3-year cumulative incidence of DFS, distant metastases, local recurrence and overall survival (OS) were 64.6%, 25.4%, 6.9% and 76.8% for patients with TRG 0+1 (poor regression), 77.6%, 18.3%, 3.3% and 89.2% for TRG 2 + 3 (intermediate regression), and 92.3%, 4.1%, 0% and 96.2% for TRG 4 (complete regression), respectively (P < .001, for all four endpoints). Due to multicollinearity, TRG 4 and pathologic stage was not assessed within the same model. TRG 2+3 vs TRG 0+1 after preoperative CRT remained an independent prognostic factor for DFS (HR, 0.677; P = .007), the cumulative incidence of local recurrence (HR, 0.504; P = .028) and OS (HR, 0.582; P < .001). Notably, TRG satisfied PC1-3 for individual-level surrogacy (P = .037, P < .001 and P < .001, respectively). The treatment effect on DFS was captured by TRG and therefore PC4 satisfaction is plausible. Conclusion TRG following preoperative chemoradiotherapy predicted for a favorable long-term outcome in multivariate analysis. In the era of personalized medicine. TRG might constitute an attractive option to validate molecular biomarkers, facilitate successful clinical testing of new