ESTRO 36 Abstract Book

S171 ESTRO 36 _______________________________________________________________________________________________

time intervals. The 1 st group included 305 patients undergone TME within 6 weeks, the 2 nd group included 1610 patients undergone TME within 7-12 weeks, and the 3 rd group included 198 patients undergone TME within 13 or more weeks after CRT, respectively. Results Data on 2113 patients treated between 1997 and 2016 were retrieved from the historical database of gastrointestinal radiation oncologists joined into the study. Recruitment in the period investigated by the study took place as follows: 183 patients from 1997 to 2002, 550 from 2003 to 2008, and the majority, 1380, from 2009 to 2016. Five hundred and eighty two patients had stage II (T3–4, N0) and 1531 had stage III (any T, N1–2) histological proven invasive rectal adenocarcinoma. A CRT schedule with one (1600 pts) or 2-drugs was administered (513 pts). Overall, pCR were 468 (22%). Among the 2113 assessable patients the proportion of patients achieving a pCR increased according with time interval, as follows: 12.4% (1 st group), 22.9% (2 nd group), and 30.8% (3 rd group) (p<0.001, ANOVA test), respectively. The 1 st group had a pCR odds ratio of 0.47 compared to 2 nd group, while the latter had a pCR odds ratio of 0.66 compared to 3 rd group. Moreover, 1 st group had a pCR odds ratio of 0.31 compared to 3 rd group. The rate of complete response increments for each week of waiting was 1.5% (about 0.2%/die) . At univariate analysis, time interval (p<0.001), radiotherapy dose (>5040 cGy; p=0.013), and clinical tumor stage (p=0.029) were significantly correlated to pCR. The positive impact of time interval (p<0.001) and clinical tumor stage (p=0.038) were confirmed by multivariate analysis, in agreement with the literature data (Table 1).

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 We confirmed on a population-level that lengthening the interval (>13 weeks) from CRT to surgery improves the pCR in comparison to historic data, possibly due to technical improvement of radiotherapy such as the ability of high- precision dose delivery and real-time knowledge of the target volume location. PV-0327 The effect of postoperative complications on Quality of Life in elderly rectal cancer patients A.M. Couwenberg 1 , F.S.A. De Beer 1 , M.P.W. Intven 1 , M.E. Hamaker 2 , W.M.U. Van Grevenstein 3 , H.M. Verkooijen 4 1 UMC Utrecht, Radiotherapy, Utrecht, The Netherlands 2 Diakonessenhuis, Geriatrics, Utrecht, The Netherlands 3 UMC Utrecht, Surgery, Utrecht, The Netherlands 4 UMC Utrecht, Imaging Division, Utrecht, The Netherlands