ESTRO 36 Abstract Book

S224 ESTRO 36 2017 _______________________________________________________________________________________________

Nice, France 5 Peter MacCallum Cancer Centre, Division of Radiation Oncology, Melbourne, Australia 6 Goethe University Frankfurt, Department of Radiotherapy and Oncology, Frankfurt am Main, Germany Purpose or Objective Optimal timing of surgery after neoadjuvant chemo- radiotherapy (NAD-CRT) is still controversial. Literature data suggest an improvement in pathological complete response (pCR) after prolongation of surgical interval (SI) after NAD-CRT. The aim of this study was to evaluate the effects of SI on pCR in a pooled dataset of locally advancer rectal cancer (LARC) patients (pts) coming from 7 randomized trials. Material and Methods Pts data were extracted from the following LARC trials: Accord 12/0405, EORTC 22921, FFCD 9203, CAO/ARO/AIO- 94, CAO-ARO-AIO-04, INTERACT and TROG 01.04. Inclusion criteria for pts selection were: LARC (clinical tumor stage (cT) 3-4, clinical nodal stage (cN) 0-1-2 and no distant metastases) and NAD-CRT followed by surgery. The SI was calculated from the end of NAD-CRT. Pts were divided into two groups according to median of the surgery time (MST): shorter interval group (SIG) (pts who had surgery before MST) and longer interval group (LIG) (pts who had surgery after MST). The primary outcome was to determine the rate of pCR related to SI. The secondary outcome was to compare post-surgical complications in two groups and the impact of pCR rates on local recurrence (LR), metastases- free survival (MFS) and overall survival (OS). Pearson's Chi- squared test, Kaplan-Meier curves and univariate logistic regression model (uLRM) were used for data analysis. A p- value<=0.05 was considered significant. Results This pooled dataset included 5247 pts; 3078 pts satisfied the inclusion criteria and were analyzed in this study. Recruitment in the period investigated by the study took place as follows: 453 pts from 1993 to 1998, 613 from 1999 to 2003, 1023 from 2004 to 2008 and 996 from 2009 to 2014. 440 (14%) pts had pCR. The cumulative pCR rate rose significantly when time between NAD-CRT and surgery was increased, until reaching a plateau at 16 weeks (Figure 1). MST was 6 weeks (range 1-31, range interquartile 5-7). The SIG and the LIG had 1953 and 1132 pts, respectively. pCR rates were significantly higher in the LIG as compared to the SIG (19% vs 11.6%, p<0.01). cT, cN, surgery procedure and post surgical complications were distributed equally between the two groups. The results of uLRM are summarized in table 1. Finally, considering only the pCR events there was no statistically significant difference in term of LR, MFS and OS between the two groups. Comparing the two groups, considering pCR and no pCR pts, there was no statistically significant difference in term of LR, MFS and OS between them.

were validated using external validation of type 2b. The models performance was evaluated using the Area under the Receiver Operating Curve (AUC) and the brier score. Results Three thousand seven hundred seventy patients out of 7612 patients in this pooled dataset satisfied the inclusion criteria and were analyzed in this study. For each outcome (LR, DM and OS) performance of training and validation models, in terms of AUC and brier score were shown in table 1. Nomograms were generated for each outcome (LR, DM and OS) at 2, 3, 5 and 10 years. Furthermore as an example we have reported the new distant metastases nomogram at 5 years obtained (Figure 1).

Conclusion The logistic regression models performed with AUC values always higher than 0.7. The AUC higher in validation than in training would need further investigation. Nomograms will be totally showed at the conference. [1] V. Valentini et al;Journal Clinical Oncology; 2011 [2] S. Gary et al; Research reporting method; 2015 OC-0428 Surgical time to increase pCR in rectal cancer: pooled set of 3078 patients from 7 randomized trials G. Chiloiro 1 , C. Masciocchi 1 , J. Van Soest 2 , E. Meldolesi 1 , M. Gambacorta 1 , J. Bosset 3 , J. Doyen 4 , J. Gerard 4 , S. Ngan 5 , C. Roedel 6 , F. Cellini 1 , A. Damiani 1 , N. Dinapoli 1 , P. Lambin 2 , A. Dekker 2 , V. Valentini 1 1 Università Cattolica del Sacro Cuore -Policlinico A. Gemelli, Radiation Oncology Department, Rome, Italy 2 Maastricht University Medical Center, Department of Radiation Oncology MAASTRO-GROW School for Oncology and Development Biology, Maastricht, The Netherlands 3 Besançon University Hospital J Minjoz, Department of Radiation Oncology, Besançon, France 4 Unicancer Centre Antoine Lacassagne, Radiotherapy,