ESTRO 36 Abstract Book

S225 ESTRO 36 2017 _______________________________________________________________________________________________

by TME surgery and optional postoperative chemotherapy and an experimental arm B: short course 5 x 5 Gy radiation followed by six cycles of full-dose CAPOX or nine cycles of FOLFOX and TME surgery. Results A total of 920 patients were included between June 2011 and June 2016. At randomisation, 302 were cT4 and 828 were cN+, of whom 621 were considered cN2 disease and 137 as extramesorectal pelvic lymphnodes. Based on MRI, extramural vascular invasion was diagnosed in 275 patients, whereas the mesorectal fascia was threatened in 564 patients. Preliminary data show that median time between randomization and surgery was 15,9 weeks for arm A and 25,3 weeks for arm B. In arm B, 100% of the patients who started, completed the radiotherapy and 72% of patients completed all scheduled cycles of neoadjuvant chemotherapy after 5x5 Gy. Another 9% of patients completed the last course(s) without oxaliplatin. In arm A, 96% received all scheduled radiotherapy fractions and 94% of the patients received 5 weeks of preoperative capecitabine combined with radiotherapy. Open surgery was performed in 59% of the patients and 35% underwent an APR. In total, 19% of patients had a ypT0N0. For 4% of all patients a wait & watch strategy was applied. Of the operated patients, 89% had a negative circumferential resection margin (> 1 mm). Conclusion Compliance for neoadjuvant treatment was good in both treatment arms. Given the locally advanced state of most tumors, the ypT0N0 rate can be considered satisfactory. Final data and details concerning differences in pre- treatment characteristics and treatments between the two arms will be presented. SP-0430 Radiomics in radiology, what are the parameters of interest for different imaging modalities? H. Ahlström 1 1 Uppsala University, Dept of Radiology, Uppsala, Sweden CT, MRI, PET, PET-CT and PET-MRI datasets contain huge amounts of spatially detailed morphological, functional and metabolic information. Today, when analysed, these detailed datasets are typically heavily reduced to a few measurements of a priori specified measurements of interest (e.g. volumes, areas, diameters, average/maximum tracer concentrations etc.) and/or visually – and therefore inevitably subjectively – assessed by a human operator. As a result, normality/non-normality can only be assessed on these measurements and not on the entire data collected, and statistical interaction with non-imaging parameters can also be assessed only on these a priori specified measurements. In order to utilise the full potential of these image datasets, new analysis tools included in the concept Radiomics, that allow objective or quantitative assessment of all imaging data (including e.g. previously discarded information about texture), are needed. Radiomics can be divided into distinct processes: (a) image acquisition and reconstruction, (b) image segmentation and rendering, (c) feature extraction and feature qualification and (d) databases and data sharing with non-imaging data (e.g. different “omics” and clinical data) for (e) informatics analyses. Statistical knowledge of the normal range of Radiomics features are needed for the analyses. These analyses are anticipated to bring out new associations and understandings that traditional approaches could not achieve. Radiomics features can, together with non- imaging data, be included in models that have shown to Joint Symposium: ESTRO-ESR: Radiomics and imaging databases for precision radiation oncology

Conclusion The results of these pooled analyses confirm that the prolongation of SI after the end of NAD-CRT increased the rate of pCR in LARC pts. The cumulative pCR rate reached a plateau at 16 weeks; moreover longer SI has no impact on post surgical complication rates. No statistically significant difference was observed in term of survival outcomes between the SIG and the LIG in pCR pts. OC-0429 Neoadjuvant chemoradiotherapy or 5x5 Gy followed by chemotherapy in rectal cancer: the RAPIDO trial C. Marijnen 1 , For the cooperative group of the RAPIDO trial 2 1 Leiden University Medical Center LUMC, Department of Radiotherapy, Leiden, The Netherlands Purpose or Objective Current standard for the most locally advanced rectal cancers is preoperative chemoradiotherapy (CRT), and, variably per institution, postoperative adjuvant chemotherapy. Short-course preoperative radiation with delayed surgery induces tumour downstaging in both randomized and observational studies. In the RAPIDO trial, the value of short-term preoperative radiotherapy with 5x5 Gy followed by neoadjuvant chemotherapy is investigated in a randomized fashion. Material and Methods Patients with rectal cancer with high risk features for systemic or local failure on magnetic resonance imaging were eligible. Randomization took place between a standard arm A : long course chemoradiotherapy followed