ESTRO 2020 Abstract Book

S589 ESTRO 2020

this interval is still lacking. Therefore, in this study we assess the physician and patient reported short-course radiotherapy-induced acute toxicity in the waiting period before surgery for rectal cancer. Material and Methods All rectal cancer patients referred to the Radiotherapy Department of UMC Utrecht for neoadjuvant SCRT-delay (5 times 5 Gy without immediate surgery) were asked to score low anterior resection syndrome (LARS) symptoms before, during and weekly after radiotherapy. Every week, participating patients were contacted by telephone by the physician or researcher to assess toxicity (dermatitis, diarrhea, fatigue, cystitis and urine incontinence according to CTCAE 4.0). Only descriptive statistics were applied. Results 20 patients (9 female, 11 male) were included. Median age was 61.5 years (IQR 53.0-69.7). 13 patients received SCRT- delay for intermediate risk rectal cancer, one patient for locally advanced rectal cancer unable to undergo neoadjuvant chemoradiation and 6 patients for oligometastatic disease (M1-scheme). Median interval to surgery was 8 weeks. The majority of patients did not experience dermatitis, fatigue, cystitis or urine incontinence during or after radiotherapy. A transient increase in CTCAE grade 2 or 3 diarrhea was seen 2-3 weeks after SCRT. LARS scores of 16 patients were available for analysis. 88% of patients experienced major LARS within 2 weeks following radiotherapy. Most reported complaints were frequency, urgency and re-evacuation within 1 hour. The majority of patients was free of complaints before they proceeded to surgery. No hospital admissions were recorded during the study period.

These results indicate that the SCRT-delay strategy is safe and well tolerated by patients. PO-1115 What’s the role of tumor regression grade (TRG) in rectal cancer: an istututional experience A. Guaineri 1 , L. Triggiani 1 , F. Frassine 1 , J. Imbrescia 1 , F. Barbera 1 , P. Vitali 1 , F. Terraneo 1 , L. Pegurri 1 , E. Ranghetti 1 , A. Taddeo 1 , S.M. Magrini 1 , M. Buglione 1 1 Spedali Civili di Brescia, Radiation Oncology, Brescia, Italy Purpose or Objective The neoadjuvant treatment with long-course radiotherapy and concomitant chemotherapy (NA-CRT) or with short- course radiotherapy followed by surgery is now the standard treatment in locally advanced rectal tumors. A parameter that allows us to have a degree of prediction of the response to neoadjuvant treatment is TRG (tumor regression grade), which is always included in the histopathological report and which defines the degree of tumor regression. In the literature TRG has shown to predict outcome after NACRT. The objective of this retrospective study is to confirm the prognostic value of the TRG, evaluating if there is a significant correlation with disease features and the main The TRG was evaluated in 133 patients with histological diagnosis of adenocarcinoma of the rectum using the Ryan classification system (0-No viable cancer cells, 1-Single cells or small groups of cancer cells, 2-Residual cancer outgrown by fibrosis, 3-many tumor cells with poor fibrosis/extensive residual neoplasia). The patients undergo,from May 2004 to April 2017, a neoadjuvant treatment with long-course radiotherapy associated with fluoropyrimidine chemotherapy and subsequently undergo surgery. Disease basal and after surgery characteristics were analyzed and related to TRG and OS, DFS, DSS, MFS and LRFS. (SPSS® 25.0). Results 133 patients were treated. Median age 64,5 (68%<70aa and 31,6%>70aa). Ninety-two patients (69.2%) hadcT3 disease, and 28 (21,1%) cT2; 10 patients hadcN1a, 42 cN1b (Tab1). After surgery the most patients were pT3(n=63, 51,1%), the other pT2 n=42(31,6%); 87 patients (65,4%) were pN0, 14 (10,5%) pN1a, 14 (10,5%) pN1b, 6 (4,5%) pN2a, 6 (4,5%) pN2b(Tab1. Staging before treatment was performed with TC and EUS (n=42), only TC (n=48), RMN (n=42). Chemotherapy was 5-FU in 126 cases and Capecitabine in 20 cases, 2 other. Median days between Rt and surgery were 46 days. For the 133 patients analyzed, 25 (18.8%) showed a TRG 3, 49 (36.8%) a TRG 2, 46 (34.6%) a TRG 1 and 13 (9.8%) a TRG 0. The TRG was statistically related to DFS (p <0.001), to MFS (p = 0.003) but not to LRFS (p = 0.85) and to DSS (p = 0.132),indeed patients bad responders (TRG 4) have a minor time to relapse locally and for distant metastasis. At the multivariate analysis only the TRG and the pathological stage were significantly correlated with DFS. The Cox regression (p = 0.033) showed an increased risk for relapse in patients with TRG 4 compared to good responders (HR 5.3) in relation to DFS. oncological outcomes. Material and Methods

Conclusion Diarrhea and LARS symptoms are most reported within 2-3 weeks following short course radiotherapy for rectal cancer, but these complaints recover before surgery. No grade >3 toxicity was seen in this limited patient group.