Abstract Book

S792

ESTRO 37

complications. Three pts (23%) developed acute G3 or greater hematologic toxicity (1 anemia and 2 neutropenia), 1 pt developed acute G3 gastrointestinal pain, no further G3 or greater nonhematologic toxicity was observed. One patient developed G2 gastric ulcer and G2 gastric haemorrhage that were medically managed. Late G3 or greater toxicities were not observed Conclusion Induction CHT regimen combined with LDR used as a chemo-enhancer and SBRT in three fractions resulted in a low rate of side effects. We wait for enrolment conclusion to report efficacy results EP-1458 Radiotherapy for elderly patients with esophageal squamous cell carcinoma: a SEER based analysis J. Zhang 1 , M. Li 1 , H. Gong 1 , W. Huang 1 , B. Li 1 1 Shandong Cancer Hospital, Radiation oncology, Jinan, China Purpose or Objective Esophageal squamous cell carcinoma (ESCC) is a common neoplasm in China and most patients would receive radiotherapy (RT) in treatment. The elderly ESCC patients have relatively low RT tolerance and the determinants of their prognosis are more complex. To assess the benefit of RT and investigate the prognosis associate clinical variables for elderly ESCC, we performed this analysis based on Surveillance, Epidemiology, and End Results (SEER) database. Material and Methods All the accessible clinical informations of included patients, which must be ESCC diagnosed at the age elder than 65 and survived more than 3 months were exported using SEER*Stat. The overall included patients were further sub- grouped according to stratified factors and propensity score matching were em ployed when necessary .The log rank test and cox regression model were used for survival analysis and the Kaplan–Meier plots for stratified comparisons.We evaluated the predict model by cross-validation and Totally 9663 patients were included, among whom 6698 had documented RT history. For all the ESCC patients, RT did not show significantly benefit compared with non- RT(HR=0.982, p=0.49),while in distant stage group, the patients with RT have better prognosis(HR=0.798, p= 1.9e-5).The surgery group (n=1835) survived longer (median OS: 17 months vs 11 months) than non- surgery,but RT could not provide additional survival benefit (median OS: 16 months vs 18 months) for surgery patients. Patients received pre-operative RT had significantly prolonged OS compared with surgery alone or with post-operative RT patients (median OS: 20 month vs 14 month; HR=0.644,p= 6e-10), and the trend remained after adjustment by other clinical variables. The multiple cox regression model involved variables including radiation sequence,surgery status, stage, scatological grade and diagnosis time. The calibrated nomogram here could effectively predict the prognosis of elderly ESCC patients. Conclusion RT showed survival benefits for distant stage of elderly ESCC and pre-operative RT could significantly prolong OS, while RT failed to show benefits in other comparisons and multi-variable analysis.Oncologist should carefully adopted nomogram for visualization. All the analysis were conducted in R. Results

trade-off the benefits and side effects of RT for elderly ESCC patients.

Electronic Poster: Clinical track: Lower GI (colon, rectum, anus)

EP-1459 Meta-analysis comparing gastrointestinal toxicity among radiotherapy techniques in rectal cancer C.W. Wee 1 , H.C. Kang 1 , H.G. Wu 1 , E.K. Chie 1 , J.M. Park 1 , J.I. Kim 1 , C.M. Huang 2 , J.Y. Wang 3 , S.Y. Ng 4 , K.A. Goodman 5 1 Seoul National University Hospital, Department of Radiation Oncology, Seoul, Korea Republic of 2 Kaohsiung Medical University Hospital, Department of Radiation Oncology, Taiwan, Taiwan 3 Kaohsiung Medical University Hospital, Department of Surgery, Taiwan, Taiwan 4 Alfred Health Radiation Oncology, Department of Radiation Oncology, Victoria, Australia 5 University of Colorado Denver School of Medicine, Department of Radiation Oncology, Aurora, USA Purpose or Objective To compare the acute gastrointestinal (GI) toxicity profiles of intensity-modulated radiotherapy (IMRT) and 3-dimensional conformal radiotherapy (3DCRT) in locally advanced rectal cancer patients treated with neoadjuvant concurrent chemoradiation (CCRT), using meta-analysis. Material and Methods Literature search was performed with PubMed and EMBASE from inception to March 2017. Studies comparing GI toxicities between IMRT vs. 3DCRT in rectal cancers were included. The odd ratios (ORs) were calculated, and a random-effects model was used. Results Six retrospective studies with a total of 859 patients were analyzed. Median RT doses were 50–50.4 Gy in all studies, and almost all patients received neoadjuvant CCRT. IMRT, compared to 3DCRT significantly reduced acute grade 2 or higher overall GI toxicity, diarrhea, and proctitis with ORs of 0.38 (95% confidence interval [CI] 0.26–0.54), 0.32 (95% CI 0.20–0.50), and 0.60 (95% CI 0.42–0.86), respectively. IMRT also significantly reduced acute grade 3 or higher proctitis compared to 3DCRT (OR 0.24, 95% CI 0.07–0.84). However, there was no significant difference in grade 3 or higher overall GI toxicity (OR 0.51, 95% CI 0.20–1.31, p =0.16) and diarrhea (OR 0.56, 95% CI 0.21–1.51, p =0.25). The incidence of grade 3 or higher overall GI toxicity (2.6% vs. 8.9%) and diarrhea (2.2% vs. 6.3%) were both lower in the IMRT group compared to 3DCRT. No significant heterogeneity or publication bias was detected. Conclusion IMRT should be recommended in rectal cancer patients treated with neoadjuvant CCRT in order to reduce grade 2 or higher GI toxicity. For accurate comparison of grade 3 or higher GI toxicity among IMRT and 3DCRT, further accumulation of data is necessary. EP-1460 A systematic review comparing radiation toxicity after various endorectal radiation techniques A. Verrijssen 1 , T. Opbroek 2 , F. Verhaegen 3 , M. Bellezzo 3 , G. Paiva Fonseca 3 , E. Van Limbergen 1 , M. Berbee 1 1 MAASTRO Clinic, Radiation Oncology, Maastricht, The Netherlands