Abstract Book

S797

ESTRO 37

Department of Oncology and Radiotherapy, Warsaw, Poland

feasible , well tolerated and has demonstrated efficacy as better outcome , compared to capecitabine & 3D-CRT alone, regarding upfront preoperative tx of pts with locally advanced rectal cancer. EP-1468 Endoscopic evaluation for radiation proctitis in patients receiving intermediate-dose radiotherapy J. Lee 1 , H. Hee Ji 2 , M. Byung So 3 , H. Sung Pil 4 , S. Sang Joon 5 , Y. Hong in 2 , P. Soo Jung 4 , K. Woong Sub 2 1 Inha University Hospital, Radiation Oncology, Incheon, Korea Republic of 2 Yonsei University College of Medicine, Department of Radiation Oncology, Seoul, Korea Republic of 3 Yonsei University College of Medicine, Department of Surgery, Seoul, Korea Republic of 4 Yonsei University College of Medicine, Division of Gastroenterology- Department of Internal Medicine, Seoul, Korea Republic of 5 Yonsei University College of Medicine, Division of Medical Oncology- Department of Internal Medicine, Seoul, Korea Republic of Purpose or Objective High-dose pelvic radiotherapy (RT) is known to be associated with chronic radiation proctitis (RP). However, the effects of intermediate radiation doses are unknown. We assessed the incidence of late clinical RP among patients with rectal cancer receiving intermediate-dose postoperative RT, as well as the role of early endoscopic abnormalities in predicting RP development. Material and Methods We retrospectively reviewed 153 patients with rectal cancer who received postoperative RT at a median dose of 54 Gy between 2005 and 2009 and who underwent endoscopic examination within 12 months thereafter. Endoscopic RP was assessed using the Vienna rectoscopy score (VRS) throughout endoscopy. Late clinical RP toxicity was evaluated, and its correlation with endoscopic RP was assessed. Results All patients underwent endoscopic examination at 9 months (median) after postoperative pelvic RT. Endoscopic RP was detected in 45 patients (29.4%); the predominant patterns were telangiectasia and congested mucosa. During the follow-up period (median, 88 months), 29 patients (19.0%) experienced late clinical RP; only 3 patients (2.0%) had grade 3 or above. The VRS predicted the development of late clinical RP as well as its cumulative incidence (p < 0.001). Endoscopic evidence of telangiectasia was significantly associated with the development of late clinical RP (p < 0.001). Conclusion Early endoscopic findings using VRS are useful for predicting the possibility of late clinical RP, although the incidence of severe cases in our study was low. Patients with endoscopic abnormalities should be followed closely owing to their susceptibility to clinical RP. EP-1469 Impact of pelvis irradiation on toxicity of further oxaliplatin-based chemotherapy in rectal cancer M. Spalek 1 , W. Michalski 2 , K. Bujko 1 , L. Wyrwicz 3 1 The Maria Sklodowska-Curie Memorial Cancer Center, Department of Radiotherapy I, Warsaw, Poland 2 The Maria Sklodowska-Curie Memorial Cancer Center, Laboratory of Bioinformatics and Biostatistics, Warsaw, Poland 3 The Maria Sklodowska-Curie Memorial Cancer Center,

Purpose or Objective Radiotherapy is used in the neoadjuvant setting in the majority of rectal cancer patients, while its effect on overall survival is limited mostly to patients with threatened resection margin. Preoperative pelvic irradiation might damage bone marrow. In consequence, relative dose intensity (RDI) and efficacy of further adjuvant or palliative chemotherapy might be reduced. The aim of the study was to assess whether preoperative pelvis irradiation may influence on the tolerance of further oxaliplatin-based chemotherapy. Material and Methods We have performed the cohort analysis of patients with adenocarcinoma of rectum or colon receiving FOLFOX-4 chemotherapy in adjuvant or palliative setting between 2011-2016. Oxaliplatin RDI within 8 weeks from the beginning of chemotherapy was calculated for each patient. The major factors, which can reduce oxaliplatin RDI, were analyzed independently (hematological toxicity, neurological toxicity, an occurrence of hypersensitivity reactions to oxaliplatin). The data regarding the first disruption of oxaliplatin dose within all planned courses of FOLFOX-4 was also collected. Results 220 patients met eligibility criteria. 41 of them received neoadjuvant radio(chemo)therapy (study group), the remaining 179 patients were assigned to control group (n=179). Median RDI did not differ significantly between irradiated (95.908 %) and non-irradiated patients (96.154 %, p=0.794). There were no statistically significant differences in observed oxaliplatin-related toxicities. The median time between the start of chemotherapy and the first disruption of oxaliplatin administration was also not statistically different between the two groups (p=0.156).

Fig. 1. Estimated mean time to the first disruption of oxaliplatin administration

Conclusion An impact of preoperative radio(chemo)therapy on RDI or tolerance of FOLFOX was not found in rectal cancer. EP-1470 Neoadjuvant VMAT radiochemotherapy with a SIB Compared to standard Chemoradiation for LARC N. Jankarashvili 1 , M. Topeshashvili 1 , L. Turkiashvili 2 , B. Metonidze 3 , E. Dgebuadze 4 , T. Melkadze 5 , I. Kiladze 6 , G. Korakhashvili 2 1 Research Institute of Clinical Medicine, Radiation Oncology Department, Tbilisi, Georgia 2 Tbilisi Cancer Center, Surgical Oncology/Department of Surgery, Tbilisi, Georgia 3 Tbilisi Cancer Center, Surgical Oncology / Department of Surgery, Tbilisi, Georgia 4 Tbilisi Cancer Center, Chemoherapy Department,