ESTRO 38 Abstract book

S785 ESTRO 38

2016 were reviewed. Waiting time was defined as interval between the pathological diagnosed date until the first fraction of radiation delivered date. Referring pathway interval was defined as time from the pathological diagnosed date to the first date of radiation oncologist and patient meeting. Internal radiation oncology division interval was defined as time from the first date of radiation oncologist and patient meeting to the first fraction of radiation delivered date. Results The median waiting time was 41 days (IQR 25, 56.2); referring pathway interval 27 days (IQR 13, 44), internal radiation oncology division interval 11 days (IQR 8, 16). The estimated 5-year local control and overall survival were 76.8% (95%CI 68.4-86.2) and 61.7% (95%CI 54-70.5), respectively. In patients who had local recurrence, the median waiting time was 57 days (IQR 40, 78.8) compared with 42 days (IQR 27, 64) in patients who did not have (P- value 0.014). According to waiting time ≤35 days, 36-56 days and >56 days, the estimated 5-year local control were 90%, 74%, 60% respectively as shows in figure 1. Using waiting time ≤35 days as the reference group, the HR of local recurrence were 4.49 (95%CI 1.2-16.83, P-value 0.026) with waiting time 36-56 days and 9.05 (95%CI 2.23- 36.79, P-value 0.002) with waiting time >56 days. Multivariate analysis showed that ECOG score, radiation dose and surgery were associated with local recurrence. We did not found the relationship between waiting time and overall survival.

receiving the greatest dose) was associated with risk of G2+ (p<0.01) and G3+ (p=0.048) GD AEs, as was BED 3 (<0.01 and <0.01). Conclusion For patients with pCCA receiving CRT and HDR BT, higher BT GD D0.1 cc and higher BED 3 were both associated with an increased risk of GD AEs.

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

EP-1446 Clinical efficacy and safety of consolidative radiotherapy in the maintenance treatment of mCRC Z. LIN 1 , Z. Danyang 1 , Y. Dandan 1 , W. Jing 1 , Z. Tao 1 1 Union Hospital- Tongji Medical College- Huazhong University of Science and Technology, Cancer Center, Wuhan, China Purpose or Objective For metastatic colorectal cancer (mCRC) patients responding to induction therapy, maintenance treatment prolongs the progression-free survival (PFS) while maintains quality of life. The purpose of this study was to evaluate the clinical efficacy and safety of local consolidative radiotherapy in maintenance treatment for patients with limited mCRC. Material and Methods Between October 2011 and June 2017, 19 mCRC patients (6 males and 13 females) who achieved a partial response (PR) or stable disease (SD) to induction chemotherapy and received subsequent consolidative radiotherapy of metastatic lesions and maintenance treatment were retrospectively enrolled. Results The median age was 57 years (range 33 to 70). Nine patients received local consolidative radiotherapy to liver (median BED=66.3 Gy), 6 patients to pelvis (median BED=60.0 Gy), 5 to lung (median BED=78.0 Gy), and others. The incidence of LR failure was 5.3% and 21.1% at 1 and 2 years, respectively. The incidence of distant failure was 47.4% and 68.4% at 1 and 2 years, respectively. The median OS was 35.5 months (95% CI, 13.41-57.59), and median PFS was 12.4 months (95% CI, 1.77-23.03). Main grade 3 or 4 toxicities were leukopenia (n = 2, 10.5%). The most common adverse events were leukopenia (n = 14, 73.7%), thrombocytopenia (n = 7, 36.8%), anemia (n = 5, 26.3%), transaminase elevation (n = 5, 26.3%), and diarrhea (n = 2, 10.5%). Conclusion Consolidative radiotherapy prior to maintenance treatment improved local control and prognosis of mCRC patients with acceptable toxicities. Despite the limited data of present study, it could be contemplated as an effective therapeutic alternative in selected patients. EP-1447 Effect of waiting time to radiation on local control and overall survival in rectal cancer A. Tangkananan 1 , R. Jiratrachu 1 1 Prince of Songkla University, Division of Radiation Oncology- Department of Radiology- Faculty of Medicine, Songkla, Thailand Purpose or Objective To evaluate the effect of waiting time to radiation after diagnosis on local control and overall survival in locally staged rectal cancer patients, and to show the cause of prolonged waiting time: referring pathway or internal radiation oncology division. Material and Methods A data of 275 patients with locally staged adenocarcinoma of rectum who were treated with radiation as neoadjuvant concurrent chemoradiation or definite concurrent chemoradiation between January 2011 and December

Figure 1 Estimated local control by waiting time Conclusion Prolonged waiting time to radiation was strongly associated with poorly local control but not overall survival. The main duration of waiting time was referring pathway interval. EP-1448 Preoperative VMAT with simultaneous integrated boost for locally advanced distal rectal cancer Y. Yang 1 , Q. Liu 2 , P. Zhao 1 , J. Qian 1 , Q. Peng 1 , Y. Zhu 1 , L. Feng 3 1 the Second Affiliated Hospital of Soochow Universit, Radiotherapy & Oncology, Suzhou, China ; 2 Beijing Luhe Hospital Affiliated to Capital Medical University, Radiation Oncology, Beijing, China ; 3 Chinese PLA General Hospital, Radiation Oncology, Beijing, China Purpose or Objective The aim of this study was to evaluate the safety and clinical efficacy of a combined preoperative regimen consisting of volumetric modulated arc therapy-