ESTRO 2021 Abstract Book

S675

ESTRO 2021

Conclusion Use of CXB as part or all of an organ preservation strategy in rectal cancer provides acceptable rates of local control. These results compare favourably with other single institution series. The results of the randomised OPERA trial to further define the role of CXB are awaited with interest. PD-0840 Preoperative chemoradiotherapy in older patients with rectal Cancer: a multicenter phase II trial W. Liu 1 , Y. Tang 1 , J. Jin 2 , N. Li 3 , J. Wang 4 , Y. Cheng 4 , S. Wang 1 , Y. Li 1 , X. Wang 5 1 National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Radiation Oncology, Beijing, China; 2 Shenzhen Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Radiatioin oncology, Shenzhen, China; 3 Shenzhen Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Radiation Oncology, Shenzhen, China; 4 The Fourth Hospital of Hebei Medical University, Radiation Oncology, Shijiazhuang, China; 5 National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Colorectal Surgery, Beijing, China Purpose or Objective The purpose of this study was to evaluate the safety and efficacy of preoperative concurrent chemoradiotherapy (preCRT) for intermediate or locally advanced rectal cancer in older people who were classified as “fit” by Comprehensive geriatric assessment (CGA). Materials and Methods A single arm, multicenter, phase II trial was designed. The eligible patients for this study were aged 70 years or above and fit (SIOG1) evaluated by CGA that met the standard of intermediate or locally advanced risk category. The primary endpoint was 2-year DFS. Patients were scheduled to receive preCRT (50 Gy) with Raltitrexed ( 3 mg/m 2 on d1 and d22 ). Qualitative and quantitative variables were described using descriptive statistics. Survival result was evaluated by Kaplan-Meier method. Sample size consideration: since the recruitment period and minimum follow-up period covered a period of 24 months, we estimated that 51 patients were required to test the hypothesis that the 2-year DFS was equal to or greater than 78%, with 80% power, and to reject the hypothesis that the 2-year DFS rate was less than 63% at a significance level of 5% (one sided). Taking into consideration that 5% of patients may be lost for follow-up, and 20% of patients may refuse surgery, a total of 68 patients were expected to be included in the study.