114 Background: Surgery is the standard of care for stage I esophageal squamous cell carcinoma. However, definitive chemoradiothearpy (CRT) is optional treatment which can preserve organ function with cure. The aim of this study was to investigate what factors have influence patients(pts)’ decision on the treatment, surgery or CRT. Methods: JCOG0502 is a randomized controlled trial comparing surgery to CRT. Sufficient information about both treatments was provided for pts before enrollment. Pts who declined to participate in randomized part can choose a preferred treatment and join a non-randomized part of JCOG0502. Between Dec 2006 and Feb 2013, 379 pts were enrolled to JCOG0502 from 37 institutions of Japan Clinical Oncology Group. Among those, 368 pts who enrolled to non-randomized part were analyzed. Clinical baseline data, social data and doctor’s preference which was not mandatory informed to patients were collected on the case report forms and compared between surgery arm and CRT arm. Preference of doctors for each pt was divided into three categories, A: “surgery is preferred”, B: “either is adequate” and C: “CRT is preferred”. This trial was registered as UMIN000000551. Logistic regression were performed to evaluate the influence of each factors. Results: Of the 368 pts, 209 pts chose surgery with their own intention, while 159 pts chose CRT. There were no differences on baseline clinical characteristics between two groups except median age (Surgery: CRT = 62:65 years). Multivariate logistic regression analyses showed that >=65 years (vs<65) (OR 2.04, p=0.006), male (vs female) (OR 2.10, p=0.043), multi-focal primary (vs single) (OR 2.76, p=0.013), status of patient’s children (vs presence of children) (absence of children: OR 2.27, p=0.034) (unknown: OR 4.422, p=0.13), and B or C category of preference of the doctor (vs A) (B:OR 11.67, p<0.001)(C:HR 29.64, p<0.001) were associated with selection of CRT. Conclusions: Older age, male, multifocal primary, absence of children and doctor’s preference are independent factor to choose CRT. Doctor’s preference to each pt was the strongest factor on decision making of patients.