Stereotactic body radiotherapy (SBRT) with CyberKnife for unresectable pancreatic tumor is a relatively new treatment option made available because of significant improvements in diagnostic imaging and radiation delivery techniques. Different from the conventional radiotherapy, radiation dose is delivered in fewer fractions and higher fractional doses in SBRT. Gurka (1) reported that 14 patients received SBRT with prescription dose of 25 Gy in five fractions with biologically equivalent doses (BED) of α/β=10 in correspondence to 37.5Gy. Grade 1 to 2 gastrointestinal toxicity (no grade 3 or 4 radiation-related toxicities) was observed two weeks after treatment. Two patients had a partial response, and 12 patients were with stable diseases. In the previous dose escalation study, a single fraction up to15 Gy, 20 Gy, 25 Gy which is an equivalent BED10 to 37.5 Gy, 60 Gy, 87.5 Gy respectively is recommended by Koong AC (2) and his team. Even though the local control rate is 100%, the follow up is short and the sample size of 15 patients is relatively small. Moreover, the late toxicity is not investigated. And with single fraction scheme, higher late gastrointestinal (GI) toxicities were reported (2,3,4). In the meanwhile, investigators (5, 6) from South Korea examined that a Dmax of 35Gy and 38Gy in 3 fractions (BED10 to 75.8Gy and 86.1Gy) of SBRT correlated with a 5% and 10% rate of grade 3 of gastroduodenal toxicity for abdominal malignant tumor, respectively.