Background  Radiotherapy is an important local treatment for locally advanced and metastatic pancreatic cancer, but the optimal dose fractionation mode for radical purpose is not yet determined.

  Objective  To evaluate clinical outcomes and severe adverse events in hypofractionated simultaneous integrated boost (SIB) Helical Tomotherapy with an intent to cure patients with locally advanced, inoperable and metastatic pancreatic cancer, so as to develop a novel dose-fraction model for these entities.

  Methods  From January 2011 to April 2014, 19 patients with pathologically confirmed, locally advanced, inoperable pancreatic adenocarcinoma and metastatic pancreatic cancer, who received hypofractionated SIB radiotherapy from planning target volume (PTV) to gross target volume (GTV) using Helical Tomotherapy, were enrolled in this study. Radiation therapy was directed to the primary tumor and metastatic lesions with a margin of 0.5 to 0.8 cm in axial plane and 0.5 to 1.0 cm in longitudinal plane. Primary end points included tumor local control, determination of dose-limiting toxicity and limitation of dose and volume, and the secondary end points included progression free survival and overall survival. The biological equivalent doses (BED₁₀) were evaluated when α/β was equal to 10.

  Results  With a median follow-up of 10.7 months, 19 patients with locally advanced, inoperable and metastatic pancreatic cancer were treated with hypofractionatd SIB using Helical Tomotherapy. The prescribed dose-fraction was 50-60 Gy/17-23 f with the median BED₁₀ of 81 Gy (range, 78-90 Gy). The tumor local control rate was 84%. The median local progression-free survival (LPFS) and median overall survival (mOS) were 8.1 months (95% CI: 5.8-10.5 months) and 10.7 months (95% CI: 3.4-17.9 months) for the entities, respectively. The median maximum dose (Dmax) exposed on stomach was 56 Gy (range: 33-69 Gy), while on duodenum was 52 Gy (range: 22-59 Gy). The incidence of dose limited toxicity (DLT) of duodenal hemorrhage was 5% (1/19). The corresponding duodenum dose-volume limitations at BED₁₀ were 0.03 cm³ at 70 Gy, 0.50 cm³ at 63 Gy, 2.62 cm³ at 55 Gy and 6.33 cm³ at 48 Gy, respectively.

  Conclusion  Hypofractionated SIB radiotherapy using Helical Tomotherapy is a well tolerable and effective way to treat locally advanced, inoperable and metastatic pancreatic cancer. The hypofractionated SIB models need to be warranted in further study.