Study of inter-fractional variations and adaptive radiotherapy in pancreatic cancer
YANG Cheng-liang*, X. Allen Li, WANG Jian-hua, LI Ding-jie, MAO Rong-hu
*Department of Radiation Oncology, Henan Cancer Hospital, Affiliated Cancer Hospital of Zhengzhou University, Zhengzhou 450003,China Corresponding author:WANG Jian-hua
Abstract：Objective To quantitatively characterize the inter-fractional anatomy variations and advantages of dosimetry for the adaptive radiotherapy in pancreatic cancer. Methods A total of 226 daily CT images acquired from 10 patients with pancreatic cancer treated with image-guided radiotherapy were analyzed retrospectively. Targets and organs at risk (OARs) were delineated by the atlas-based automatic segmentation and modified by the skilled physician. Various parameters, including the center of mass (COM) distance, the maximal overlap ratio (MOR) and the Dice coefficient (DC), were used to quantify the inter-fractional organ displacement and deformation. The adaptive radiation therapy (ART) was applied to handle the daily CT images. The dose distributions parameters from the ART plan were compared with those from the repositioning plan. Results The inter-fractional anatomy variations of pancreas head were obvious in the pancreatic cancer irradiation. The mean COM distance, MOR and DC of pancreas head after the bony or soft tissue alignment and registration was (7.8±1.3) mm,(87.2±8.4)% and (77.2±7.9)% respectively. Compared with the repositioning plan, the ART plan had better target coverage and OARs sparing. For example, the mean V100 of PTV was improved from (93.32±2.89)% for repositioning plan to (96.03±1.42)% for ART plan with t=2.79,P=0.008 and the mean V50.4 for duodenum was reduced from (43.4±12.71)% for the repositioning plan to (15.6±6.25)% for the ART plan with t=3.52,P=0.000. Conclusions The ART can effectively account for the obvious inter-fractional anatomy variations in pancreatic cancer irradiation and be used to escalate the radiotherapy dose for the pancreatic cancer, which will lead to a promising higher local control rate.
YANG Cheng-liang*,X. Allen Li,WANG Jian-hua et al. Study of inter-fractional variations and adaptive radiotherapy in pancreatic cancer[J]. Chinese Journal of Radiation Oncology, 2012, 21(3): 263-266.
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2012, Vol. 21 
