Abstract
PurposeWe investigated the movement characteristics of pancreas and the clinical accuracy of tracking pancreas with the Synchrony Respiratory Tracking System (SRTS) during the CyberKnife treatment. These data provide a clinical data basis for the expansion margins of pancreatic tumor target.Methods and MaterialsForty-two patients with pancreatic cancer treated by CyberKnife were retrospectively studied. The pancreatic displacement calculated from the x-ray images collected during the time interval between two consecutive movements constituted a data set.ResultsThe total mean motion amplitudes and standard deviations of pancreatic tumors in SI, LR, AP, and radial directions were 3.66 ± 1.71 mm, 0.97 ± 0.62 mm, 1.52 ± 1.02 mm, and 1.36 ± 0.49 mm, respectively. The overall mean correlation errors and standard deviations were 0.82 ± 0.46 mm, 0.47 ± 0.33 mm, 0.41 ± 0.24 mm, and 0.98 ± 0.37 mm, respectively. The overall mean prediction errors and standard deviations were 0.57 ± 0.14 mm, 0.62 ± 0.28 mm, 0.39 ± 0.17 mm, and 1.58 ± 0.36 mm, respectively. The correlation errors and prediction errors of pancreatic tumors at different anatomical positions in SI, LR, and AP directions were statistically significant (p < 0.05).ConclusionsThe tumor motion amplitude, the tumor location, and the treatment time are the main factors affecting the tracking accuracy. The pancreatic tumors at different anatomical locations should be treated differently to ensure sufficient dose coverage of the pancreatic target area.
Highlights
Pancreatic cancer is one of the most aggressive tumors, and there is almost no effective treatment method at present
This study aims to answer three key clinical questions: [1] motion characteristics of pancreatic tumors under free breathing; [2] the accuracy and related factors of tracking pancreas by the CyberKnife SRT system; and [3] the expansion margin of the pancreatic target is guided by the movement characteristics of pancreas and the tracking accuracy of the SRT system
We studied the internal motions and the tracking accuracies of 42 patients with pancreatic cancer treated with CyberKnife and analyzed the tracking accuracies of different anatomical locations
Summary
Pancreatic cancer is one of the most aggressive tumors, and there is almost no effective treatment method at present. Current evidence suggests that increasing the dose of SBRT may further improve patient outcomes [4]. The increase of dose is limited by toxicity of surrounding normal organs. During SBRT treatment of pancreas, the surrounding normal organs, stomach, and duodenum [5] are highly sensitive to radiation and adjacent to the pancreas. Digestion, and heartbeat, the boundary between the tumor and nearby organs is blurred. This internal target movement may lead to insufficient local dose of tumor and excessive dose of normal organs at risk (OARs) [6]
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