Pancreatic Tumor Motion on a Single Planning 4D-CT Does Not Correlate With Intrafraction Tumor Motion During Treatment

Abstract

Purpose:To quantify pancreas tumor motion on both a planning 4D-CT and during a single fraction treatment using the CyberKnife linear accelerator and Synchrony respiratory tracking software, and to investigate whether a single 4D-CT study is reliable for determining radiation treatment margins for patients with locally advanced pancreas cancer. Methods and Materials: Twenty patients underwent fiducial placement, biphasic pancreatic protocol CT scan and 4D-CT scan in the treatment position while free-breathing. Patients were then treated with a single 25 Gy fraction of stereotactic body radiotherapy. Predicted pancreas motion in the superior-inferior (SI), left-right (LR), and anterior-posterior (AP) directions was calculated from the maximum inspiration and maximum expiration 4D-CT scan. For CyberKnife treatments, mean respiratory cycle motion and maximum respiratory cycle motion was determined in the SI, LR, and AP directions. Results: The range of centroid movement based on 4D-CT in the SI, LR, and AP directions were 0.9 to 28.8 mm, 0.1 to 13.7 mm, and 0.2 to 7.6 mm, respectively. During CyberKnife treatment, in the SI direction, the mean motion of the centroid ranged from 0.5 to 12.7 mm. In the LR direction, the mean motion range was 0.4 to 9.4 mm. In the AP direction, the mean motion range was 0.6 to 5.5 mm. The maximum range of movement (mean) during CyberKnife treatment in the SI, LR, and AP directions were 4.5 to 48.8 mm (mean 20.8 mm), 1.5 to 41.3 mm (mean 11.3 mm), and 1.6 to 68.1 mm (mean 13.4 mm), respectively. Neither the maximum or mean motion correlated with the 4D-CT movement. Conclusions: There is substantial respiratory associated motion of pancreatic tumors. The 4D-CT planning scans cannot accurately predict the movement of pancreatic tumors during actual treatment on CyberKnife.

Image-Guided Stereotactic Radiosurgery for Locally Advanced Pancreatic Adenocarcinoma Results of First 85 Patients

“…Although retroperitoneally located, the movements of the pancreas with each respiration cycle are considerable, ranging from 1.1 to 2 cm in different direction. 35 Synchrony®, which utilizes respiratory gating technology, can account for such movements thereby delivering the high dose to the target without much radiation exposure to adjacent viscera. SRS can deliver 25.5 Gy dose in 1 day.…”

Stereotactic radiotherapy in the liver hilum

“…Information of high resolution MRI and CT scans is recommended for SBRT planning. In this context, 4D imaging including PET or PET/CT may play an increasing role [24].…”

Stereotactic body radiotherapy for the pancreas: a critical review for the medical oncologist

“…Despite limiting variability using custom-molds, mechanical respiration can also lead to changes in the position of the pancreas, often between one and three centimeters, causing variability in targeting (16,17). In order to account for these changes, patients are simulated with 4-dimentional computer tomography (4D-CT) simulation (18,19).…”