Limited Role for Biliary Stent as Surrogate Fiducial Marker in Pancreatic Cancer: Stent and Intratumoral Fiducials Compared

Abstract

For respiratory-induced motion, the mean ΔMM is small, but for individual patients the absolute difference can be >4 mm. For interfractional position variations, a stent is, on average, a better surrogate fiducial than bony anatomy, but large PTV margins would still be required. Therefore, intratumoral fiducials are recommended for online setup verification for all pancreatic patients scheduled for radiation therapy, including patients with a biliary stent.

Dosimetric effects of anatomical changes during fractionated photon radiation therapy in pancreatic cancer patients

“…Interfractional position variation of the target relative to the bony anatomy can be considerable in pancreatic cancer patients;7, 8, 9 in an earlier study, we found in 13 patients a three‐dimensional vector displacement of >10 mm in 116 out of 300 fractions 10. Intratumoral fiducial markers may be used for daily position verification to mitigate this positional uncertainty.…”

Modeling Pancreatic Tumor Motion Using 4-Dimensional Computed Tomography and Surrogate Markers

“…However, they also observed that even if the stent indicated tumor position better than bony anatomy, its risk of migration is higher than that of the fiducial (28).…”

Dosimetric Advantages of Midventilation Compared With Internal Target Volume for Radiation Therapy of Pancreatic Cancer

“…The size and location of the gross tumor volumes (GTVs) in the pancreas are given in Table 1. All patients (mean age, 65 years; range, 46-79 years), had received 2 to 4 intratumoral fiducials placed under endoscopic ultrasound guidance for daily position verification (2,4,16). The respiratory motion was measured using the 4DCT (LightSpeed RT16 system, General Electric Company, Waukesha, WI) consisting of 10 phase scans divided over the respiratory cycle.…”

“…Pancreatic tumors can show large interfractional position variation and large, mainly respiratory-induced, intrafractional motion (2,3). The interfractional position variation can be accounted for by online position verification using daily cone beam computed tomography (CBCT) scans registered to a reference scan, which is most effective when based on intratumoral fiducials (2,4), consequently reducing the target volume.…”