Endoscopic ultrasound-guided fiducial marker placement for image-guided proton beam therapy in pancreatic cancer: implications for positional accuracy and position management.

Authors

Kazunori Takeuchi, Takuya Ishikawa, Kentaro Yamao, Yasuyuki Mizutani, Tadashi Iida, Yoshihisa Takada, Masashi Tomida, Takeshi Yanagi, Yuta Shibamoto, Takahiro Toyama, Kenji Yamao, Makoto Narita, Reiko Ashida, Takeshi Yamamura, Hiroki Kawashima

Published in

Journal of radiation research. Sep 25, 2026. Epub Sep 25, 2026.

Abstract

High geometric precision is essential in proton beam therapy (PBT) for pancreatic cancer. This study evaluated inter-fraction positional accuracy during image-guided PBT using radiopaque surrogates and assessed endoscopic ultrasound-guided fiducial marker placement (EUS-FP). Patients with pancreatic cancer treated with PBT between 2020 and 2024 were retrospectively reviewed. The positional accuracy cohort included 58 patients with a radiopaque surrogate (fiducial marker group, n = 46; biliary stent group, n = 12). Major positional deviation was defined as a couch displacement ≥5 mm after bony alignment. Factors associated with major positional deviation were analyzed using generalized estimating equations. Oncologic outcomes were analyzed in patients with unresectable locally advanced (UR-LA) pancreatic cancer receiving concurrent chemoradiotherapy (n = 27). EUS-FP was technically successful in 45/46 patients (98%), with mild adverse events in 13%. Major positional deviation occurred in 18.5%, 30.9% and 11.2% of setups in the left-right, cranio-caudal and antero-posterior directions, respectively. Tumor location and disease status were independently associated with major positional deviation, whereas surrogate type was not. Pancreatic head tumors showed a higher risk than tail tumors, while UR-LA cases demonstrated greater positional stability. Overall survival from diagnosis did not differ significantly between surrogate groups; the median follow-up was 14.9 months. These findings indicate that positional deviation during PBT is primarily driven by tumor-related characteristics rather than the type of radiopaque surrogate used for image guidance. Although biliary stents may serve as radiopaque surrogates in selected cases, EUS-FP is a safe and reproducible technique enabling image-guided PBT.

PMID:
42786604
Bibliographic data and abstract were imported from PubMed on 25 Sep 2026.

Read full publication at:
Please sign in to see all details.

Stats

1-terrible, 9-excellent. How would you rate this publication? Sign in in to submit your rating.

Post a comment

You need to be signed in to post comments. You can sign in here.

Comments

There are no comments yet.