Postoperative recurrence patterns and anatomy-stratified clinical target volume delineation in pancreatic cancer.

objectivesThis study aims to characterize postoperative recurrence patterns and anatomical distribution in patients with pancreatic cancer within the framework of extrapancreatic neural tract anatomy. Based on the observed recurrence sites, we propose stratified clinical target volume (CTV) delineation recommendations for postoperative adjuvant radiotherapy.

methodsWe retrospectively analysed 352 patients who underwent resection for pancreatic adenocarcinoma and recorded the sites of initial postoperative recurrence. Recurrence foci were reconstructed according to adjacent anatomical structures and mapped onto reference computed tomography images of the pancreatic head and of the body/tail. Spatial distances and distribution relative to major vessels were measured to define vessel-anchored CTV extension ranges for different primary tumour locations. These ranges were compared with the delineation recommendations of RTOG 0848 and the NRG consensus guidelines.

resultsRecurrence occurred in 285 patients (81%), with 187 head tumours and 98 body/tail tumours. Regional failures clustered along a limited number of extrapancreatic plexus pathways. In both head and body/tail tumours, more than four fifths of plexus-related recurrences arose along a pancreatic head plexus II (PLph II)/ superior mesenteric artery (SMA) plexus (PLsma)–celiac axis (CA) plexus (PLce) continuum centred on the axis between the SMA and CA, with a periaortic neurovascular corridor representing the caudal extension of this pathway. We propose a CTV strategy comprising a 0.7 cm margin around the CA, an approximately 1.0 cm margin around the portal vein (PV), common hepatic artery (CHA) and SMA, and an asymmetric periaortic expansion with 1.5 cm anteriorly and to the right, 1.0 cm to the left, and the posterior border confined to the anterior vertebral margin. For pancreatic head tumours, these margins are integrated into a CTV-based “Triangle Volume (TV)” that extends from the PV/CHA–SMA–CA triangle back to the periaortic corridor. For body and tail tumours, the CTV prioritises coverage of the CA–SMA–proximal periaortic neurovascular corridor while avoiding routine inclusion of the distal splenic artery and splenic hilum.

conclusionsVessel-anchored mapping validates the TV framework for pancreatic head tumours and provides quantitative, anatomy-stratified CTV recommendations for pancreatic head and body/tail primaries in the adjuvant setting.