Mapping of local recurrence after pancreaticoduodenectomy for distal extrahepatic cholangiocarcinoma: implications for adjuvant radiotherapy

Abstract

Objective: To generate a map of local recurrences after pancreaticoduodenectomy (PD) for patients with distal extrahepatic cholangiocarcinoma (DEHC) and to evaluate the adequate target volume coverage encompassing the majority of local recurrences when the clinical target volume (CTV) for pancreatic cancer was applied. Methods: We retrospectively reviewed the records of DEHC patients who underwent pancreaticoduodenectomy and had postoperative CT scans acquired between 1991 and 2015 available. The sites of local recurrence were delineated on individual CT scans, and then, mapping was manually performed onto template CT images. Coverage of each site of local recurrence was evaluated by applying the CTV defined according to Radiation Therapy Oncology Group (RTOG) consensus guidelines (CTVRTOG) for target delineation in the postoperative treatment of pancreatic head cancer. Results: Of the 99 patients, 36 patients had a total of 62 local relapses identifiable by postoperative CT scans; the relapses were the most frequent in the choledochojejunostomy (CJ) site, 11 sites (17.7%); para-aortic area, 10 sites (16.1%), superior mesenteric artery area, 10 sites (16.1%): and portal vein area, 9 sites (14.5%). 21 sites (33.9%) were not covered by the CTVRTOG, and the most common site of local recurrence outside the CTVRTOG was the CJ site. Conclusion: When mapping of local relapses was evaluated according to the CTVRTOG, the choledochojejunostomy site was identified as a high-risk area of local recurrence but was insufficiently covered within the CTVRTOG, These findings may help construct a target volume for postoperative radiotherapy in DEHC. Advances in knowledge: Mapping local recurrences can aid in defining appropriate target volume for postoperative radiotherapy in DEHC.