Patterns of Regional Failure after Pancreaticoduodenectomy in Patients with Distal Extrahepatic Cholangiocarcinoma: Suggestion of the Clinical Target Volume for Elective Nodal Irradiation

Aims: To evaluate the pattern of locoregional recurrence (LRR) after pancreaticoduodenectomy in patients with distal extrahepatic cholangiocarcinoma (DEHC) and to identify an optimal target volume for elective nodal irradiation. Materials and methods: We analysed the medical records of DEHC patients who underwent pancreaticoduodenectomy and had LRR between 1991 and 2015. Among these patients, 30 received adjuvant chemotherapy alone, 14 underwent radiotherapy with or without chemotherapy and 28 received no treatment. After reviewing computed tomography or magnetic resonance imaging scans, the sites of LRR were identified and mapped to the corresponding locations on the representative computed tomography images. Results: In total, 136 LRRs were identified in 72 patients from four institutions. Local recurrences were observed at 44 sites (32.4%): tumour bed in 15, choledochojejunostomy in 25 and pancreaticojejunostomy in four. Regional recurrences were observed at 92 sites (67.6%); the most common site was the portal vein area (n = 18), followed by the para-aortic area (n = 17). Based on the mapped plots of regional recurrence, a clinical target volume covering 90% of regional recurrences was generated using the appropriate margin for the vascular structures of the portal vein, celiac axis, superior mesenteric artery, left gastric artery and aorta. Conclusions: Given the pattern of LRR, we showed that the nodal clinical target volume based on vascular structures could appropriately cover high-risk regions of nodal involvement. These findings may help physicians construct a target volume in postoperative radiotherapy for DEHC patients undergoing pancreaticoduodenectomy.