Outcome of resectable distal cholangiocarcinoma in a single-centre Western patient cohort: comparison of the 7th and 8th edition of the UICC/AJCC TNM classification

BACKGROUND AND PURPOSE: Distal cholangiocarcinoma (CCA) is a rare malignancy with poor prognosis, even after surgical resection. Accurate staging is essential for guiding treatment and predicting outcomes. The 8th edition of the Union for International Cancer Control (UICC)/The American Joint Committee on Cancer (AJCC) TNM classification introduced depth of tumour invasion (DOI) as the criterion for T-staging (T1-T3) and a three-tiered lymph node (N) classification. This study evaluates patient stratification and prognostic accuracy of the 8th versus 7th edition in a single-centre Western cohort and discusses difficulties with measuring DOI. Patient/material and methods: Patients undergoing pancreatoduodenectomy for distal CCA at Oslo University Hospital (2015-2021) were retrospectively analysed. Tumours were restaged according to the 7th and 8th TNM editions. Survival was assessed using Kaplan-Meier estimates and log-rank tests to compare prognostic accuracy. RESULTS: Seventy-one patients were included. Using the 7th edition, most cancers (94.4%, 67 patients) were categorised as T3. With the 8th edition, stage redistribution was notable: T2 included 45 patients (63.4%) and T3 included 22 (31.0%). Five-year survival was significantly better for T2 (31.8%) than T3 (10.5%) according to the 8th edition, demonstrating improved discrimination. The revised N classification provided better prognostic distinction, with median survival of 30 months for N1 (1-3 nodes) and 23 months for N2 (≥4 nodes). INTERPRETATION: The 8th edition provides more accurate prognostic stratification of distal CCA compared to the 7th edition but requires meticulous, standardised pathology assessment to ensure accurate prognosis and appropriate post-surgical management.