Prediction of survival after pancreatoduodenectomy for distal cholangiocarcinoma: independent external validation of a prognostic model for 3-year overall survival in Sweden

The only treatment with curative potential for distal cholangiocarcinoma (dCCA) is radical surgery which can be complemented with adjuvant chemotherapy. The aim of the present study was to perform an independent external validation of a prognostic model for 3-year overall survival based on routine clinicopathological variables for patients treated with pancreatoduodenectomy for dCCA. All patients with a histopathological confirmed dCCA that underwent pancreatoduodenectomy in Sweden from 2009 through 2019 were identified in the Swedish National Registry for Pancreatic and Periampullary Cancer. Model performance was estimated using the C-index and calibration plots. In total 220 patients were included in the study. The median survival was 33 months (IQR 26–40) and 3-year survival rate 47% (95% CI 40–53%). The prognostic model had a C-index of 0.69 (95% CI 0.62–0.72). Calibration plots revealed overestimated risk of death across risk groups in the full cohort. Calibration was good in the subgroup of patients that did not receive adjuvant treatment. The prognostic model showed reasonable discriminative ability but some miscalibration likely since the effect of adjuvant treatment is not included in the model. Given that the model was developed in cohorts treated prior to the current adjuvant standard of care the model can be used to estimate baseline risk prior to risk/benefit decision for adjuvant treatment as well as stratification for clinical trials but with a risk to underestimate 3-year overall survival for patients that receive adjuvant treatment.