Development of a Prognostic Scoring System To Select Candidates for Irradiation Stent Implantation for Patients with Unresectable Biliary Tract Cancer

Background: Compared with conventional metal stent, irradiation stent can prolong the stent patency and the survival time of patients. We aimed to develop a predictive model to select appropriate candidates for irradiation stent implantation among patients with biliary obstruction caused by unresectable biliary tract cancer (BTC). Methods: The training cohort consisted of 130 patients from three centers, and an external independent center was allocated as the validation cohort with 43 patients. We constructed a prognostic nomogram and risk classification system to select appropriate patients with unresectable BTC for irradiation stent implantation. Findings: The C-index of the nomogram was 0·724 and 0·736 in the training cohort and validation cohort, respectively. The calibration curves showed good consistency of survival between the actual observation and nomogram prediction in both cohorts. A risk classification system was built to stratify patients into three risk strata. In the training cohort, the median survival of patients in the low-, intermediate-, and high-risk groups were 10·1 months (95% CI 9·1–11·1), 4·6 months (95% CI 3·6–5·6), and 1·5 months (95% CI 0·1–3·0), respectively. Interpretation: According to this newly developed predictive model, irradiation stents are highly recommended for patients in the low-risk group (score≤100) for long-term survival benefit but not recommended for those in the high-risk group (score≥166·5). Funding: This study was supported by the National Key Research and Development Project of China (2018YFA0704100), the National Natural Science Foundation of China (Major Scientific Research Instrument Development Program 81827805, 81441054, 81671796), Jiangsu Provincial Medical Youth Talent Program (ZDRCA2016078), the Key Research and Development Project of Jiangsu Province (BE2019750) and Innovation Platform of Jiangsu Provincial Medical Center (YXZXA2016005). Declaration of Interest: The authors have no conflicts of interest to declare. Ethical Approval: This multicenter retrospective study was approved by the institutional review boards at all participating centers. The requirement for written informed consent was waived due to the retrospective nature of the study.