Regional lymphadenectomy vs. extended lymphadenectomy for hilar cholangiocarcinoma (Relay-HC trial): study protocol for a prospective, multicenter, randomized controlled trial.

<bold>Background: </bold>The prognostic benefits and safety of extended lymphadenectomy for hilar cholangiocarcinoma remain uncertain. The available evidence is still insufficient concerning its retrospective aspect. The aim of this study is to explore the clinical effect and safety of extended lymphadenectomy compared to regional lymphadenectomy in patients with hilar cholangiocarcinoma.<bold>Methods: </bold>The Relay-HC trial is a prospective, multicenter, and randomized controlled trial. Seven hundred and thirty-four eligible patients with resectable perihilar cholangiocarcinoma across 15 tertiary hospitals in China will be randomly assigned (1:1) to receive either regional lymphadenectomy or extended lymphadenectomy. The primary objective is to determine the overall survival after the two approaches. Secondary objectives of the study include the evaluation of perioperative mortality, postoperative complication, and disease-free survival. This study has been approved by the ethics committee of each participating hospital.<bold>Discussion: </bold>The Relay-HC trial is designed to investigate the prognostic benefits and safety of expanded lymphadenectomy for hilar cholangiocarcinoma. Currently, it has never been investigated in a prospective randomized controlled clinical trial.<bold>Trial Registration: </bold>Chinese Clinical Trial Registry (ChiCTR), ChiCTR1800015688 . Registered on 15 April 2018. [ABSTRACT FROM AUTHOR]