Clinical Target Volume in Biliary Carcinoma: A Systematic Review of Pathological Studies

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Abstract
Background/Aim: Radiotherapy is a treatment option for both adjuvant and neo-adjuvant settings for biliary tract cancer. Guidelines on the delineation of the target volume of lymph nodes are lacking; only generic indications are available, without specific recommendations for different primary tumour locations (e.g. intrahepatic, extrahepatic biliary tract or gallbladder cancer). The aim of this study was to systematically review available literature to provide recommendations on lymph node target volume delineation in patients with unresectable biliary tumour. Materials and Methods: A systematic search of electronic databases was performed up to July 2016. The primary outcome measure was the rate of lymph node involvement according to the location of primary biliary tumour. Sites with ≥5% of nodal metastases were considered in the clinical target volume for radiotherapy planning. Results: Twelve studies (1075 patients) were included. The most frequent site of lymph node metastasis in intrahepatic biliary tree carcinoma was retroportal (61.1%, 95% confidence interval (CI)=50.7-70-6%). Other frequently involved lymph nodes were along the hepatoduodenal ligament [frequency=38.7%, 95% CI=31.0-47.0%], those along the common hepatic artery (17.0%, 95% CI=8.2-31.9%) and the hilar nodes (16.9%, 95% CI=13.2-21.4%). In extrahepatic biliary tree cancer, the most frequently involved lymph nodes were the pericholedochal (42.7%, 95% CI=33.8-52.1%) and those along the hepatoduodenal ligament (40.3%, 95% CI=32.4-48.8%). Other commonly involved nodal regions included retroportal lymph nodes (30.9%, 95% CI=23.0-40.1%), pancreaticoduodenal anterior and posterior nodes (30.1%, 95% CI=12.2-57.1%), those along the common hepatic artery (19.7%, 95% CI=11.8-31.0%) and para_aortic nodes (15.2%, 95% CI=8.0-27.0%). The most common site of metastases in gallbladder cancer were the pericholedochal nodes (25.2%, 95% CI=18.6-33.2%), those along the cystic duct (23%, 95% CI=16.6-30.8%), and retroportal nodes (17.1%, 95% CI=11.6-24.5%). Conclusion: Biliary tract cancer has a high propensity for regional lymphatic metastases. An evidence-based nodal target definition of biliary tract cancer based on primary tumour location was proposed.

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