Nodal CTV selection according to primary tumour location and pT stage for biliary tract cancer

To assist radiation oncologists in determining the elective nodal CTV for biliary tract cancer, we aimed to provide the rules for selection of the CTV for each subsite of biliary tract with respect to the pT stage, based on the analysis of the incidence and location of metastatic lymph nodes.

Systematic review and meta-analysis was performed to determine the rate of pathological nodal involvement of each individual lymph node station (LNS) as a function of the primary tumour pT stage (pT1-2 vs. pT3-4) separately for right intrahepatic cholangiocarcinoma (rIHC), left/hilar intrahepatic cholangiocarcinoma l/hIHC), proximal extrahepatic cholangiocarcinoma (pEHC), middle extrahepatic cholangiocarcinoma (mEHC), distal extrahepatic cholangiocarcinoma (dEHC) and gall bladder cancer (GBC). A 5% or higher risk of involvement was assumed to justify inclusion of the LNS in the CTV.

Coeliac LNS, which is usually included in the CTV in clinical practice, has a low risk of involvement and can presumably be omitted for pT1-2 GBC, for dEHC irrespective of pT stage and for mEHC. Para-aortic and superior mesenteric artery (SMA) LNS that are usually omitted have a high risk of involvement. Para-aortic LNS should be considered for inclusion for all the subsites except for pT1-2 dEHC, and SMA LNS for all the subsites except for pT1-2 dEHC, pT1-2 GBC and pEHC. Left gastric artery, lesser curvature and paracardial LNS should be considered for inclusion for l/hIHC.

This systematic review provides an evidence-based strategy for nodal CTV selection in biliary tract cancer according to primary tumour location and pT stage.