Postoperative recurrent patterns of gallbladder cancer: possible implications for adjuvant therapy.

<bold>Background: </bold>Gallbladder cancer (GBC) is an uncommon malignancy with high recurrent rate and poor prognosis. This study investigates the recurrent patterns of postoperative GBC, with the aim to guide the adjuvant treatments, including the radiotherapy.<bold>Methods: </bold>Retrospectively analyzed the 109 GBC patients who underwent surgery in our institution from January 2013 to 2018. Clinical follow-up revealed 54 recurrent cases, of which 40 had detailed locations of recurrence. The sites of recurrence were recorded and divided into the tumor bed, corresponding lymphatic drainage area, intrahepatic recurrence, and the other distant metastasis.<bold>Results: </bold>The median follow-up time is 34 months (IQR: 11-64). The median disease-free survival (DFS) and overall survival (OS) were 48.8 months and 53.7 months, respectively. Through univariate analysis, risk factors for DFS and OS include tumor markers (CA199 and CEA), hepatic invasion, perineural invasion, lymphovascular invasion, TNM staging and tumor differentiation. Through multivariate analysis, risk factors for DFS include hepatic invasion and TNM staging, and for OS is TNM staging only. Of the 40 cases with specific recurrent sites, 29 patients (29/40, 72.5%) had recurrence in the potential target volume of postoperative radiotherapy (PORT), which include tumor bed and corresponding lymphatic drainage area. The common recurrent lymph node groups included abdominal para-aortic lymph node (No.16, 15/29), hepatoduodenal ligament lymph node (No.12, 8/29), retro-pancreatic head lymph node (No.13, 7/29) and celiac axis lymph node (No.9, 4/29). Twenty cases with recurrences inside the potential PORT target volume were accompanied by distant metastasis. Another 11 cases had distant metastasis alone, so totally 31 cases developed distant metastasis (31/40, 77.5%), including 18 cases with hepatic metastasis.<bold>Conclusion: </bold>The recurrence and metastasis rates are high in GBC and adjuvant therapy is needed. Up to 75% of the recurrent cases occurred in the potential target volume of postoperative radiotherapy, suggesting that postoperative radiotherapy has the possible value of improving local-regional control. The potential target volume of radiotherapy should include the tumor bed, No.8, No.9, No.11, No.12, No.13, No.14, No. 16a2, No. 16b1 lymph node groups. [ABSTRACT FROM AUTHOR]