Prognostic impact of peritoneal washing cytology in patients with biliary tract cancer

Purpose To elucidate the clinical significance of peritoneal washing cytology (PWC) in patients with resectable biliary tract cancer (BTC). Methods Clinical data of patients with BTC, who received PWC at curative intent surgery from March 2009 to December 2021, were retrospectively analyzed. Eligible patients were stratified into two groups according to positive or negative PWC. Recurrence-free survival and overall survival were compared between the two groups. Independent factors associated with positive PWC were investigated using multivariate analysis. Results Among the 284 patients analyzed, all 53 patients with ampullary carcinoma showed negative PWC and these patients were excluded. Among the remaining eligible 231 patients, 41 patients had intrahepatic cholangiocarcinoma, 55 had gall bladder carcinoma, 72 had hilar cholangiocarcinoma, and 63 had distal cholangiocarcinoma. Eleven (4.8%) patients had positive PWC, and 220 (95.2%) had negative PWC. The median recurrence-free survival in the positive and negative PWC groups were 12.0 vs. 60.7 months ( p = 0.005); the median overall survival times were 17.0 vs. 60.6 months ( p = 0.008), respectively. Multivariate analysis revealed that serum carbohydrate antigen 19–9 level over 80 U/mL and multiple lymph node metastasis were independently associated with positive PWC (odds ratio [OR]: 5.84, p = 0.031; OR: 5.28, p = 0.021, respectively). Conclusion Patients with positive PWC exhibited earlier recurrence and shorter survival times compared with those with negative PWC.