Risk factors for latent distant organ metastasis detected by staging laparoscopy in patients with radiologically defined locally advanced pancreatic ductal adenocarcinoma

Objectives We aimed to identify risk factors for latent distant organ metastasis in patients with radiographically defined locally advanced (RDLA) pancreatic ductal adenocarcinoma (PDAC). Methods RDLA disease was defined as unresectable disease without distant organ metastasis based on resectability status by NCCN guidelines. Between January 2005 and November 2015, 110 consecutive patients underwent staging laparoscopy to rule out latent distant metastasis. Univariate and multivariate analyses were performed to identify risk factors for latent distant organ metastasis or peritoneal metastasis (PM), defined as peritoneal dissemination and/or positive peritoneal lavage cytology (PPC). Results Latent distant organ metastasis was diagnosed by staging laparoscopy in 62 patients. PPC was found in 23%, peritoneal dissemination in 19%, and liver metastasis in 15%. Univariate analysis showed tumor location, preoperative CA 19-9 level and tumor size, and multivariate analysis revealed tumor size > 55 mm and CA 19-9 level > 60 IU/ml as risk factors for latent distant metastasis. Multivariate analysis showed pancreas body-tail tumors and tumor size > 42 mm as risk factors for PM; 65.4% of pancreas body-tail tumors > 42 mm had PM. Conclusions Patients with large pancreas body-tail tumors and high CA 19-9 level are at greater risk for latent distant organ metastasis or PM, and should undergo staging laparoscopy routinely for accurate diagnosis (UMIN000023125).