Purpose: To elucidate the effectiveness of circulating tumor DNA (ctDNA) for predicting occult metastases in patients with pancreatic cancer without apparent metastases. Methods: Circulating tumor DNA was obtained from plasma samples of 165 patients with pancreatic cancer and analyzed using droplet digital PCR. The prevalence and allele frequencies of ctDNA were compared across different patterns and degrees of metastatic spread. Results: Of the 142 patients without apparent metastases who underwent abdominal exploration, 39 (27.5%) harbored occult metastases including positive peritoneal lavage cytology. The prevalence of ctDNA was significantly higher in patients with occult metastases than in those without (41.0% vs 14.6%, P =.001). A markedly high prevalence of ctDNA was observed in patients with radiographically visible metastases (78.3%). ctDNA was found to be an independent predictor of the presence of occult metastases (odds ratio: 3.113, P =.039), and its diagnostic performance in combination with tumor markers had a sensitivity of 66.7% and a specificity of 81.6%. In 62 treatment-naïve patients without metastases, multivariate analysis identified the presence of ctDNA as an independent prognostic factor (hazard ratio: 6.311, P =.001). Conclusion: Circulating tumor DNA can help predict the presence of occult metastases in pancreatic cancer patients with radiographically non-metastatic disease.
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