Background <p>Circulating cell-free DNA (cfDNA) is a promising liquid biopsy biomarker in pancreatic ductal adenocarcinoma (PDAC), but clinical sensitivity remains limited, particularly in localized disease. Experimental studies suggest that transient modulation of hepatic clearance may increase recoverable cfDNA. Perflubutane microbubbles (Sonazoid^®), a clinically approved ultrasound contrast agent, are selectively taken up by Kupffer cells and may influence short-term cfDNA kinetics. This first-in-human pilot study primarily aimed to assess the feasibility and safety of serial cfDNA sampling and quantification following Sonazoid^® administration in patients with resectable or borderline-resectable PDAC.</p> Methods <p>This single-center prospective pilot study enrolled patients with resectable or borderline-resectable PDAC scheduled for curative-intent surgery. Perflubutane microbubbles (Sonazoid^®) were administered intravenously at the standard diagnostic dose (0.015 mL/kg). Blood samples were collected at baseline and at 5, 15, 30, and 60&#xa0;min after administration. Plasma cfDNA was extracted using a standardized protocol and quantified in duplicate by fluorometric analysis. The primary objective was feasibility, defined as successful completion of serial blood sampling, plasma processing, cfDNA extraction, and quantitative cfDNA measurement, as well as procedural safety. Changes in cfDNA concentration were assessed descriptively as an exploratory outcome.</p> Results <p>Five patients were enrolled, and all completed the full protocol without deviations. Of these, four had resectable disease and one had borderline-resectable disease. Clinical stage at presentation ranged from IB to IIIA. Serial blood collection, plasma processing, cfDNA extraction, and fluorometric quantification were successfully performed for all 25 planned samples. Baseline cfDNA concentrations ranged from 0.564 to 0.946 ng/µL. Four patients showed a decrease in cfDNA concentration at 5&#xa0;min followed by relative stability through 60&#xa0;min, whereas one patient demonstrated a transient greater-than-two-fold increase at 5&#xa0;min, followed by persistently higher-than-baseline values through 60&#xa0;min. At the cohort level, no consistent increase in cfDNA concentration was observed. No adverse events related to Sonazoid^® administration were observed.</p> Conclusions <p>Serial peri-procedural cfDNA measurement using standardized sampling and fluorometric quantification was feasible and safe in patients with resectable or borderline-resectable PDAC. Administration of perflubutane microbubbles at standard diagnostic doses did not induce a uniform or sustained increase in circulating cfDNA concentrations in this pilot cohort. These findings provide feasibility data and may inform the design of future studies evaluating cfDNA dynamics after clearance-modulating interventions in PDAC.</p> <p><i>Trial Registration</i> This study is registered in the Japan Registry of Clinical Trials (jRCT) under the identifier jRCTs071240095, registered on January 10, 2025. Registration details are available at: <a href="https://jrct.mhlw.go.jp/latest-detail/jRCTs071240095">https://jrct.mhlw.go.jp/latest-detail/jRCTs071240095</a></p>