Clinical Utility of the Apolipoprotein A2 Isoform Index as a Tumor Marker for Pancreatic Cancer

We investigated the clinical utility of the apolipoprotein A2 isoform index (apoA2-i index), a novel tumor marker for pancreatic cancer, in clinical practice, particularly for CA19-9-negative pancreatic cancer.

Between May 2024 and July 2025, patients who underwent abdominal computed tomography (CT) for the differential diagnosis of pancreatic diseases had their CEA, CA19-9, and apoA2-i indexes measured. We evaluated the sensitivity and specificity for pancreatic cancer and analyzed the relationship between the apoA2-i index and pancreatic atrophy or main pancreatic duct dilatation on CT.

A total of 115 patients were included: 38 with pancreatic cancer, 47 with intraductal papillary mucinous neoplasms (IPMNs), and 30 with other conditions. The median age was 72.0 years, and 55 patients (47.8%) were male. The sensitivity of apoA2-i index for pancreatic cancer was 65.8%, while the specificity was 85.7%. The combined use of CA19-9 and the apoA2-i index increased sensitivity to 78.9% (specificity, 81.8%). Among 17 patients with CA19-9-negative pancreatic cancer, 9 (52.9%) tested positive for the apoA2-i index. The positive rates for stage 0/I pancreatic cancer were 12.5% for CA19-9 and 62.5% for the apoA2-i index. Regarding CT findings, the apoA2-i index significantly decreased with the progression of pancreatic atrophy (p = 0.027) and was also significantly lower in patients with pancreatic duct dilatation (p = 0.016).

The apoA2-i index can detect CA19-9-negative pancreatic cancer, and the combination of the apoA2-i index with CA19-9 enhances diagnostic performance in clinical practice.