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

## TL;DR

The apoA2-i index is a new tumor marker that can detect pancreatic cancer, especially in cases where another marker, CA19-9, is negative.

## Contribution

The apoA2-i index is introduced as a novel tumor marker for pancreatic cancer with potential clinical utility.

## Key findings

- The apoA2-i index detected 65.8% of pancreatic cancer cases with 85.7% specificity.
- Combining apoA2-i index with CA19-9 improved sensitivity to 78.9%.
- The apoA2-i index detected 52.9% of CA19-9-negative pancreatic cancer cases.

## Abstract

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.