Low CA19-9 levels may signal poor pancreatic cancer prognosis: Study

Taipei, Aug. 17 (CNA) An extremely low level of carbohydrate antigen 19-9 (CA19-9) -- a blood-based tumor marker long considered an indicator of lower pancreatic cancer risk -- may actually signal a poor prognosis, according to a multicenter study led by Taiwan's National Health Research Institutes (NHRI).

The study, which was showcased at a press conference on Monday, found that patients with CA19-9 levels of 7 units per milliliter (U/mL) or lower had a median overall survival time of just 13.5 months, comparable to patients with CA19-9 levels above 200 U/mL, a group traditionally considered high-risk that had a median survival of 12.8 months.

NHRI Vice President Sheu Huey-herng (許惠恒) said that pancreatic cancer remains one of the deadliest cancers, with about 80 percent of patients diagnosed late with a five-year survival rate of only 13.7 percent.

CA19-9 is widely used as a blood-based tumor marker for pancreatic cancer. While levels below 37 U/mL have generally been regarded as normal and higher levels linked to poorer survival outcomes, the new study found a U-shaped relationship between CA19-9 levels and survival, with both extremely low and extremely high values associated with worse prognoses.

The study, conducted with National Cheng Kung University Hospital and Kaohsiung Medical University Hospital, analyzed data from 615 pancreatic cancer patients treated from 2013-2023.

Patients with CA19-9 levels below 7 U/mL -- a group that includes people genetically unable to secrete the marker -- had a median survival time of 13.5 months. Those with levels between 7 and 37 U/mL survived a median of 23.2 months, while patients with levels between 37 and 200 U/mL survived 22 months.

NHRI assistant research fellow and physician Su Yung-yeh (蘇勇曄) said pancreatic cancer is difficult to detect early because symptoms rarely appear until the disease has advanced, leaving most patients ineligible for curative surgery.

He said the research team developed a dual-threshold CA19-9 model with an accuracy of about 88 percent that uses routine blood test results to identify previously overlooked high-risk patients without requiring genotyping.

About 10 percent of patients are genetically unable to produce CA19-9, meaning the marker may underestimate their disease risk, Su said.

He urged physicians not to regard CA19-9 levels below 7 U/mL as reassuring and instead to combine the test with other tumor markers, such as carcinoembryonic antigen (CEA), and imaging studies while maintaining close follow-up.

CA19-9 is not a stand-alone diagnostic test for pancreatic cancer and can also be elevated by other cancers or non-cancerous conditions, including inflammation and digestive diseases.

Physicians generally interpret the marker together with imaging findings and other clinical assessments rather than using it alone for cancer screening.

NHRI Cancer Research Institute Director Cha Tai-lung (查岱龍) said CA19-9 is only one factor considered in clinical decision-making, but the findings provide an important basis for future studies on whether patients with extremely low CA19-9 levels could benefit from different treatment strategies or more tailored follow-ups.

The study was published online in May in Clinical Cancer Research, a journal of the American Association for Cancer Research.