# A new CA19-9 cutoff value identifies Lewis antigen status and refines prognostic stratification in PDAC

Source: https://onco.cc/key-papers/paper-yeh-ca19-9-lewis-negative-fut3-cutoff-ccr-2026/  
OnCo record `paper-yeh-ca19-9-lewis-negative-fut3-cutoff-ccr-2026` (Key paper). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Genotyping 615 patients showed that about one in ten cannot make CA 19-9, that their outlook is as poor as patients with very high readings, and that a value of 7 or below is a practical way to spot them without a genetic test.

## Summary

Germline whole-exome sequencing in a multicentre cohort of 615 patients with pancreatic ductal adenocarcinoma determined FUT2 and FUT3 genotypes. Receiver operating characteristic analysis identified the optimal CA 19-9 cut-off for FUT3-null status and maximally selected rank statistics derived cut-offs stratifying overall survival in a training set (307) tested in a validation set (308). FUT3-null patients had similar demographics but a much lower median baseline CA 19-9 (2.4 against 496 U/mL) and a median overall survival of 13.5 months, comparable with FUT3-intact patients above 200 U/mL (12.9 months). A cut-off of 7 U/mL identified FUT3-null status with positive predictive value 95.1% and accuracy 87.9%. Using 7 and 200 U/mL without genotyping gave four prognostic groups: above 7 to 37 (23.2 months), above 37 to 200 (22 months), above 200 (12.8 months) and 7 or below, likely FUT3-null (13.5 months).

## Fields

- Kind: Key paper
- Last checked: 2026-09-24
- Journal: Clinical Cancer Research
- Year: 2026
- DOI: 10.1158/1078-0432.ccr-25-4564
- Authors: Yeh CM, Yu CC, Lee AF, et al.
- Findings: About 10% of patients are FUT3-null non-producers with median CA 19-9 2.4 against 496 U/mL.; CA 19-9 of 7 U/mL or below identifies them with 95.1% positive predictive value.; Non-producers have the same poor survival as patients above 200 U/mL.
- What it means: A very low CA 19-9 is not reassurance: it marks the non-producer group whose outlook matches the highest-marker group, and it gives clinics a rule they can apply without genotyping.
- Caveats: Taiwanese multicentre cohort; the 10% non-producer share varies by ancestry.; Retrospective derivation and validation within one cohort.

## Sources

- Yeh et al., Clin Cancer Res 2026: FUT3-null (Lewis-negative) patients and a CA 19-9 cut-off in 615 patients: https://doi.org/10.1158/1078-0432.ccr-25-4564
- PubMed: https://pubmed.ncbi.nlm.nih.gov/42162970/

## Connected records

- cancers: [Pancreatic ductal adenocarcinoma](https://onco.cc/cancers/pancreatic/)
- technologies: [Germline (hereditary) testing](https://onco.cc/technologies/germline-testing/)
- terms: [CA 19-9](https://onco.cc/terms/ca19-9/), [Founder mutation (BRCA1 185delAG and 5382insC, BRCA2 6174delT)](https://onco.cc/terms/founder-mutation/)
- journals: [Clinical Cancer Research](https://onco.cc/journals/clinical-cancer-research/)

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