# CA 19-9

Source: https://onco.cc/terms/ca19-9/  
OnCo record `ca19-9` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

A sugar molecule shed into the blood by most pancreatic cancers; useful to follow treatment, not to screen.

## Summary

Sialyl-Lewis A carbohydrate antigen elevated in ~80% of PDAC; 5-10% of people (Lewis-negative) cannot make it. Prognostic at diagnosis, tracks response and recurrence, and defines eligibility in trials. Too non-specific for population screening (raised in biliary obstruction, pancreatitis), but glycan-engineered variants and combination with cfDNA are under study for high-risk surveillance.

## Fields

- Kind: Term
- Last checked: 2026-09-06

## Notes

- In symptomatic patients CA 19-9 is 79 to 81 percent sensitive and 82 to 90 percent specific; as a screening test its positive predictive value is 0.5 to 0.9 percent; a level above 100 U/mL suggests unresectable or metastatic disease, and a fall of 20 to 50 percent or normalisation after surgery or chemotherapy predicts longer survival (Ballehaninna 2012).
- A CA 19-9 above 500 U/mL makes an anatomically resectable tumour biologically borderline resectable in the 2017 international consensus (Isaji 2018). Not every Lewis-negative patient is a non-secretor: 27.4 percent of Lewis-negative patients in a 1,482-patient series still had a raised level (Luo 2018).
- Pancreatic ductal adenocarcinoma: pooled sensitivity 79% and specificity 82% across 2,283 patients, with cholestasis raising it falsely (Goonetilleke 2007). Baseline level is prognostic (5.8 against 10.3 months above the median) but a 50% fall on chemotherapy is not a valid surrogate for survival once guarantee-time bias is corrected (Hess 2008). About 10% of patients are Lewis-negative (FUT3-null) and cannot make it at all, with median 2.4 against 496 U/mL and survival as poor as the highest-marker group; 7 U/mL or below identifies them with 95% positive predictive value (Tempero 1987, Yeh 2026). Levels rise about two years before diagnosis, reaching 60% sensitivity only in the last six months (Fahrmann 2021).

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/CA19-9
- Wikipedia: https://en.wikipedia.org/wiki/CA19-9
- Ballehaninna and Chamberlain, J Gastrointest Oncol 2012: clinical utility of serum CA 19-9 in pancreatic adenocarcinoma: https://doi.org/10.3978/j.issn.2078-6891.2011.021
- Luo, Pancreatology 2018: CA19-9 in Lewis-negative patients with pancreatic cancer (1,482 patients): https://doi.org/10.1016/j.pan.2018.08.003
- Isaji, Pancreatology 2018: international consensus on the definition and criteria of borderline resectable pancreatic cancer: https://doi.org/10.1016/j.pan.2017.11.011

## Connected records

- cancers: [Ampullary cancer (ampulla of Vater)](https://onco.cc/cancers/ampullary/), [Biliary tract cancer (cholangiocarcinoma)](https://onco.cc/cancers/cholangiocarcinoma/), [Borderline resectable pancreatic ductal adenocarcinoma](https://onco.cc/cancers/borderline-resectable-pdac/), [Extrahepatic cholangiocarcinoma (perihilar and distal)](https://onco.cc/cancers/extrahepatic-cholangiocarcinoma/), [Gallbladder cancer](https://onco.cc/cancers/gallbladder/), [Intraductal papillary mucinous neoplasm and other pancreatic cystic precursors](https://onco.cc/cancers/ipmn-cystic-precursors/), [KRAS G12C-mutant pancreatic ductal adenocarcinoma](https://onco.cc/cancers/kras-g12c-pdac/), [Locally advanced unresectable pancreatic ductal adenocarcinoma](https://onco.cc/cancers/locally-advanced-pdac/), [Metastatic pancreatic ductal adenocarcinoma](https://onco.cc/cancers/metastatic-pdac/), [Pancreatic ductal adenocarcinoma](https://onco.cc/cancers/pancreatic/), [Resectable pancreatic ductal adenocarcinoma](https://onco.cc/cancers/resectable-pdac/)
- technologies: [High-risk pancreatic surveillance (CAPS / PRECEDE)](https://onco.cc/technologies/pancreatic-surveillance/), [Serum tumour markers: proper use and misuse](https://onco.cc/technologies/serum-tumour-markers/)
- terms: [High-risk stigmata and worrisome features of pancreatic cysts (IPMN and MCN surgical criteria)](https://onco.cc/terms/pancreatic-cyst-high-risk-stigmata/), [Lewis-negative (Lewis antigen-negative, CA 19-9 non-secretor) status](https://onco.cc/terms/lewis-negative/), [New-onset diabetes as a signal of pancreatic cancer (and the ENDPAC score)](https://onco.cc/terms/new-onset-diabetes-pancreatic-cancer/), [Resectability classes for pancreatic cancer (NCCN anatomical criteria and the 2017 international consensus)](https://onco.cc/terms/nccn-resectability-criteria-pancreatic/)
- key papers: [A new CA19-9 cutoff value identifies Lewis antigen status and refines prognostic stratification in PDAC](https://onco.cc/key-papers/paper-yeh-ca19-9-lewis-negative-fut3-cutoff-ccr-2026/), [CA 19-9 tumour-marker response to chemotherapy in patients with advanced pancreatic cancer enrolled in a randomised controlled trial](https://onco.cc/key-papers/paper-hess-ca19-9-response-chemotherapy-lancet-oncol-2008/), [Combined circulating tumor DNA and protein biomarker-based liquid biopsy for the earlier detection of pancreatic cancers](https://onco.cc/key-papers/paper-cohen-ctdna-protein-liquid-biopsy-pancreatic-pnas-2017/), [Lead-Time Trajectory of CA19-9 as an Anchor Marker for Pancreatic Cancer Early Detection](https://onco.cc/key-papers/paper-fahrmann-ca19-9-lead-time-gastroenterology-2021/), [Pancreatic cancer early detection biomarkers for high-risk individuals: insights from the PRECEDE consortium](https://onco.cc/key-papers/paper-worthington-precede-early-detection-biomarkers-ijc-2026/), [Real-world analysis of ctDNA and other biomarkers in patients with curatively resected stage I-III biliary tract cancer](https://onco.cc/key-papers/paper-malla-ctdna-resected-biliary-tract-cancer-esmo-gi-onc-2026/), [Relationship of carbohydrate antigen 19-9 and Lewis antigens in pancreatic cancer](https://onco.cc/key-papers/paper-tempero-ca19-9-lewis-antigens-cancer-res-1987/), [Systematic review of carbohydrate antigen (CA 19-9) as a biochemical marker in the diagnosis of pancreatic cancer](https://onco.cc/key-papers/paper-goonetilleke-ca19-9-systematic-review-ejso-2007/)
- ideas: [Blood-based pancreatic cancer detection in new-onset diabetes](https://onco.cc/ideas/idea-mced-new-onset-diabetes/), [Run the ENDPAC score on every new diabetes diagnosis after 50 and scan the high scorers](https://onco.cc/ideas/idea-pdac-new-onset-diabetes-risk-score-pathway/)
- roadmaps: [Pancreatic cancer roadmap: from Whipple's operation to gemcitabine, FOLFIRINOX, adjuvant chemotherapy, PARP inhibition, KRAS inhibition, vaccines and the surveillance question](https://onco.cc/roadmaps/pancreatic-roadmap/)
- trials: [MPACT](https://onco.cc/trials/mpact/), [PANFIRE-2](https://onco.cc/trials/panfire-2/), [SCALOP](https://onco.cc/trials/scalop/)
- bottlenecks: [The hardest cancers are found late](https://onco.cc/bottlenecks/b-early-detection/)

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