# CCGA: the Circulating Cell-free Genome Atlas behind the Galleri methylation test

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

## TL;DR

CCGA is the case-control programme of about 15,000 people that trained and validated the Galleri blood test, which reads methylation patterns on cell-free DNA to say whether a cancer signal is present and where it comes from. Its third sub-study set the figures still quoted: very few false positives, but only about one in six stage I cancers detected.

## Summary

The Circulating Cell-free Genome Atlas enrolled participants with and without cancer across more than 50 cancer types and used their plasma to develop a targeted methylation classifier; the third sub-study, in 4,077 participants (2,823 with cancer, 1,254 without), was the clinical validation of the refined test. Specificity was 99.5%; sensitivity across all cancers rose with stage, 16.8% at stage I, 40.4% at stage II, 77.0% at stage III and 90.1% at stage IV, and the predicted cancer signal origin was correct in 88.7% of true positives (Klein 2021). Pancreatic cancer was one of the twelve pre-specified cancers that account for most cancer deaths, and its per-cancer sensitivity in the study is higher than the all-cancer average at each stage, which is why pancreatic cancer features in the case for multi-cancer screening; the stage I figure is the honest limit. The test is sold as Galleri and is on the record's pipeline; the record's open problems note that its sensitivity for stage I disease is low and its positive predictive value in average-risk adults poor. DETECT-A tested the predecessor approach prospectively.

## Fields

- Kind: Term
- Last checked: 2026-09-24
- Also known as: CCGA; CCGA3; Circulating Cell-free Genome Atlas; Galleri validation study
- Tags: pancreatic-molecular

## Sources

- Klein et al., Ann Oncol 2021: CCGA3 validation of the Galleri methylation test in 4,077 participants: https://doi.org/10.1016/j.annonc.2021.05.806

## Connected records

- cancers: [Pancreatic ductal adenocarcinoma](https://onco.cc/cancers/pancreatic/)
- technologies: [Cell-free DNA methylation tests](https://onco.cc/technologies/cfdna-methylation-testing/), [DNA methylation profiling](https://onco.cc/technologies/methylation-profiling/), [Multi-cancer early detection (MCED)](https://onco.cc/technologies/mced/)
- drugs: [Galleri](https://onco.cc/drugs/galleri/)
- terms: [Cell-free DNA (cfDNA)](https://onco.cc/terms/cfdna/), [DETECT-A: a blood test plus PET-CT to screen 10,006 women with no symptoms](https://onco.cc/terms/detect-a-study/), [Positive predictive value (PPV)](https://onco.cc/terms/ppv/), [Stage shift](https://onco.cc/terms/stage-shift/)
- key papers: [Clinical validation of a targeted methylation-based multi-cancer early detection test using an independent validation set](https://onco.cc/key-papers/paper-klein-ccga3-mced-validation-ann-oncol-2021/)

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