Does the Galleri Blood Test Catch Cancer Earlier?

Does the Galleri blood test catch cancer earlier?

Not yet, based on the first results. In the NHS-Galleri trial of 142,250 adults in England, three yearly rounds of a multicancer blood test did not lower the rate of stage III or IV cancer diagnoses compared with usual care. There was a possible drop in stage IV cancers, but that result sat right on the edge of what could be chance.

The promise of a multicancer blood test is simple. One blood draw, checked for signals from many types of cancer at once, could find tumors before they spread. Finding cancer earlier only matters if it means fewer people end up with advanced disease. That is exactly what this trial set out to measure, and it is the right question to ask of any screening test.

What the trial did

Researchers enrolled people aged 50 to 77 in England and collected their blood at up to three yearly visits. After the first blood draw, participants were randomly split into two equal groups. In one group, the blood was tested. In the other group, the blood was stored and not tested, and those people simply got usual care. At first, neither the participants nor the trial staff knew who was in which group.

In total, 71,122 people were assigned to the tested group and 71,128 to the control group. The main goal was to count stage III or IV cancers among 12 cancer types chosen in advance. Stage III and IV are the advanced stages, when cancer has grown or spread and is harder to treat. The team also tracked stage IV cancer on its own, the most advanced stage. Results were measured after three screening rounds and at least 12 months of follow-up after the last person’s third visit.

What the data show

For the main goal, the tested group had a stage III or IV cancer rate about 3% higher than the control group (incidence rate ratio 1.03). In plain terms, that is no real difference. The true effect is very likely somewhere between 8% lower and 14% higher (95% CI 0.92 to 1.14). The p-value was 0.63, which means a gap this small would show up by chance alone most of the time.

Stage IV cancers told a slightly different story. The tested group had about 14% fewer stage IV diagnoses (incidence rate ratio 0.86). But the likely range runs from about 26% lower all the way to no difference at all (95% CI 0.74 to 1.00). That is a borderline result. It hints at a benefit without proving one.

Safety looked good. Fewer than 1% of participants had a trial-related side effect, and none were serious.

Dr. Kumar’s Take

This is the trial many people have been waiting for, and the main answer is no. Across three rounds of testing, the multicancer blood test did not reduce the number of people diagnosed with advanced cancer. That was the primary goal, and the trial did not meet it.

The stage IV signal is interesting, and I understand why it will get attention. But a secondary result with a range that touches “no effect” is a reason to keep watching, not a reason to celebrate. The authors say the same thing: further follow-up is needed to see how both the stage III or IV results and the stage IV gap change over time.

I also think it matters who paid for the study. It was funded by Grail, and several of the authors work for Grail. That does not make the results wrong. It does mean independent confirmation carries extra weight here. A blood test that finds more cancer is not automatically a blood test that saves lives. The bar for screening is fewer advanced cancers and, ultimately, fewer deaths, and this trial has not cleared the first bar yet.

Safety, limits, and caveats

The follow-up so far is short. Cancers that were caught earlier because of the test could take years to show a difference in advanced disease. The trial only counted 12 cancer types for its main goal, so it does not show how the test performs for every cancer. It was also done in England, within the NHS, so the results may not carry over to other health systems. None of this changes the headline result. It just means the story is not finished.

Practical Takeaways

A multicancer blood test did not lower advanced cancer diagnoses in this large trial, so it should not be treated as a proven way to prevent late-stage cancer.
Do not use a multicancer blood test as a replacement for screening tests with proven benefit, such as the ones your doctor recommends for your age and risk.
If you are thinking about paying for a multicancer blood test, ask your doctor what a positive or negative result would mean for you before you get it.
Watch for longer follow-up from the NHS-Galleri trial, since the authors say the stage IV results need more time to become clear.

FAQs

Is the Galleri test worth getting?

This trial does not show that it lowers your chance of being diagnosed with advanced cancer. That was the main thing it was designed to prove, and it did not. The test was safe in the trial, with fewer than 1% of people having a trial-related side effect and none serious. But safe and useful are two different things. Until longer follow-up shows a real drop in advanced cancers, it is best seen as an unproven add-on, not a core screening test.

Why would a test that finds cancer not reduce late-stage cancer?

A screening test has to do more than spot cancer. It has to find it early enough, and often enough, that treatment changes what happens next. If a test mostly finds cancers that were already advanced, or finds early cancers that would not have caused harm, the number of late-stage diagnoses may not change. That gap between “detected” and “helped” is why screening trials count advanced cancers and deaths, not just positive results.

What does the stage IV result mean?

The tested group had about 14% fewer stage IV cancers, but the plausible range stretched all the way to no difference. This was a secondary goal, not the main one, so it carries less weight. It could turn into a real benefit with more follow-up, or it could fade. The researchers themselves say more time is needed to see how it evolves.

Bottom Line

In a trial of 142,250 adults in England, three yearly rounds of a multicancer blood test did not reduce stage III or IV cancer diagnoses compared with usual care. A borderline 14% drop in stage IV cancers is worth following, but it is not proof of benefit. For now, a multicancer blood test is not a proven way to prevent advanced cancer, and proven screening should come first.

Read the full study