A multicancer early-detection blood test did not lower stage III or IV cancer incidence after three screening rounds

Design

Randomised controlled trial in England, blood tested vs stored, up to three annual rounds (manufacturer-funded)

Population

142,250 people aged 50 to 77 (71,122 intervention, 71,128 control)

Primary outcome

Incidence rate of stage III or IV cancer among 12 prespecified cancer types

Effect

Incidence rate ratio 1.03 (95% CI 0.92 to 1.14; P = 0.63); stage IV ratio 0.86 (0.74 to 1.00)

NHS-Galleri was a randomised, controlled trial in England of a blood-based multicancer early-detection test added to usual care. People aged 50 to 77 gave blood at up to three annual visits. After baseline blood collection, 71,122 were assigned to have their blood tested and 71,128 to have it stored. Participants and trial staff were initially unaware of the group.

The primary end point was the incidence rate of stage III or IV cancer among 12 prespecified cancer types. It did not differ between groups (incidence rate ratio 1.03, 95% CI 0.92 to 1.14; P = 0.63). The key secondary end point, stage IV cancer, had a ratio of 0.86 (95% CI 0.74 to 1.00) after three rounds. Fewer than 1% of participants had trial-related adverse events, and none were serious. The trial was funded by the test manufacturer.

The result does not show benefit on the primary outcome. The stage IV signal has an interval that touches 1.00 and was not the primary end point, and the authors say further follow-up is warranted to see how both comparisons evolve. The trial did not report cancer mortality in this abstract, so it cannot show whether the test saves lives.

• Do not offer a multicancer blood test as a replacement for organised screening on the strength of this trial.
• The incidence of stage III or IV cancer was not lower with testing (rate ratio 1.03).
• The stage IV ratio of 0.86 was a secondary result with an interval reaching 1.00.
• Patients may ask about commercial tests; explain that benefit on the main outcome was not shown.

Why it matters

It is a large randomised test of whether finding cancers earlier with a blood test shifts the stage at which cancers are diagnosed.

Don't overread it

The primary outcome was neutral, the stage IV result is secondary, and mortality was not reported, so the trial cannot say whether the test saves lives.

The statistics, in plain English

An incidence rate ratio of 1.03 with an interval of 0.92 to 1.14 means the test group had about the same rate of late-stage cancer as the control group. The secondary result sits right at the edge of significance and, as a secondary comparison, should be treated as a lead for follow-up and not as a finding.

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