Results from the first randomized controlled trial of a multi-cancer early detection (MCED) test suggest that yearly screening of a blood sample may be able to change when cancer is found.

Although the NHS-Galleri trial did not reach its primary endpoint (reducing the number of cancers found at a late stage) the results show that 3 years of Galleri screening cut the number of cancers found at stage IV.

The Galleri group also had fewer cancers found clinically because of symptoms and in emergency settings, which tend to be more advanced and harder to treat than those found by screening.

The research was presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting, which took place May 29 to June 2 in Chicago. 

“This is the first randomized controlled trial of a multi-cancer early detection test to report results, and it represents a landmark achievement for participants and the UK’s National Health Service.

The trial demonstrates that annual multi-cancer early detection testing is feasible at scale within a national health system and can increase the number of cancers detected through screening, including many for which no organized program currently exists,” said lead study author Charles Swanton, MD, PhD, The Francis Crick Institute and University College London Cancer Institute, London, United Kingdom.

The Galleri test analyzes DNA fragments circulating in the blood, called cell-free DNA (cfDNA), looking for patterns of DNA alterations that indicate the presence of cancerous cells.

The NHS-Galleri trial aimed to see if 3 years of Galleri testing, when added to standard-of-care screening, could shift the stage at which  a set of 12 prespecified cancers is found, reducing the number of cancers diagnosed at stages III and IV and increasing the number diagnosed at stages I and II.

The trial included 142,942 people in the United Kingdom who did not have symptoms of cancer. Their ages ranged from 50 to 77 years, and half were female. About 93% identified their race as White, 3% as Asian, and about 1% each as Black, mixed, or other. About 23% were ranked in the most socioeconomically disadvantaged group, and about 16% were in the least disadvantaged group.  

Every participant had blood drawn once per year for 3 years and received the recommended cancer screening tests. The participants were randomized into 2 groups:  

• Half were in the Galleri group. Their blood samples were tested using the Galleri test.  
• Half were in the control group, and their blood was not tested with the Galleri test.  

Participants who had a positive result from Galleri testing followed up with a doctor for diagnostic workup, as did participants in either group who developed symptoms related to cancer.  

Key findings

Across all cancer types, 3,637 cancers were diagnosed in the Galleri group, and 3,400 were diagnosed in the control group. In the Galleri group, 4 times more cancers were found by screening than in the group that got only the recommended screening: 1,173 cases vs. 290 cases.  

The reduction of stage III or IV diagnoses among the 12 pre-specified cancers was not significant. However, there was a shift in diagnoses of these cancers over the testing period in the Galleri group compared to the control group:

• 14% fewer at stage IV  
• 19% more at stage I, II, or III  
• It’s important to note when interpreting these data that the 12 pre-specified cancers did not include breast or cervical cancer, for which there are regular screening tests that can catch cancer at early stages. 
• It is unknown whether all the cancers found with this test would ever become symptomatic, or if early diagnosis with the Galleri test actually improves survival. 
• In addition, across all cancer types, 21% fewer were found clinically (not by screening) and 20% fewer were found as emergency presentation in the Galleri group than the control group.  
• Specificity of the Galleri test was 99.55%, and positive predictive value was 52%. Sensitivity and negative predictive value were not reported. 
• The test predicts where the cancer originated. The site-of-origin prediction was accurate in 87% of participants with cancer when the test reported 1 site, and in 92.5% when it reported the top 2 probable sites.

No participants had serious adverse events from the blood draw, although some had minor issues, such as bruising. Other impacts included short-term anxiety about a positive test result and the burden of follow-up testing.  

"While the Galleri-NHS study results show some encouraging trends toward tumour downstaging, it is important to recognize that the trial did not statistically reduce late-stage cancers by its predefined primary endpoint.

Nevertheless, these findings still offer genuine hope for deadly malignancies that currently lack screening options, such as ovarian and pancreatic cancer.

Longer-term follow-up and the eagerly awaited results of the US REACH trial will provide the critical additional information we need to fully evaluate the population-level benefits versus the risks of MCEDs,” said Julie R. Gralow, MD, FACP, FASCO, ASCO Chief Medical Officer and Executive Vice President. 

The trial will continue with additional time for follow-up to see if the reduction in stage IV diagnoses  further  improves  over  time  and  if Galleri testing extends lifespan. 

Studies will also be done to weigh the costs and benefits of regular MCED testing for cancer detection. 

Source: ASCO