Did the test help find cancer early?

Key points

• Cancers can be found at different stages. People whose cancers are found at an earlier stage usually have more treatment options. 
• There was no difference in the number of late-stage cancers overall (stage 3 and stage 4 cancers together) in people who had the test and those who did not. This means that the trial did not meet its main goal. 
• There were fewer of the most advanced cancers (stage 4) in people who had the test. 
• There were more early stage cancers (stage 1 and 2) in people who had the test. 

The aim of the NHS-Galleri trial was to see if using the Galleri® blood test could help the NHS find cancer early. Finding cancer early usually means people have more treatment options and better outcomes.

This was measured by looking at the stage at which cancers were diagnosed in people taking part in the trial.

Cancer stage describes how big a cancer is and if it has spread. It helps doctors understand if a cancer is early in its development or more advanced. Stage 1 is the earliest stage, and stage 4 is the most advanced. 

Not all cancers are given a stage or are staged in the same way. However, using this system gives a general idea of how serious a cancer is.

The benefits of early detection come from diagnosing people before their cancer becomes advanced. If people are diagnosed before their cancer reaches a late stage, treatment can be more effective and outcomes are often better.

What the researchers looked at

The researchers compared the number of cancers found in people who had the blood test (test group) with the number of cancers found in people who did not have the test (control group).

The researchers first looked at the number of late-stage cancers overall. This was the main goal of the trial.

The researchers also looked at cancers found at the most advanced stage and at early stages.

Looking at stage 3 and 4 cancers together gives an overall picture of late-stage cancers. Looking at stage 4 cancers on their own focuses on the most serious cancers.

The researchers looked first at a group of 12 types of cancer that can grow quickly and are often found at a late stage. The researchers also looked at all cancer types together.

Why did the researchers measure stage 4 cancers, as well as stage 3 and 4 together?

Show answer

Cancers are often grouped by stage. Stage 1 and 2 are called early stage, and stage 3 and 4 are called late stage. Stage 4 cancers are the most advanced. Cancers found at a later stage can be harder to treat. Treatments have improved over time, and some stage 3 cancers can now be treated more effectively. 

What are the 12 types of cancers the researchers looked at first?

Show answer

The 12 types of cancer are: 

• Anus (where the bowel connects to the outside of the body) 
• Bladder
• Bowel
• Head and neck
• Liver and bile duct 
• Lung
• Lymphoma (a type of blood cancer) 
• Oesophagus (food pipe)
• Ovary
• Pancreas
• Plasma cell neoplasm (another type of blood cancer)
• Stomach

These cancer types can grow quickly and are often found at a late stage.

What the results show

The results showed that there was no difference in the number of late-stage cancers overall (stage 3 and stage 4 together). This means that the trial did not meet its main goal. There were fewer of the most advanced cancers (stage 4), and more early stage cancers (stage 1 and 2) in the group who had the test.

The researchers started by looking at late-stage cancers in the group of 12 cancer types. There was no significant difference in the number of stage 3 and stage 4 cancers found in the test group compared with the control group. There were 14% fewer stage 4 cancers in the test group.

Fewer late-stage cancers were seen the second and third time people had the blood test, both for stage 3 and stage 4 cancers together and for stage 4 cancers only.

Similar reductions were seen when all cancers were looked at together.

The researchers then looked at early stage cancers for the group of 12 cancers. They found that there were 16% more stage 1 and 2 cancers in the test group.

What the results mean

There were fewer of the most advanced cancers (stage 4) in the group who had the test. Stage 4 cancer can be difficult to treat. With advances in treatment, some stage 3 cancers can now be treated successfully. The trial did not meet its main goal of showing a difference in late-stage cancers overall (stage 3 and stage 4 together). 

The researchers are not sure yet why they saw fewer advanced cancers (stage 4 cancers) in people who had the test but not fewer late-stage cancers overall (stage 3 and 4 combined). They did find that there were more stage 3 cancers in the test group than the control group, especially after the first time people had the test. This could mean that the reduction in stage 4 cancers was outweighed by an increase in stage 3 cancers, so that no overall reduction was seen in stage 3 and 4 cancers together.

More late-stage cancers were seen in the test group than the control group the first time people had the test (‘prevalent’ screening round). This might be because the first time a group of people has a screening test, the test detects existing cancers. Some of these existing cancers might have been there for some time and progressed to a late stage. The following times a group has a screening test, the cancers found are more likely to have developed since the previous test.

The researchers are going to look again at if the test helped find cancer earlier. This will use an extra 12 months of data. The trial team is already collecting this data and will continue to do so. Looking at more data over time will help researchers understand the results better.