A new blood test for cancer has raised hope for early detection, but Scientists warn it has serious limits and should not replace regular cancer screenings.
The test, called Galleri and made by U.S. company Grail, was studied in more than 23,000 people over the age of 50 who had no previous cancer. It can detect signals from around 50 different types of cancer. In the study, about 62 percent of people who tested positive were later confirmed to have cancer.
The test also correctly gave a negative result to 99.6 percent of people who did not have cancer. At first glance, these results seem very promising.
However, Scientists say the test misses many cases. Its sensitivity to the ability to find people who actually have cancer was only about 40 percent. This means it failed to detect roughly three out of every five cancer cases in the study.
This low sensitivity is a major concern. A negative result does not guarantee that a person is cancer-free. People who get a negative test result might feel safe and delay regular screenings or check-ups, which could let cancer grow unnoticed.
Another concern is false positives. Even though they are rare, if the test is used widely, thousands of people could be told they might have cancer when they do not. This could lead to worry, stress, and unnecessary tests that are costly or invasive.
The price of the test is also high. In the U.S., one Galleri test costs about $949. Scientists also point out that there is no proof yet that using the test will lower the number of deaths from cancer, the main goal of any screening tool.
The Galleri blood test is a step forward in cancer detection, but it is not perfect. Scientists say it should be used alongside, not instead of, regular cancer screenings and check-ups.
