A single blood test picked up 17 types of cancer in a study of nearly 36,000 adults, and more than half of the newly diagnosed cancers it found were caught at stage 1 or 2.
The PATHFINDER 2 study, published in Nature Medicine, followed 35,878 adults aged 50 and over who took a multicancer early detection test developed by the company GRAIL.
The test looks for signals in fragments of DNA in the blood and can flag 17 broad types of cancer, including ovarian, lung, breast and colorectal.
Its biggest promise is in the gaps. Nearly three in four of the cancers it found, 72.8%, were types with no established screening recommendation, the ones most likely to go unnoticed until symptoms appear.
“One of the challenges in cancer screening is that most cancers do not have an established screening test,” said Dr. Karthik Giridhar, a medical oncologist at Mayo Clinic.
Of the newly diagnosed primary cancers, 53% were at stage 1 or 2 and 70.9% were at stage 1, 2 or 3, when treatment options are generally better.
Among the 32,007 people whose results were analyzed, false alarms were rare, with a specificity of 99.64%. When the test did flag a cancer signal, it was right 60.3% of the time.
The study has limits. It had a single arm with no comparison group, and it used an earlier version of the test that has since been replaced by a newer one on the market.
Giridhar is clear about where the test fits for now.
“These tests are not yet a substitute for established cancer screenings. Instead, they may supplement existing screening approaches and help expand understanding of cancer detection,” he said.
