Blood test could detect cancers in early stages
Scientists are reporting progress on a blood test to detect many types of cancer at an early stage, including some of the most deadly ones that lack screening tools now.
Many groups are working on liquid biopsy tests, which look for DNA and other things that tumours shed into blood, to try to find cancer before it spreads, when chances of cure are best.
In a study Thursday in the journal Science, Johns Hopkins University scientists looked to see how well their experimental test detected cancer in people already known to have the disease. The blood tests found about 70 per cent of eight common types of cancer in the 1,005 patients.
The rates varied depending on the type — lower for breast tumours but high for ovarian, liver and pancreatic ones.
In many cases, the test narrowed the possible origin of the cancer to one or two places, such as colon or lung, important for limiting how much followup testing a patient might need. It gave only seven false alarms when tried on 812 others without cancer.
The test is nowhere near ready for use yet; it needs to be validated in a larger study already underway in a general population, rather than cancer patients, to see if it truly works and helps save lives — the best measure of a screening test’s value.
“We’re very, very excited and see this as a first step,” said Nickolas Papadopoulos, one of the Hopkins study leaders. “But we don’t want people calling up” and asking for the test now, because it’s not available, he said.
Some independent experts saw great promise.
“It’s such a good first set of results” that it gives hope this approach will pan out, said Dr. Peter Bach, a health policy expert at Memorial Sloan Kettering Cancer Center who consults for a gene testing company. “Anything close to 50 per cent or 40 per cent detection is pretty exciting stuff,” and this one did better than that, he said.
Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society, was encouraged that the test did well on cancers that lack screening tests now. If a blood test could find 98 per cent of ovarian cancers at an early stage, as these early results suggest, “that would be a significant advance,” he said.
But he cautioned: “We have a long way to go to demonstrate its effectiveness as a screening test.”
The test detects mutations in 16 genes tied to cancer and measures eight proteins that often are elevated when cancer is present.
It covers breast, colon and lung and five kinds that don’t have screening tests for people at average risk: ovarian, liver, stomach, pancreatic and esophageal. Prostate cancer is not included. A blood test already is widely used — the PSA test — but its value for screening is controversial.
Researchers tried the new test on people whose cancers were still confined to where it started or had spread a little but not widely throughout the body.
It detected 33 per cent of breast cancers, about 60 per cent of colon or lung cancers and nearly all of the ovarian and liver ones. It did better when tumours were larger or had spread. It did less well at the very earliest stage.