A newly developed blood test can spot more than 50 types of cancer and identify the tissue in which the tumor originated, according to a study published in the medical journal Annals of Oncology.
With a false-positive rate of less than 1%, the test appears to be more accurate than some screenings such as mammograms, raising the prospect that it could be included in national cancer screening programs.
In the study, which was funded by the maker of the first-of-its-kind blood test, California-based GRAIL Inc., researchers found the diagnostic was able to correctly pinpoint the tissue in which the cancer originated in 96% of samples and was accurate in 93% of those samples.
The blood test focuses on about 1 million out of the 30 million sites in the human genome where methylation — chemical changes to the DNA that can control gene expression — occurs. When abnormal methylation patterns develop, that can lead to gene expression that fuels cancer cell growth.
An algorithm was used to predict the presence of cancer and the type of cancer based on the patterns of methylation in the DNA cast off by tumors into the bloodstream. The algorithm analyzed blood samples from the participants to identify methylation changes and to classify the samples as cancer or noncancer, and to identify the tissue of origin.
'Most informative regions'
"Our earlier research showed that the methylation approach outperformed both whole-genome and targeted sequencing in the detection of multiple deadly cancer types across all clinical stages, and in identifying the tissue of origin," said Michael Seiden, a doctor and president of privately held, Texas-based US Oncology Inc., which operates a network of cancer practices.
"It also allowed us to identify the most informative regions of the genome, which are now targeted by the refined methylation test that is reported in this paper," said Seiden, who is also the paper's senior author.
The true positive rate was 67.3% across clinical stages I, II and III in the 12 deadliest types of cancer: anal, bladder, bowel, esophageal, stomach, head and neck, liver and bile duct, lung, ovarian and pancreatic cancers, lymphoma, and cancers of white blood cells like multiple myeloma.
"Considering the burden of cancer in our society, it is important that we continue to explore the possibility that this test might intercept cancers at an earlier stage and, by extension, potentially reduce deaths from cancers for which screening is either not available or has poor adherence," said Seiden. "To our knowledge, this is the largest clinical genomics study, in participants with and without cancer, to develop and validate a blood test for early detection of multiple cancers."
The test's limitations
The test had some limitations. All the participants with cancer had already been diagnosed, and the study was not designed to establish the test's impact on death from cancer or other causes. In addition, not all patients had been followed for a year at the time of this analysis — monitoring needed to ensure their noncancer status was accurate — and there were inaccuracies in the detection of the tissue of origin for cancers that are driven by the human papillomavirus including cancers of the cervix, anus, and head and neck.
"This is a landmark study and a first step toward the development of easy-to-perform screening tools," said Fabrice André, a breast cancer specialist and the editor-in-chief of Annals of Oncology. "Earlier detection of more than 50% of cancers could save millions of lives every year worldwide and could dramatically reduce morbidity induced by aggressive treatments."
André, who is also a professor of medicine at the Paris-Saclay University and director of research at France's Institut Gustave Roussy in Villejuif, added that although the numbers are still small, this new technology is particularly intriguing in pancreatic cancer, for which mortality rates are very high as it tends to be diagnosed in its later stages.
Researchers are continuing to validate the test in large, prospective studies in the U.S and in the U.K.
Grail's investors have included pharmaceutical giants Bristol-Myers Squibb Co. and Celgene Corp., which was bought by Bristol-Myers.