Early Detection Blood Test May Change Cancer Screening Paradigms

New results from the PATHFINDER clinical trial suggest that a multicancer early detection blood test can accurately identify the presence of cancer in apparently healthy people. The test, known as Galleri (developed by GRAIL), uses cell-free DNA and machine learning to detect a common cancer signal across more than 50 cancer types as well as to predict cancer signal origin. Once the test is validated and refined further, it may revolutionize the way in which cancer is diagnosed and treated.

“As this technology develops, people must continue with their standard cancer screening, but this is a glimpse of what the future may hold,” commented lead investigator Deb Schrag, MD, MPH, George J. Bosl Chair, Department of Medicine, Memorial Sloan Kettering Cancer Center, and Professor, Medicine, Weill Cornell Medical College, New York City, who presented the findings at the European Society for Medical Oncology Congress 2022. “What is exciting about this new paradigm is that many of these were cancers for which we don’t have standard screening,” she added.

Study Details

For the PATHFINDER study, the Galleri test was used in 6621 healthy individuals aged ≥50 years, with or without additional cancer risk factors, such as a history of smoking or genetic risk. The test identified a positive cancer signal in 1.4% (N = 92) of participants with analyzable samples. None of the individuals who tested positive had any evidence of cancer at the time of testing. Subsequent work-up, which could include scans and/or biopsy, found cancer in 38% of those with a positive test.

A total of 90 participants underwent diagnostic testing (33 true positives and 57 false positives). Of the true positives, 81.8% had more than 1 invasive diagnostic test, as did 29.8% of the false positives.

Among the 6290 participants who were cancer-free, 99.1% received a negative test result. Of those with a positive test result, the median time to achieve diagnostic resolution (ie, to find cancer or determine there was no evidence of malignancy requiring further investigation) was 79 days. Among participants with a positive screening test, diagnostic resolution was achieved within 3 months for 73%.

The cancer types diagnosed included 19 solid tumors and 17 hematologic malignancies. Seven were diagnosed in individuals with a history of cancer, 26 were cancer types without standard screening, and 14 were diagnosed at an early stage.

“The results are an important first step in early cancer detection tests, because they showed a good detection rate for people who had cancer and an excellent specificity rate for those who did not have cancer. In people with a positive test, it took less than 2 months to confirm the diagnosis of cancer and it took a bit longer if they did not have cancer, primarily because physicians opted to perform imaging studies and then repeat them a second time months later to investigate the possibility of a cancer diagnosis,” Dr Schrag said.

“An important finding was that few participants with a false-positive screening test required multiple invasive procedures such as endoscopies and biopsies. This finding should help to allay concerns that these tests could cause harm by generating unnecessary procedures in people who are well,” she added.

Dr Schrag stressed the importance of continued standard screening for tumors, such as breast and colorectal cancers, while multicancer early detection tests continue to be refined and validated for cancers such as pancreatic, small bowel, and stomach cancers, for which there are currently no screening options available.

Although the Galleri test is now available in the United States and offered by several US health networks, it is not approved by the FDA and is not covered by medical insurance, so individuals must pay approximately $950 for it out of pocket.

Dr Schrag noted that it is not clear at this time whether the test will be cost-effective. “This technology is not ready for population-wide screening, but as the technology improves, costs should go down,” she said.

Key Points

  • In PATHFINDER, a multicancer early detection blood test identified a cancer signal in 1.4% of 6621 people aged ≥50 years who were not known to have cancer, and cancer was confirmed in 38% of those with a positive test
  • Of 6290 individuals who were cancer-free, 99.1% received a negative test result
  • Among those with a positive test result, the median time to achieve diagnostic resolution was 79 days
  • Among participants with a positive screening test, diagnostic resolution was achieved within 3 months for 73%

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