Taking Action

Dr Hall suggested a test like Galleri could have incredible value. As a blood test, this is something that could be performed at any doctor’s office, compared with existing screening methods that are more expensive and often require patients to go to specific locations.

Dr Hall also pointed out that the test has a low failure rate (0.8%) and a low false-positive rate (0.5%).

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“This study tells us that the technology is pretty powerful at ruling out cancer,” Dr Hall said. “If you don’t actually have cancer, the likelihood that the test would tell you that you do have cancer is very small, which is very reassuring.”

Dr Klein said the goal would be to use this test in the general population of people who are at risk for cancer.

“The average person is not at risk until they reach age 50 if you look at cancer incidence across all cancers,” Dr Klein said. “Maybe this test could be recommended at regular intervals.”

Another potential population for this type of test is people who have inherited a syndrome that puts them at higher risk for developing cancers, such as BRCA mutation carriers or families with Lynch syndrome.

“We are not there yet,” Dr Klein said, “but this current study opens the door to this possibility.”

More to Learn

Dr Klein said the CCGA studies were the first set of studies to test this multicancer early-detection technology. The next series of studies will assess its utility in some of the intended-use populations.

For example, the PATHFINDER study (ClinicalTrials.gov Identifier: NCT04241796) was designed to assess the implementation and performance of the screening test in individuals aged 50 years or older.

Interim results from PATHFINDER showed that the test accurately detected 29 cancers across 13 types.3,4 The positive predictive value was 44.6%. When cancer was confirmed, the accuracy of the test for detecting the cancer signal origin was 96.3%.

“We also have to look more closely at the false-negative rate and false-positive rate, and what harm comes to patients from having a positive test and being subjected to further diagnostic evaluation,” Dr Klein said.

Specifically, research is needed to evaluate patients with a positive screening test in whom no cancer is found by standard diagnostic modalities.

“What does that mean? Is the test so sensitive that it picked up a tumor that standard blood and imaging tests can’t even see yet, or is it a true false positive?” Dr Klein asked. “It will take some time to sort that out.”

Despite that, Dr Klein and Dr Hall were excited about the potential of this screening test.

“One of the things we are nervous about in the cancer community is we are seeing the age of cancers shifting lower and lower,” Dr Hall said. “We have questioned if we then need to shift screening ages down. Maybe we could use a test like this to noninvasively screen that younger population and, if something is found, send just those people for more targeted screening.”

Dr Hall agreed that more studies are needed, especially studies to test whether this additional screening leads to lives saved.

Disclosures: This research was supported by GRAIL, Inc. Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.


  1. Klein EA, Richards D, Cohn A, et al. Clinical validation of a targeted methylation-based multi-cancer early detection test using an independent validation set. Ann Oncol. Published online June 23, 2021. doi:10.1016/j.annonc.2021.05.806
  2. Blood test for early detection of cancer: Final study results support screening use. News release. European Society for Medical Oncology (ESMO). June 25, 2021. Accessed July 27, 2021.
  3. GRAIL presents interventional PATHFINDER study data at 2021 ASCO Annual Meeting and introduces Galleri, a groundbreaking multi-cancer early detection blood test. News release. GRAIL, Inc. June 4, 2021. Accessed July 27, 2021.
  4. Beer TM, McDonnell CH, Nadauld L, et al. Interim results of PATHFINDER, a clinical use study using a methylation-based multi-cancer early detection test. J Clin Oncol. 2021;39:(suppl 15; abstr 3010). doi:10.1200/JCO.2021.39.15_suppl.3010