Summary: GRAIL’s Galleri multi-cancer early detection (MCED) test demonstrates strong clinical performance in preferentially identifying aggressive prostate cancers, reducing the risk of overdiagnosis of indolent cases.

Takeaways:

  1. Focused Detection: The Galleri MCED test successfully identified clinically significant, aggressive prostate cancers while minimizing detection of low-grade, indolent cancers that often lead to overdiagnosis.
  2. High Accuracy: The test showed over 90% accuracy in predicting the cancer signal origin for prostate cancers, with most detected cases being intermediate to high-grade and in advanced stages (III or IV).
  3. Implications for Screening: The study supports the use of the Galleri test in population-based screening programs as an adjunct to standard-of-care, emphasizing the need for prompt diagnostic evaluations when a prostate cancer signal is detected.

GRAIL, a healthcare company whose mission is to detect cancer early when it can be cured, announced that detailed findings of the performance of its Galleri multi-cancer early detection (MCED) test in prostate cancer were published in JCO Precision Oncology. 

The data support the clinical performance of the Galleri test to preferentially screen for aggressive, clinically significant prostate cancer as compared to slow-growing (indolent) cases in the Circulating Cell-free Genome Atlas (CCGA) and PATHFINDER studies.

“All screening tests run the risk of overdiagnosis. In the case of prostate cancer, this is largely due to the high prevalence of low-grade, indolent cancers,” says Brandon Mahal, MD, a radiation oncologist at Sylvester Comprehensive Cancer Center, part of the University of Miami Miller School of Medicine, and lead author of the study. “The results of this study demonstrate that the use of MCED tests in a population-based screening program is unlikely to contribute to overdiagnosis of slow-growing prostate cancers that may not need treatment. That being said, clinically validated MCED tests like Galleri reveal that when a prostate cancer signal is detected, it usually indicates aggressive disease and additional diagnostic evaluation is necessary.”

Detecting Prostate Cancers

The published data is from an analysis of 420 prostate cancer patients identified in the independent clinical validation portion (substudy 3) of the multi-center, case-control observational study Circulating Cell-free Genome Atlas (CCGA) study and 18 cases from the prospective intended-use PATHFINDER study. The data were previously presented at the American Association for Cancer Research (AACR) Annual Meeting in March 2024. 

Results from this analysis showed that of the prostate cancers that were detected by the MCED test, most were clinically significant (93% were intermediate or high grade and 67% were stage III or IV). For detected prostate cancers, the cancer signal of origin (CSO) prediction accuracy was > 90%. Detectability for stage I and II cancers were 4.2% across both studies combined, which is expected with low shedding prostate cancer tumor fraction and is consistent with cfDNA literature in prostate cancer. Test sensitivity of prostate cancer for all stages was 11.2% in substudy CCGA-3. Notably, the MCED test detected no low-grade cancers, 1.9% of intermediate-grade cancers, and only 4.2% of stage I and II cancers across both studies combined. Of the detected cases, 93% were Gleason grade groups 3-5. This analysis demonstrates the MCED test preferentially detects high-grade, clinically significant prostate cancer. This is important because an MCED test, when used in addition to standard-of-care screening, should not exacerbate overdiagnosis of indolent cancers. These findings also suggest that individuals with a cancer signal detected and a prostate CSO prediction should undergo a prompt diagnostic evaluation to determine the presence of aggressive disease for which treatment is generally indicated1.

“This prostate cancer analysis underscores the power of Galleri in a general population of men at-risk for prostate cancer as it is able to detect biologically significant cancers that need treatment without potentially contributing to the burden of overdiagnosis,” says Eric Klein, MD, distinguished scientist at GRAIL and an author on the study. “The very high accuracy of the cancer signal origin prediction for prostate cancer indicates the need for a prompt diagnostic work-up in those with a cancer signal detected.”

References

  1. “Initial Treatment of Prostate Cancer, by Stage and Risk Group.” American Cancer Society, 22 Nov. 2023, www.cancer.org/cancer/types/prostate-cancer/treating/by-stage.html.