ASCO21: Grail's pan-cancer early detection test may be ready to enter clinic

The most recent version of Grail's multi-cancer early detection (MCED) test was able to both accurately detect the disease and also predict where the cancer signal may be coming from in the body, according to a new analysis. Researchers say the findings, which will be presented at the upcoming American Society of Clinical Oncology (ASCO) conference, suggest the test could be ready for use in clinical practice.

Results from the ongoing PATHFINDER study on a previous version of a blood-based MCED test demonstrated favourable classification and test characteristics. The authors took a second look at the PATHFINDER samples as part of a pre-specified interim analysis to evaluate the more recent version, which has an updated classifier, and is planned for clinical implementation as a general multi-cancer screening tool.

In this latest analysis, investigators assessed the positive predictive value (PPV) for cancer detection, the overall cancer signal origin (CSO) accuracy and the concordance between the two test versions. A total of 4011 participants were evaluable. Cancer signal was detected in 38 participants, of which 27 also had signal detected by the previous version of the MCED test, including 19 who reached diagnostic resolution. This latter group broke down into 13 with a cancer diagnosis and six without. Meanwhile, the remaining 11 out of the 38 were discordant positives. Researchers noted that among the 13 patients with cancer, nine different cancer types were detected, including two cases at Stage 1 and three cases at Stage 2, while the accuracy of the top CSO prediction was 92.3%.

High concordance between test versions

"A conservative minimal PPV assuming all discordant positives are false positives was 43.3% based on 19 patients with diagnostic resolution and 11 discordant positives," the authors said. High negative percent agreement, at 99.7%, between the two test versions was seen. Meanwhile, positive percent agreement of 43.5% was "consistent with the more stringent threshold for hematologic signal in the recent MCED version, as most discrepant cases had haematologic CSO with the previous MCED test," the authors added.

Grail is in the process of being acquired by Illumina for $8 billion. However, the deal is facing antitrust scrutiny in Europe over the MCED test, which is called Galleri, while US regulators are taking Illumina to court in a bid to block the merger. For related analysis, see Wider View: Is Grail moving further out of Illumina's reach? and Wider View: Illumina not letting Grail go.

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