A Battle Brews Over Blood Tests for Cancer --- Positive results of an Exact Sciences study lead CEO of Guardant to challenge his rival to a bet

"Blood tests for cancer detection, known as liquid biopsies, can still be unreliable, but progress is being made. Competition between different diagnostics companies is intensifying.

In July, the Food and Drug Administration approved Shield, a colorectal cancer blood test developed by Guardant Health. Shield became the first blood test approved by the FDA as a primary screening option for colorectal cancer that meets performance requirements for Medicare coverage, the company announced at the time. But its first-mover advantage might not last very long: Competitor Exact Sciences, which sells the Cologuard stool test for the same disease, on Monday announced positive data for its blood-based study that arguably beat Guardant's test.

The company reported that its test caught 88.3% of cancers while detecting 31.2% of advanced adenomas, or precancerous polyps.

 Catching these polyps early is important because they could turn into cancer if left undetected. (That is why colonoscopies are still the gold standard: A doctor can pre-emptively and painlessly remove the polyps during the procedure.) 

In larger studies, Guardant and Freenome, another biotechnology company, detected the advanced adenomas less than 15% of the time. That could give Exact Sciences a major advantage. On Monday, Guardant stock fell 5.3% while Exact Sciences gained 6%. (Freenome is privately held.)

The data come with a major caveat, though: The results are from a relatively small study of about 3,000 samples. To feel more confident that Exact's test is superior, Wall Street will want to see the data from a 20,000-plus adult study the company is conducting. Results from that study, necessary for FDA approval, are expected in the first half of next year.

"While these results are better than investor expectations per our survey, the whole focus is what they portend for the final FDA readout, and how much degradation we could see from partial case control to final readout," wrote TD Cowen analyst Dan Brennan.

At this juncture in a drug or medical product's development, rivals usually keep quiet or say something generic about how it is good to have more options for patients while cautioning that more data are needed. They typically focus their messaging on how their approach might be best for the patient. Guardant's co-founder and co-chief executive took a less-orthodox approach: In a LinkedIn post, AmirAli Talasaz challenged Exact Sciences CEO Kevin Conroy to a $1 million bet that the data presented on Monday won't hold up in the bigger trial.

Exact Sciences management had already warned that the final results might be less impressive. But Conroy has argued it should still hold up well, while cautioning during a second-quarter earnings call that "we can't guarantee it, it's science."

TD Cowen's Brennan points out that the large market of 60 million unscreened Americans leaves room for multiple players. And while more tests are great news for patients, one with greater accuracy could be worth considerably more than a million dollars." [1]

1. A Battle Brews Over Blood Tests for Cancer --- Positive results of an Exact Sciences study lead CEO of Guardant to challenge his rival to a bet. Wainer, David.  Wall Street Journal, Eastern edition; New York, N.Y.. 18 Sep 2024: B.13.