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Are Liquid Biopsies All They're Cracked Up to Be?

In an editorial in STAT, Brigham and Women’s Hospital cancer researcher and senior investigator H. Gilbert Welch expresses some skepticism about the benefits of liquid biopsy technology, and specifically about whether people will really benefit from the use of such testing for the early detection of cancer.

For the past 25 years, Welch says his research has focused on cancer screening, and he believes the benefits of cancer screening have been "systematically overstated and its harms largely ignored." While he doesn't doubt that liquid biopsy can find some aggressive, rapidly-growing cancers earlier, he's not as certain that multicancer liquid biopsy screening of the general population will help people live longer.

"Effective cancer screening requires more than early detection," Welch writes. "It also requires that starting therapy earlier helps people live to older ages than they would if they started treatment later. If that doesn't happen, liquid biopsies will only lead to people living longer with the knowledge they have a potentially incurable disease without extending their lives. These people would be subjected to cancer therapies and their toxicities earlier, but at a time when they would otherwise be experiencing no cancer-related signs or symptoms."

In fact, he adds, this would mean that screening would look helpful but not be helpful at all in some cases. Survival times and five-year survival rates always increase with screening, even if the age of death is unchanged, because those metrics are measured from time of diagnosis. But they don't help the patient live longer. 

Welch believes the only way to work this all out is to do a randomized trial that would randomly assign participants to either receive liquid biopsy screening or no screening, then follow them for a set number of years, and compare the death rates in the two groups.

"The only thing that is clear to me [right now]," he adds, "is that [liquid biopsies] will cost a lot of money. That's another thing the companies and their investors are banking on. The Galleri test costs $949 a pop and is recommended every year in those 50 and older. With 100 million Americans in this age group, that’s about $100 billion a year — 15 times the budget of the Centers for Disease Control and Prevention. And that's not even counting the cost of all the subsequent testing and treatment that will invariably follow."