Prenuvo: The Turtle Catcher

Excellent piece on Prenuvo’s whole body scans by Dr. Dhruv Khullar in The New Yorker:

Doctors sometimes use a barnyard analogy to talk about the vast differences between cancers. A tumor can be a turtle, a bird, or a rabbit, depending on its speed and ability to escape; the goal of screening and treatment is to fence the cancer in. Turtles move so slowly that, fence or no, they’ll never make it out. Birds are so flighty that fences are irrelevant; even if you spot them, there’s no real way to stop them. Only the rabbits can actually be fenced in. By some estimates, at least a quarter of cancer diagnoses can be considered overdiagnoses. These tumors are turtles; they never would have left the barn.

South Korea inadvertently illustrated this point when a government program, starting in 1999, offered free screenings for several common cancers. A thyroid-cancer screening wasn’t included, but many patients opted to add one for a fee. Between the early nineties and the early twenty-tens, rates of thyroid cancer soared fifteenfold—a development that would have been worrying, except that death rates from thyroid cancer never rose, and remained very rare. Diagnosing these cancers wasn’t saving lives: almost all were papillary thyroid tumors, which are present in as many as a third of all adults and rarely cause problems. Nonetheless, tens of thousands of South Koreans had their thyroids removed and started taking lifelong hormone supplements. They’d fenced in turtles.

Excellent, accessible illustration of what screening is for and why more isn’t always better. There will always be happy individual narratives of people saved by screening even when, on the whole, a particular screening test is net harmful. Judging a population tool that results in society-wide costs based on individual unaggregated results is a fool’s game.

Quoting a scene from Scrubs, the most accurate medical television show of all time:

In a 2004 episode of the sitcom “Scrubs,” Bob Kelso, the chief of medicine at Sacred Heart Hospital, runs into a fellow-doctor, Perry Cox, in the hallway. “I am considering offering full-body scans here at Sacred Heart,” Kelso says. “What do you think?”

Cox looks appalled. “I think showing perfectly healthy people every harmless imperfection in their body, just to scare them into taking invasive and often pointless tests, is an unholy sin,” he says.

“Does sound a little sketchy ethically, doesn’t it?” Kelso says. “Thanks, Perry.”

It’s feasible there could be a future world where very frequent low-cost whole-body screening is helpful, particularly if the follow-up for turtles was nearly always just more low-cost whole-body screening and not something costly and/or invasive. But today, in our current strained inefficient system with its high costs–and its current players and their financial motives–this is unlikely to be the case.

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