Smart Screening & Dumb Screening
The big news of the day on my radar is the news that the American Cancer Society is cautioning that there may be a thing as too much screening, particularly for prostate and breast cancers. The New York Times has the story. The ACS's recommendation is based on the work of Dr. Laura Esserman, a professor of surgery and radiology at the University of California, San Francisco, and Dr. Ian Thompson, professor of urology at The University of Texas Health Science Center, San Antonio. The killer quote: “We don’t want people to panic,” said Dr. Otis Brawley, chief medical officer of the cancer society. “But I’m admitting that American medicine has overpromised when it comes to screening. The advantages to screening have been exaggerated.”
I've had the opportunity to hear both of these researchers speak, and they are smart eggs - and I'm thrilled that their work is getting such coverage. Dr. Thompson's work, for instance, is discussed in my forthcoming book (This is one of those stories that I'm thrilled to see, on the one hand, because it dovetails so neatly with what's in the book - while also a little chagrined to see, as an idea in the book gets wide currency before the book is out!).
Screening tests are one of the great tools of public health, where we can detect disease before it makes itself known. But there's a distinction between what I call "dumb screening" and "smart screening." Dumb screening is the idea that, given the tools, medicine should root out cancer whereever it lurks in whatever form, no matter the cost (to the psyche or the pocketbook). Smart screening, on the other hand, is the growing notion that all cancers are not the same; that there are some that are lethal and some that are not, and what we need to do is deploy the right tools to spot the right cancers. It's a more delicate task, and a more difficult judgment to make. But really, it's the path of all science - moving away from simplicity and towards complexity.
In many situations, screening works. Some 30,000 children in the United States have been spared mental retardation because of PKU testing. A blood test used to screen for colon cancer—the second-deadliest form of cancer for men and women overall, even though, ironically, it’s among the easiest to screen for—has been shown to save as many as 10,000 lives in the United States annually. These are the sorts of results that make people evangelize about a new screening test, because it allows the possibility of changing the future, of plucking people off one course and setting them on another that promises a longer, healthier life.
And screening is only going to get more common for three reasons. First is the emphasis on preventive medicine, based on the recognition by the medical establishment and the US government that having an earlier warning saves lives and money. Second are an emerging class of risk-based conditions like metabolic syndrome and high cholesterol that bring with them a new checklist of routine tests. The third driver is technology itself: New proxies for proximity, such as CT scans and PET scans, give us a look deep inside the human body. These are tempting tools for screening large numbers of people for diseases that are otherwise invisible. Genetic tests, which skip over the imaging of our bodies and go straight to the molecular level of our cells, are another driver for implementing more screening tests.
If these technologies are deployed systematically and wisely, they can be a great boon to our health, both collectively and individually. But the fact is that screening tests aren’t always used wisely. Though a screening test can be the first step in a well-considered Decision Tree, a screening test without forethought can propel us into a zone of ambiguous probabilities and poorly calibrated risks.
In the case of prostate cancer, in particular, there's been a growing sense that screening has downsides that outweigh the benefits. One noteworthy approach is taken by a startup called Soar BioDynamics. Soar sells a decision-support tool for men who’re trying to make sense of their PSA test results. The idea is to discern what, exactly, besides cancer could produce a high PSA level, so men don’t move too quickly toward biopsy and removal, with all the latter’s egative consequences. Using the information from a man’s PSA test along with that from a few other easy tests and data points, Soar’s tool calculates the most likely scenarios for what’s happening inside a man’s body, ranging from an enlarged prostate, to an infection, to a lethal cancer. The calculations are presented as probability scores for diagnoses.
“We can cut way down on the false positives and eliminate detection of the cancers that aren’t progressing. You want to catch the bad stuff, but ignore the stuff you don’t need to know about,” says company founder Tom Neville. “The issue isn’t just what decisions you make, but what order you make them in. We’re trying to switch the order of events. There’s all this stuff driving people toward biopsy and treatment. We’d like to eliminate the unnecessary biopsies and only go to the expensive experts when it’s highly warranted. We’re not trying to do away with screening. The PSA test can be a valuable test, there’s a lot of information in there. But it’s important to know what the test actually shows.”
Soar charges for its service—$80 for one year of reports. But there are other, free tools out there that take a similar approach, turning research around so an individual can interrogate it for its applicability to his specific circumstances, rather than having to navigate through stacks of research papers and findings for some wisp of relevance. At the University of Texas at San Antonio, Dr. Thompson has developed a prostate risk calculator that lets a man enter his PSA level along with his age, race, family history, and a couple of other metrics and churns out his risk of developing prostate cancer. Importantly, the calculator also calculates the risk of a high-grade cancer, accounting for the fact that not all prostate cancers are lethal. The value of such a tool, Thompson said at a recent symposium hosted by the Canary Foundation, is that it turns the PSA figure from one isolated data point into one of many inputs. “We need to build in characteristics about the person, their age, their race, their family history,” says Dr. Thompson. “It’s not just what one test tells us.”
For a play-by-play look at how scientists trying to distinguish between smart screening and dumb screening, see my story on the Canary Foundation from Wired.