Should People Avoid Whole-Body Screening Info?

The most controversial part of last week’s article on the Midjourney ultrasound scanner was medical experts’ recommendation against whole-body screening (including existing whole-body screening technology using MRI).

Isn’t this crazy? Whole-body screening can save lives by detecting serious diseases like cancer. The experts counterargue that it finds so many false positives - minor zit-like imperfections that would never have caused problems, but which cost patients time, money, anxiety, and side effect burden to investigate - that it ends up net negative. But isn’t this just a problem of setting thresholds correctly? Can’t you commit to only investigating the most obviously bad things, then ignore the rest?

This seemed like an interesting problem to investigate in more depth, so I’ve tried to get numbers. These are rough estimates loosely based on parameters extracted from unsatisfactory studies1 - please don’t take them seriously as exact values, just as right-order-of-magnitude estimates. We’ll focus on whole-body MRIs, since this is a well-studied existing technology, then speculate later on how the results might generalize to whole-body ultrasound.

For every 1,000 seemingly-healthy people who get whole-body screening MRIs:

• 680 look fine and no follow-up is needed.

• 300 have mildly concerning findings. They’re told to follow-up with specialists, get further tests, or come back for more imaging later.

• 20 have extremely concerning findings and get immediate biopsies (surgeries to collect tissue samples from the area).

• Of those 20 people who got biopsies, 10 turn out to really have some serious disease. This is usually cancer, and for simplicity we’ll focus entirely on cancer going forward.

• Of those 10 cancer patients, 4 end up living longer and healthier lives because their cancer was detected early. The other six either have such slow-growing cancers that they would never have noticed before dying of something else, or such deadly cancers that detecting them early doesn’t help, or would have been found by standard screening so soon afterward that the extra screening didn’t buy meaningfully more time.

• Meanwhile, the 300 people who followed up with specialists and got extra tests will spend some number of years seeing more doctors and getting more tests and waiting and seeing, and eventually for 4 of them this will result in detecting some dangerous condition in a way that causes them to live longer and healthier lives.

So in total, 8 of the 1,000 people have benefited. The average benefit among those 8 people is 4 quality-adjusted life-years, so the total benefit from the scans is ~32 QALYs.

What’s the total cost?

• The original 1,000 scans cost about $2K each, and each takes about 3 hours of patient time (one hour for the scan itself, but we add two hours for driving, waiting, arranging the appointment, etc).

• The 300 patients who follow up each cost about another $2K in extra scans, tests, and doctor visits, and let’s say this takes them each ten hours (probably over the course of several years; some of what they’re doing is waiting and seeing whether the anomaly gets bigger vs. goes away). Rare and minor side effects of the testing might contribute -0.005 QALYS per person.

• Additionally, these people are anxious. 29% of them report “moderate” or “severe” distress. It’s easy to trivialize this and round it off to meaningless, but it’s doesn’t feel trivial when it’s happening to you or a loved one. In my day job as a psychiatrist, I sometimes encounter patients having mental breakdowns (the polite term is “adjustment disorder”) over potential cancers that they’ll have to wait six months to retest. The literature quantifies this as an average cost of 0.01 QALYs per uncertain test result.

• The 20 biopsies each cost about $5K and take about 10 hours. Biopsies are pretty minor as surgeries go, but there’s always some risk of post-surgical complication, and in the end these probably cost 0.04 QALYs each. Add the extra 0.01 for anxiety, and it’s a total of 0.05.

• We’ll very optimistically assume that there’s no extra cost to being diagnosed with a cancer that doesn’t require extra early treatment. The doctor says “You have cancer, but it’s a very slow cancer that will take thirty years to harm you, and you’re eighty years old, so this doesn’t matter. Just be chill.” This doesn’t always work in real life, but we’re trying to imagine a best-case scenario.

• We’ll very optimistically assume that after enough tests, the smartest doctors can distinguish cancers that should be treated and cancers that shouldn’t be treated with 100% accuracy, or at least that the number of cancers caught according to the above statistics is at some threshold where falsely identifying a cancer as treatable is rare.

• We’ll assume that the extra cost of treating the treatable cancers is zero. Why assume this? Because if we didn’t detect the cancer early, we would have detected it later, and still had to treat it, and the cost of treating small early cancers is probably no worse - and likely better - than the cost of treating large late cancers (even though treating the latter is less likely to work). So zero is actually close to an upper bound!

So total costs are $2.7 million, 6,200 hours of patient time, and 5 QALYs.

32 QALYS ←→ $2.7 million + 6,200 hours + 5 QALYS
27 QALYS ←→ $2.7 million + 6,200 hours
25 QALYs ←→ $2.7 million
$108,000 per QALY

So, converting everything to the same units, whole-body screening costs $108,000 to save one quality-adjusted life year. Usually in health economics, $100,000 per year of healthy life saved is considered the bar for a good cost-effective intervention (though other sources say $150,000). So this is somewhere around the bar, not unambiguously good or bad.

Could we improve this number by refusing to follow up on ambiguous results?