The Bad Math of CT Scans


There’s bad math behind using CT scans for lung cancer screening. For every batch of 320 people, screening prevents one death while over-diagnosing 1.38 (Patz Jr et al 2013).

In the business world, those kind of numbers are called “a negative ROI”. It’s somewhat like giving mountains of cash to CEOs despite cratered leadership. And if my CEO is overpaid, I’m annoyed; not directly harmed. On the other hand, overusing poor-performing CT scans leads to damaged benelles.

Let’s put aside finance for a minute and look at health outcomes.

Over-diagnosing leads to negative health outcomes. False-positives and positive-positives alike shock the heart and central nervous system with anxiety and distress, and often lead to depression. Worst of all, over-diagnosing leads to unnecessary medical actions, like additional radiological scans, harmful medications, and surgeries.

It’s not a stretch to say that for every one life saved by screening for lung cancer, another life is taken away. For one thing, mortality increases with every unnecessary surgery. But the bigger factor is exposing millions of people to regular CT scans, increasing their lifetime DNA damage and chances for cancer.

Unfortunately, our medical system is not transparent about the risk of radiation. We are trained to think that regular screening is the most intelligent approach. In reality, each CT scan is the functional equivalent of about one year’s intake of radiation. In less than 30 minutes.

Our bodies were designed to intake small doses of radiation over months and years. They were not designed to intake relatively-large, internal doses of radiation all-at-once.

Even if you side with the radiation people, the math still doesn’t make sense. Let’s say you start getting one proactive chest CT scan per year at the age of 40. Since one CT scan is the equivalent of one year’s natural radiation intake, this means that by age 60, you’ll have the chest of an 80-year-old. 80-year-olds have a much higher chance of getting cancer than 60-year-olds. Which means that you’ve spent a small fortune to increase your chances of cancer, in the name of avoiding cancer.

Current research clearly indicates that CT scans use far more radiation than they need to, and also that small doses of radiation cause significant and measurable increases in cancer risk.

The numbers don’t support proactive lung cancer screening. I doubt the numbers will support any type of radiation-based, proactive cancer screening. Ripping-up healthy DNA to get a snapshot of our organs is not a good trade-off. It’s barbaric.

Not until the medical industry gets serious about finding creative ways to scan with little-to-no radiation will proactive screening make sense. That kind of innovation would require new government regulations on radiation exposure, plus government research money to develop new technologies to meet the regulations. Such innovation is decades away, thus the healthy approach is to protect benelles by declining proactive radiological screening.


Patz EF Jr, et al “Overdiagnosis in low-dose computed tomography screening for lung cancer” JAMA Intern Med 2013; DOI:


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