I have been scoped, X-Rayed, Ct scanned, sampled for pathology, and likely something I have forgotten. So today I get a PET scan. They inject some radioactive stuff in me and I set for an hour without even any old magazines to read while any cancer I have hogs the radioactive stuff. Then about a half hour inching through a tube. So any tumors I have should have picked up the radioactive stuff and show up on the scan. It really sounds like a good way to track down cancer wherever it is. So why are we doing so many other tests that only find certain cancer and why are we finding so many cancers after they are harder to cure?
There isn’t just one type of PET scan. To you as a patient, they may seem mostly the same, but the radioactive materials they use differ, and they often mix the radioactive stuff with particular types of non-radioactive stuff to get it to go where they want. They are often very specific tests. They aren’t the general purpose “cancer finding” tests that you seem to think they are.
For example, technetium attached to methylene-diphosphonate will be picked up by your bones and will make any bone cancers quite evident, but won’t show squat for something else, like a thyroid cancer for example. Iodine-123 will show the thyroid cancer, but won’t show the bone cancer. If they think you have liver cancer, a nuclear medicine test probably won’t show anything better than an MRI would show. You would be better off getting an MRI done because at least with that you aren’t being unnecessarily exposed to radiation.
What test did you have done, by the way? Do you know what they injected you with?
It isn’t. It’s a really good way of identifying metabolically active tissue - but lots of things besides cancer can produce hot spots on PET, and the subsequent biopsy which has to be done to confirm that the hot spot IS in fact a cancer and not just an inflammatory process isn’t harmless. And a PET scan involves exposure to radiation, which is itself a carcinogen.
PET scans are definitely useful, but used as a first-line screening tool they’d almost certainly hurt more people than they help. Which is why they’re not used as a primary screening tool.
Also, seeing as many of the radioactive isotopes have a non-negligible half-life, there’s the very real possibility that once you’re out of the hospital, you’re going to scare the bejeezus out of some poor NSA geek watching radiation monitors at important spots. I’ve heard of a casino bus being pulled over and boarded because one of the little old ladies had gotten a thyroid PET scan a day or two previous.
Even those otherwise tiny levels of radiation are enough to set off alarms. It may be that the doctors, hospitals, technicians, suppliers, et al got tired of being screamed at for anything but the most necessary diagnostic cases.