I read a blog post yesterday about pros/cons of CTs for lung cancer screening. It’s here– and has good info on the risk benefit calculations to consider for that test.
BUT- the 4 points brought up are useful to consider for any screening test, so I thought I’d review them here as well.
1- Harm from the test itself. In the case of CT scans, mammograms and other radiological tests, there is a potential for malignancy developing from the test itself. We don’t really know what the risk is from low dose CT, but it exists. Even blood draws (for PSA or lipid panels) carry some, albeit quite small, risk.
2. False positives. We talk about this often with screening tests- they are set up to have a high sensitivity, often at the expense of specificity. It is important to tell your patients (and remember yourself) that a positive test does not necessarily = bad diagnosis. The next step to evaluate a positive test may be quite invasive- not sure about you, but I wouldn’t sign up for a bronch or VATS just for funsies.
3. Incidentalomas. Slightly different from #2, you may find something that you weren’t looking for, yet have to evaluate further. This was 1 out of 13 patients in the CT for lung cancer screening study. That’s a lot of further testing.
4. Overdiagnosis. This is the hardest to explain, but may be more important than we realize. Most folks, if there is a cancer, want it out- want a cure. But many cancers may be slow growing and never cause a problem. We are more comfortable with this concept in prostate cancer, but it exists in breast cancer, and likely lung cancer as well. The treatments for these disease are painful, exhausting, and maybe even life threatening in and of themselves. First, do no harm.
So, we like screening in general medicine, but more and more, we are learning that it’s not all it’s cracked up to be.