..and now breast cancer screening

Following last week's post on prostate cancer, here is one on breast cancer screening.

The basics are clear: breast cancer screening saves lives but also causes harm because of the stress and side effects of unnecessary operations in women who (a) didn't have breast cancer - false positives and (b) did have cancer but one which was never going to kill them - overdiagnosis.

The key problem is to put numbers on the benefits and the harms, so as to see which is greater.A trial is not feasible so you have to weigh it up using whatever data you can find. Table 1 in the paper helpfully shows the various data sources and estimates used in the calculations. One of the key variables is loss of "quality of life" while waiting for confirmatory tests after being told you have screened positive.