I have heard, from a recently minted M.D., the opinion that "it doesn't matter if breast cancer screening causes breast cancer, because once we detect it, we can treat it." I, lacking a medical degree, am obviously not smart enough to fathom this reasoning, how we should go around breaking people because we think we know how to fix them later?
Are you trying to say that screening for breast cancer is the only possible cause of breast cancer? Even if screening increases the number of cases by 1% (to use an arbitrary percentage), but reduces the death rate by 75% (to use another arbitrary percentage), that's still a net win.
It doesn't take a medical professional to understand simple math.
Unfortunately, the math and the concepts involved in screening decisions is not that simple. There are a number of situations where early or widespread screening can result in greater loss of life, and even more where the costs do not justify the expense. Currently there are debates worldwide over the "best" methods of screening for colon cancer as well as breast cancer because of this. Some factors that come into play for the breast cancer screening is what fraction of the detected cancers would prove to be fatal if untreated? What fraction of those undergoing treatment die due to the treatment (surgery, infection, anesthesia, etc. all have death rates). What is the false positive rate? Going beyond the simple death counting rate - how many "lives saved" should be balanced against the costs (money, time, fear, etc) that the screening produces?
The results or decisions to widely screen depend on: how common the problem being screened for is; how effective the screening is; what the false positive rate is; what the effectiveness of the treatment is (for both those with and without the condition); what the risks of treatment are (for both those with and without the condition); how dangerous the condition is untreated; how long it takes for the condition to progress; what the demographics of the group potentially being screened are; and a myriad of other factors.
As we should all know: Math is Hard!