You know, most of the rest of the world follow “screen over 50, every two years” guideline already (or so I’ve been told) so I suspect some of this is “everyone else does it this way.”
Also - I’m assuming they’re referring to screening the general population. Women at known high risk might well still be considered for earlier screening. Women with many relatives with breast cancer, history of early breast cancer in the family, or with known breast cancer gene susceptibility.
On the other hand, there are women such as myself where there are NO blood relatives with breast cancer on either side of the family and an overall very low risk of cancer (I’ve had two relatives with cancer, one of which has been in remission for over 50 years). Frankly, I am MUCH more worried about my risk of heart disease, which runs rampant in my family. Yes, yes, I realize that I could be the first to get breast cancer and I did get a baseline - in my 40’s. I keep an eye on the girls, but honestly, like I said, it’s heart disease I’m most concerned about.
As always, your mileage may vary - and probably will based on family and personal history.
On the end point - my mother ceased to be screened for breast cancer before 74. Why? Because heart disease had so debilitated her that there was no way in hell she could survive even one round of chemo or radiation, in fact, it was unlikely she’d survive any form of surgery, either. So why bother? If the treatment would kill her faster than the cancer (and it would have) there’s no point to screening. If she had been found to have cancer the only treatment possible would have been palliative care anyway, and that could have waited until she was more overtly symptomatic. As it happens, she died without ever developing cancer. It was the heart disease that got her - like I said, it runs rampant in my family.
So really, it makes sense that SOME women should be screened very early, in their 30’s, while for others the risk is so much lower that waiting until 50 is probably not unreasonable. And if the woman is so debilitated by other condition(s) that it wouldn’t be possible to treat breast cancer if it was found there really is no use for screening before actual symptoms. To my mind the biggest problem is slapping a blanket recommendation on everyone without regards to a personal risk assessment and considering the patient as a whole.