> you'd physically examine yourself looking for lumps on a monthly basis.
That's not the current advice. Current advice is that women become aware of what's normal for their breasts, and look for certain specific changes and not the vaguely described "lumps".
http://www.nhs.uk/chq/pages/1740.aspx?CategoryID=60&SubCateg...
> and yet when something more accurate and objective is available
Is it more accurate? Mammograms are sensitive, but have a high false positive rate, especially for younger women.
(All the sites I can find report sensitivity and false positive rates as percentages, which is a terrible way to report this information.)
https://ww5.komen.org/BreastCancer/AccuracyofMammograms.html
> Overall, the sensitivity of mammography is about 84 percent [9]. This means mammography correctly identifies about 84 percent of women who truly have breast cancer.
> The more mammograms a woman has, the more likely she will have a false positive result that will require follow-up tests. The chance of having a false positive result after 10 yearly mammograms is about 50-60 percent [22-24].
http://www.breastcancer.org/symptoms/understand_bc/statistic...
> In 2017, an estimated 255,180 new cases of invasive breast cancer are expected to be diagnosed in women in the U.S., along with 63,410 new cases of non-invasive (in situ) breast cancer.
Ann, a 45 year old woman, goes for a mammogram. It returns a positive result. What are the chances that Ann has breast cancer? (Scarily lots of doctors can't answer this question if the information is presented as percentages. See Gerd Gigerenzer's book Reckoning with risk for many examples.)
https://www.cancer.gov/types/breast/hp/breast-screening-pdq
> Magnitude of Effect: In the randomized controlled trials (RCTs), for women aged 40 to 74 years, screening with mammography has been associated with a 15% to 20% relative reduction in mortality from breast cancer.[1] Absolute mortality benefit for women screened annually for 10 years is approximately 1% overall, ranging from 4 per 10,000 women who start screening at age 40 years to 50 per 10,000 women who start at age 50 years.[2] Based on the 25-year follow-up from the Canadian National Breast Screening Study (CNBSS), an RCT of breast cancer screening,[3] there is some uncertainty about the magnitude of benefit of mammography in the present day.