Yes there have been women diagnosed with breast cancer which was not seen on mammograms but that is a small number. Advocates for this law want to help women be in more control of their healthcare. Advocates against it are concerned about overdiagnosis and additional costs - particularly in states where insurance companies are required to pay for ultrasounds after clean mammograms.
And doctors have said they don't have the tools to do much with the information.
"New ways of classifying dense breast tissue could put even more women in the category of receiving dense breast notifications, said Dr. Priscilla Slanetz, who recently wrote a New England Journal of Medicine article questioning the effectiveness of dense breast notification laws.
One reason she wrote the article, she said, was "in our state [Massachusetts] very few of our primary care providers have any knowledge about breast density and strengths and limitations of these different tests" for supplemental screening.
The same may hold true in California, where a small survey of primary care doctors found that only half of them had heard of the state's 2013 dense breast notification law and many felt they didn't have enough education to address what breast density meant for their patients.
On this point, both supporters and critics of the laws agree: doctors need better tools to help their patients identify their individual cancer risks."
Okay, so now we have people who want to have these laws but we do not have a way to deal with the information. How helpful.