“Density Alone Not a Risk Factor” was a headline in media from a talk by Croatian researchers at RSNA 2015. This is one such story: Breast Density Alone Not Strong Risk Factor for Cancer.
The researchers collected visual BI-RADS 4th Edition readings for cancer cases and controls, and found no significant difference in breast density. This obviously contradicts many other papers, including the one from Mayo in Radiology 2016 based on a far bigger data set.
How could this be? The answer lies in the population – vast numbers of women had fatty breasts (83% in the cases, 89% of controls), and 70% of women were reportedly obese. So, very few women actually had dense breasts (~7 women had extremely dense breast) meaning that study was pretty under-powered. The study needs more cases, needs to collect and correct for BMI, and also needs to include interval and screen detected cancers.