Breast MRI in Women with Dense Breast Tissue

Women with dense breast tissue (density 3-4) are at an increased risk of developing breast cancer. This accounts for approximately 40% of women aged 40-70.

How often do we miss breast cancer in this category during mammography? - Up to 40%.

Dutch scientists (Bakkler et al. 2019) decided to conduct an experiment to determine how many more carcinomas would be detected by adding contrast-enhanced breast MRI to the standard mammography, which did not reveal any abnormalities.

Results:

• Half as many interval carcinomas (those detected between two screening examinations).
• 16.5 carcinomas were detected per 1000 MRI examinations (compared to 7 per 1000 with standard mammography).

Excellent results, isn't it? Now let's think and ponder. Is there any benefit in detecting additional (16.5-7=9.5) carcinomas? It seems like an obvious answer – we are finding twice as many carcinomas. How could this be a bad thing?

But it's not all so straightforward.

Yes, indeed, we are finding more carcinomas, but with MRI screening, more biopsies are performed because MRI is a low-specificity examination – 74% of biopsies turned out to be false negatives. In other words, we see an abnormality on MRI, interpret it as suspicious for cancer, perform a biopsy, and... it turns out to be a benign change or simply active breast tissue. So, did we unnecessarily worry the woman and subject her to an unnecessary biopsy? Could the biopsy have been avoided? Perhaps, but then how do we answer the question – is this cancer or a benign finding? One option is observation. But imagine a woman who knows she has a breast change that requires monitoring because the probability of cancer is 25%. Furthermore, 72 out of 79 carcinomas detected in this study using MRI were found at an early stage. It is unclear whether our early detection will benefit the patient in the long term (prolong life) or cause stress and high psychological risk.