MRI for Breast Cancer Screening

Numerous studies have shown the superiority of contrast-enhanced MRI to current methods. Abbreviated protocols make MRI feasible for screening.

The current screening methods do not detect all breast cancers. They might miss the development of faster growing cancers, leading to a high rate of interval cancers, or mammography might not be sensitive enough in high-dense breasts. Christiane Kuhl, RWTH Aachen, Germany, showed convincing results for an alternative method: MRI.

MRI detects more biologically important cancers than any other modality

Digital breast tomosynthesis (DBT) and ultrasound have been proposed as (additional) screening modalities. However, the additional cancer yield by adding DBT to mammography varies between 1.1 and 2.7 cases per 1000. Using additional ultrasound increases cancer yield between 1.7 to 4.6 cases per 1000. In contrast, screening by MRI alone yields in a mean of 14.6 additionally detected cancers per 1000. Kuhl’s own study, published in 2017, showed an improved detection of breast cancer and prognostic relevant breast cancer in women with average risk of developing breast cancer at a rate of 15.5 per 1000 (Kuhl C et al. 2017).
Additionally, the interval cancer rate was nil. Kuhl therefore promoted MRI as a single screening tool.

The Aachen abbreviated MRI protocol

At Kuhl’s institution, breast MRI examinations are performed at 1.5 T with axial bilateral imaging, no fat saturation and a 2D multi-slice gradient echo (GRE). The protocol takes only three minutes instead of 15 for the full-length protocol.

Kuhl showed that the first (one-minute) post-contrast subtracted image delivers a better lesion enhancement compared to later captured images. These are processed to maximum intensity projection images (MIP) that are used to detect and characterize significant lesion enhancement. Kuhl showed several examples. “The reading time for MIP images is approximately 2.8 seconds,” she said. It takes ten times more to read individual subtracted images, and even much longer – up to 20 minutes – to read mammography or ultrasound images. Moreover, the abbreviated MRI protocol is not inferior to the full MRI protocol.

Conclusion and Discussion

Kuhl provided evidence from multiple studies that show the superiority of MRI for breast cancer detection to mammography, DBT and ultrasound. She developed an abbreviated, three-minute MRI protocol that would make MRI suitable for screening.

“I do not recommend MRI as a screening methods for everybody,” she said, when somebody from the audience pointed out that adding ultrasound to mammography is sufficient in many cases. “I advocate for a personalized risk stratification. There are women who will not need any screening, and there are women who definitely need MRI as a screening tool.”

Somebody else asked whether Kuhl would promote pre-operative MRI for all patients. “Definitely yes,” Kuhl answered. “We do pre-operative MRI for much lesser reasons.” - The chair of the session, Julia Camps Herrero, asked why pre-operative MRI is still not part of the current guideline. “This is unconceivable,” Kuhl answered. “The evidence is solid. Prostate MRI has less convincing study results and can be found in the guidelines.”

Asked about the use of gadolinium-based contrast agents and the problem of gadolinium retention, Kuhl answered: “There are no known clinical effects. I think that the published papers on the matter get too much attention. We need more people to balance things out.”

Sources

Kuhl CK et al. Supplemental Breast MR Imaging Screening of Women with Average Risk of Breast Cancer. Radiology. 2017;283(2):361-70.