MRI Wins Again In Women At High-Risk For Breast Cancer

MRI-based screening detected cancers at an earlier stage than mammography in women with a familial risk of breast cancer, according to the Dutch FaMRIsc trial.

In a cohort of 1,355 women with a familial predisposition to breast cancer who were randomized to MRI (n=675) or mammography (680), MRI detected 40 cancers versus 15 with mammography (P=0.0017), reported Madeleine M.A. Tilanus-Linthorst, MD, of Erasmus University Medical Center, in Rotterdam, the Netherlands, and colleagues.

Furthermore, the 24 invasive cancers in the MRI-detected group were smaller than the eight found in the mammography group (median size 9 mm vs 17 mm, P=0.010). They were also less frequently node-positive: four (17%) of 24 compared with five (63%) of eight (P=0.023), they reported in Lancet Oncology.

Additionally, tumor stages in the MRI group were significantly earlier with 12 (48%) of 25 tumors identified as T1a and T1b compared with one (7%) of 15 in the mammography group. One (4%) of 25 in the MRI group and two (13%) of 15 in the mammography group were stage T2 or higher (P=0.035).

“We conclude that in real-life practice, MRI screening can result in an important and favourable shift in tumour stage at time of breast cancer detection compared with mammography screening, reducing the incidence of late-stage cancers and thus reducing the need for adjuvant chemotherapy and the risk of mortality,” Tilanus-Linthorst’s group wrote.

However, they conceded that the advantages of MRI screening might come at the cost of overdiagnosis, with more false-positives, especially in women with high breast density. A 2018 study reported higher biopsy rates and lower yields with MRI screening versus mammography in women with and without a personal history of breast cancer.

The FaMRIsc trial recruited women, ages 30 to 55, at 12 Dutch hospitals from 2011 to 2017. Eligible participants had a cumulative lifetime breast cancer risk of at least 20% owing to familial predisposition but no documented genetic mutations in BRCA1, BRCA2, and TP53. About 15% of all breast cancers occurred in women with a family history of the disease but no causative hereditary genetic mutation, the authors noted.

The women received annual MRI with a clinical breast exam or annual mammography plus clinical exam. The mean number of screening rounds per woman was 4.3. Participants who were breastfeeding, pregnant, previously screened for breast cancer, or diagnosed with ductal carcinoma in situ were eligible, but those previously diagnosed with invasive carcinoma were excluded.

All seven tumors classified as stage ≥T2 occurred in the two highest breast density categories (C and D, P=0.0077). “High breast density was indicative of a poorer tumour stage and lower specificity both in the MRI and mammography groups and was more informative than age to predict screening performance,” the authors wrote.

There was one death from breast cancer in the mammography group. The highest cancer incidence in the mammography group fell in the second year, with an almost equally steep decline in cancer incidence in both groups after that, suggesting that the effect of previous screening on the complete study was limited.

A study limitation was the small number of detected cancers when stratified according to density or age because the study was powered to show a difference in tumor size between the two screening groups. Hence, unlike earlier research, it did not see a significant decrease in sensitivity with increasing breast density.

Another limitation was that previous screening might have affected cancer incidence, and possibly more in the mammography group since previous mammography screening was more common in the study population.

The authors acknowledged that better specificity might be achievable if MRIs are done in expert clinics. “Further improvements might come from abbreviated and, for specificity, artificial intelligence based assistance,” they wrote.

In an accompanying comment, Christiane K. Kuhl, MD, of University Hospital Aachen in Germany, called the results “compelling.” She noted that in line with previous research, breast cancer detection almost tripled in the MRI group. In her view, the study also “provides important outcome measures useful to evaluate the oncological implications of the respective screening methods.”

But Kuhl cautioned that the follow-up time was too short to assess the impact of each screening method on breast cancer mortality, adding that mortality analyses will be possible a decade from now.

As for the problem of false positives, “In view of the devastating consequences of a late diagnosis of cancer, avoiding underdiagnosis should be deemed more important than avoiding overdiagnosis,” she stated. “We can alleviate much of the adverse consequences of overdiagnosis by providing patient information and appropriate selection of management.” – Medpage Today