Women who are at high risk of developing breast cancer or experiencing a recurrence should be screened twice a year using MRIs rather than the standard protocol of once-a-year mammograms, says a team of researchers from the US and Brazil.

Their study, now published in Clinical Cancer Research, involved performing both tumor imaging protocols on 295 women for an average of four years and comparing how well the techniques fared at detecting any malignancies that developed.

"This study demonstrates for the first time that aggressive breast cancers can be caught early, without excessive recalls or biopsies," researcher leader Dr Olufunmilayo Olopade, Associate Dean for Global Health at the University of Chicago Medical Center, said in a statement.

The research was undertaken with the goal of finding a better way to monitor women with genetic variations known to greatly increase the likelihood of aggressive breast cancers, such as mutations in the BRCA1 and BRCA2 genes.

"Women with mutations in BRCA1 or BRCA2 have very different needs for surveillance for breast disease than women with no mutations in these genes,” added co-author Mary-Claire King, of the University of Washington. “This is particularly true for healthy young women with mutations.”

Their trial enrolled 157 women who carried any of 11 known breast cancer-related genetic abnormalities; 75 of these had BRCA1, 61 had BRCA2. Another 138 women who had been diagnosed with either breast cancer or ductal carcinoma in situ (DCIS) – a non-invasive cancer of the milk ducts that can progress to an aggressive form – before the age of 35 were included. All were recruited from a single center between 2004 and 2016 and were followed for at least one year.

Each participant underwent bi-annual MRI with a clinical breast examination and an annual mammogram. If suspicious signs appeared on any type of image, a biopsy was ordered.

During the study period, 17 instances of cancer were found: 13 were early stage breast cancer and 4 were DCIS. Fifteen tumors were in subjects with genetic variants (11 BRCA1, 3 BRCA2, 1 CDH1). In all cases, the malignancy had not spread to lymph nodes and was less than a centimeter in diameter. Happily, all 17 are currently alive and free of systemic cancer.

"This is the ultimate goal of breast cancer screening," said author Gregory Karczmar, a professor of radiology at the University of Chicago. "Detecting node-negative, invasive tumors less than 1 centimeter."

After analyzing how each scan played into these diagnoses, the researchers calculated that the sensitivity of bi-annual MRI screening alone was 88.2 percent; meaning that this protocol was able to catch 88.2 percent of cancer cases. Annual mammograms alone fared much worse, with only 41.2 percent sensitivity. Because the sensitivity of the two protocols combined was not significantly better than MRI alone, the team concludes that mammograms could be discarded completely for high-risk women. (Karczmar notes that mammograms are unsuitable for about 40 percent of all women if you also factor in the proportion with dense breast tissue.)

Unfortunately, as of now, MRIs are too expensive for routine screenings of all women, yet the authors hope these findings will encourage health care providers – and insurance companies – that using the technology to closely monitor the high-risk subgroup of women is worth the cost. Moreover, they note that improvements in the technology have already begun to make MRI cheaper, a trend that is sure to continue.

The American Cancer Society (ACS) currently recommends an annual MRI and annual mammogram for high-risk women, typically starting at age 30.