MRIs may not be a helpful breast cancer screening tool for all women, a new review suggests.

Doctors have increasingly turned to MRI based on the assumption that it leads to better detection of tumours. Researchers considered MRI a valuable tool for screening women at genetically high risk of breast cancer. Jean-Paul Pelissier/Reuters

To put that assumption to the test, Prof. Monica Morrow from Memorial Sloan-Kettering Cancer Center in New York and her colleagues reviewed studies published on the topic over the past 10 years.

In this week's issue of the medical journal the Lancet, they concluded that MRI is a valuable tool for screening women at genetically high risk of breast cancer because it accurately identified tumours that were missed by mammography and ultrasound, but not other women.

"The only groups for which sufficient evidence to justify the use of MRI screening was felt to be present were women proven to be BRCA mutation carriers, untested first-degree relatives of mutation carriers, and women with a lifetime risk of breast cancer development of 20 per cent or more as determined by models based on a family history of breast cancer."

There was limited evidence to support its use in screening women in the general population, they said.

It is also not known whether that improved detection rate actually improves survival of breast cancer patients, the researchers said.

In the future, the true value of MRI might lie in its ability to predict biological behaviour, they concluded. If further studies show MRI succeeds at detecting early changes in the metabolism of cells, the tool might help predict how tumours respond to treatment to guide decisions about chemotherapy.

A second review paper appearing in the same issue of the Lancet concluded that genetic profiling of breast cancer has improved understanding of the disease.

But its value in terms of guiding choices for the treatment of individual patients was limited, according to the 10-year review.