Breast Cancer - MRI Does Not Help, Even Though Usage Grows

MRI (magnetic resonance imaging) is increasingly used to help doctors decide on treatment options for breast cancer patients, despite there being very little evidence that this type of imaging has any benefit, researchers from the Memorial Sloan-Kettering Cancer Center in New York, USA, reported in The Lancet series of articles.

Over recent years the use of MRI scans has been widely adopted by clinical practices, because of the assumption that its increased sensitivity at identifying cancer will improve patients' outcomes. Monica Morrow and team set out to determine whether this assumption was valid. They researched peer-reviewed published articles over the last decade.

They discovered that although MRI proves to be a valuable tool for screening women with a genetically high risk of breast cancer, the evidence for screening those in the general population is limited. They also found limited evidence to support that routine MRI screening before breast-conserving surgery improves patient selection, lowers the risk of local breast cancer recurrences, or reduces surgical procedures.

The team noted that sufficient evidence exists for MRI to be a beneficial screening tool in women with a genetically high risk of breast cancer, due to family history or known gene mutation, and that it can accurately detect tumors that have been overlooked by mammography and ultrasound, although nobody really knows whether this improved detection has an impact on survival or not.

The researchers say that there is no evidence that the increased sensitivity of using MRI scans to examine women before surgery results in better surgical treatment or prognosis.

The authors comment:

"The available data...do not support the idea that MRI improves patient selection for breast-conserving surgery or that it increases the likelihood of obtaining negative margins [no cancer cells found in margins of resection] at the initial surgical excision."

They add that in addition, the impact of MRI on longer-term outcomes cannot be determined due to the limited number of trials and the poor quality in many of these human studies. Long-term outcomes include the incidence of cancer affecting the other breast (contra lateral cancer) or recurrence in the affected breast (ipsilateral cancer).

According to the researchers, MRI screening proves to be more reliable at evaluating the extent of residual disease after, and in response to preoperative chemotherapy compared with traditional examinations, such as physical examination, mammography, and ultrasonography. However, it is unclear whether this results in an improved ability to select suitable patients for breast-conserving therapy.

In an Abstract in the journal, the authors concluded:

"Ultimately, the true value of MRI might lie in its ability to predict biological behavior, rather than to quantitate low-volume disease. Very early changes in intracellular metabolism that are detectable by magnetic resonance spectroscopy seem to be predictive of response to treatment, and if validated in larger studies could avoid the toxicity and expense of continuing a chemotherapy regimen that will not be beneficial."