The use of MRI for breast cancer screening and to guide treatment decisions is increasing, despite little evidence of its benefit, according to the first paper in The Lancet Series on breast cancer. The findings show that although MRI is a valuable tool for screening women at genetically high risk of breast cancer, there is limited evidence to support its use in screening women in the general population, or that its routine use before breast-conserving surgery improves patient selection, reduces surgical procedures, or lowers the risk of local (confined to the breast) cancer recurrences.
MRI has, over recent years, been widely adopted into clinical practice based on the assumption that its increased sensitivity at detecting cancer will improve outcomes for patients. In this paper, Monica Morrow from Memorial Sloan-Kettering Cancer Center, New York, USA, and colleagues review research from the past decade to examine that belief.
There is sufficient evidence that MRI is a beneficial screening tool in women at high risk of breast cancer (because of their family history or known gene mutation), and can accurately identify tumours missed by mammography and ultrasound. However, little is known about whether or not this improved detection has an impact on survival.
According to the authors, there is no evidence that this increased sensitivity translates into better surgical treatment or prognosis when used to evaluate women prior to surgery: "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."
Furthermore, the impact of MRI on longer-term outcomes such as the incidence of contralateral (in the other breast) cancer or the recurrence of ipsilateral (in the affected breast) cancer cannot be established because of the limited number of trials, many of which are of low quality.
Research suggests that MRI is more reliable than traditional examinations (physical examination, mammography, and ultrasonography) at assessing the extent of residual disease after, and response to, preoperative chemotherapy. But whether this results in an improved ability to select patients suitable for breast-conserving therapy is unclear.
"Ultimately, the true value of MRI might lie in its ability to predict biological behaviour, 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", conclude the authors.
Professor Monica Morrow, Memorial Sloan-Kettering Cancer Center, New York, USA. Via Memorial Sloan-Kettering Cancer Center Press Office T) +1 212 639 3573 E) morrowm@mskcc.org
Journal
The Lancet