Breast vascular mapping obtained with contrast-enhanced MR imaging: implications for cancer diagnosis, treatment, and risk stratification.

The value of breast vascular maps obtained using contrast-enhanced MR imaging has recently been explored. Additional information is obtained only by evaluating maximum intensity projections of the first dynamic subtraction to achieve a form of MR angiography of the breast. No increase in acquisition time and no dedicated contrast injections are needed. Four studies have been performed to evaluate the one-sided (asymmetric) increase in vascularity associated with ipsilateral cancer in a total of 404 patients with a cancer prevalence ranging from 38% to 80%. Sensitivity ranged from 72% to 88%, specificity from 57% to 100%, positive predictive value from 85% to 100%, negative predictive value from 38% to 88%, and overall accuracy from 73% to 87%. An asymmetric increase in breast vascularity ipsilateral to a cancer may be due to reduced flow resistance in the tumour, to a high metabolic rate (more likely in large tumours) or to angiogenic stimulation of the whole breast harbouring the lesion (more likely in small tumours). Tumour size could play a specific role in determining the ipsilaterally increased vascularity, and invasive cancers might be more frequently associated with ipsilaterally increased vascularity than in situ cancers. Moreover, while a reduction in breast vasculature has anecdotically been observed in breasts with locally advanced cancers treated with neoadjuvant chemotherapy, especially when taxanes are used, the higher incidence of breast cancer in patients with size asymmetry between the breasts as determined on screening mammography suggests that a role for breast MR vascular mapping in breast cancer risk stratification should be explored. Finally, arteries and veins might be differentiated with dedicated techniques. High-relaxivity agents may be used with advantage in these future investigations.