Breast disease is a novel clinical application for magnetic resonance imaging (MRI). Although data do not support routine use during breast cancer evaluation, evidence suggests that this technology is being rapidly adopted. The goal of this study was to gain a better understanding of breast MRI practice patterns on a population level.

A retrospective cohort was constructed using a commercial database of administrative claims from 126 unique insurance carriers. Women aged 18-64 who were continuously enrolled and had an incident breast cancer diagnosis from 2005-2007 were included. Inpatient and outpatient imaging and surgical procedures were captured for each patient.

The mean age at diagnosis was 52.1 years (range 20-64). Overall, 30.5% (n=6,230) of 20,440 identified incident breast cancer patients underwent breast MRI. Younger women were more likely than older women to receive MRI. MRI use increased from 24.6% of those diagnosed in 2005 to 39.0% of those diagnosed in 2007. Seventeen percent of women in the MRI group had more than one MRI (n=1,062). MRI was more common in women who underwent mastectomy (n=7,535) compared to those who underwent breast conservation therapy (n=11,736) (36.0% vs. 27.7%, p<0.05). Mean state-level utilization was 30.4%. For states in which there were >100 cases, utilization ranged from 9.7% to 63.7%.

Utilization of breast MRI in this privately insured population is significant and increasing. In this study we found large differences in breast MRI utilization by state. Uncertainty surrounding the utility of breast MRI in the general population may contribute to unexplained regional variation.