DOI: 10.1097/gme.0b013e31824af478

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PMID: 22453132

Issn Print: 1072-3714

Publication Date: 2012/04/01


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Aromatase inhibition to decrease background parenchymal enhancement: premedication before magnetic resonance imaging?

Julliette M. Buckley; Kevin S. Hughes

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Excerpt

Magnetic resonance imaging (MRI) of the breast is a useful tool in diagnosing mammographically occult cancers and can provide, in selected circumstances, additional diagnostic information on women with newly diagnosed breast cancer. At least one prospective trial supports the use of breast MRI as an adjunct to mammography in screening women at high risk of breast cancer, although no survival data are available as of yet.1 Although the sensitivity of breast MRI approaches 90%, the specificity remains low, with quoted percentages of 37% to 98%.2 Nonspecific enhancement of normal breast parenchyma can lead to a high rate of call backs for additional diagnostic tests and an increased biopsy rate in many women. Patients considered “high risk” and therefore most likely to benefit from MRI, despite a high risk of a false-positive result, have been defined by the American Cancer Society guidelines for MRI screening, which limit screening MRI to women with a known BRCA mutation, first-degree relatives of BRCA mutation carriers, and women with a lifetime risk of breast cancer higher than 20% to 25% as estimated by risk assessment models, such as the BRCAPRO, a statistical model and software which predicts the genetic predisposition to breast and ovarian cancer. Rather than use the risk models to estimate lifetime risk, we prefer genetic testing for BRCA mutations in high-risk women (those with a >10% risk of carrying a mutation). Murphy et al,3 in the analysis of the BRCA PRO results of 18,190 women undergoing screening mammography, found that a significant number of women who were predicted mutation carriers would not meet the American Cancer Society criterion of greater than 20% lifetime risk and thus would not be offered breast MRI.3 To comprehensively identify the MRI target population, genetic testing should be encouraged in all women identified as high risk, and MRI should be considered in those who test positive or indeterminate.
In the current issue of Menopause, Mousa et al4 attempt to address the issue of the high rate of false positives associated with MRI. The authors present a novel approach aimed to increase the specificity of breast MRI by pretreating a cohort of women with the aromatase inhibitor (AI) letrozole to decrease background parenchymal enhancement.
Previous studies have demonstrated the effects of physiologic hormonal status,5 hormone therapy,6 and selective estrogen receptor modulators7 on the background enhancement on breast MRI. AIs block estrogen synthesis in peripheral tissues, which is the primary source of estrogen in postmenopausal women and have become the treatment of choice for postmenopausal patients with endocrine-sensitive breast cancer, resulting in significantly improved disease-free survival.8
The only other study examining the effects of AIs on MRI breast parenchymal enhancement to date has been a retrospective review of pretreatment and posttreatment breast MRIs of 168 women taking AIs for breast cancer by Goldfarb et al,9 presented in poster form at the 2011 San Antonio Breast Cancer Symposium. The authors found that adjuvant AIs were associated with a significant decrease in breast parenchymal enhancement on MRI. The current study examines the effect of a short course of high-dose letrozole on breast parenchymal enhancement in postmenopausal women. The dose of letrozole was arbitrarily chosen and is significantly higher than that used in current clinical practice, although well below the maximum tolerated dose. The 3-day duration of treatment seemed to be well tolerated, with no serious events noted, although concurrent use of hormone therapy (HT) by 12 of the 14 study participants may have lowered the incidence and severity of the adverse effects reported. It is acknowledged by the authors that future studies including women not taking HT would be of value.

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