Breast MRI in nonpalpable breast lesions: a randomized trial with diagnostic and therapeutic outcome – MONET – study

The MONET – study (MR mammography Of Nonpalpable BrEast Tumors) is a randomized controlled trial with diagnostic and therapeutic endpoints. We aim to include 500 patients with nonpalpable suspicious breast lesions who are referred for biopsy. With this number of patients, the expected 12% reduction in surgical procedures due to more accurate preoperative staging with Breast MRI can be detected with a high power (90%). The secondary outcome is the positive and negative predictive value of contrast enhanced Breast MRI. If the predictive values are deemed sufficiently close to those for large core biopsy then the latter, invasive, procedure could possibly be avoided in some women. The rationale, study design and the baseline characteristics of the first 100 included patients are described.Study protocol number NCT00302120Breast cancer is the most frequently occurring malignant disease in women with a lifetime risk of 1 in every 8 – 9 women [1]. Like many other Western countries, the Netherlands launched a screening program for breast cancer and since 1998, all women between 50 and 75 years of age are offered biannual mammographic examination. This program reveals approximately 4000 suspicious, nonpalpable breast lesions each year in the Netherlands [2]. In clinical practice, another 3000 nonpalpable lesions are detected annually in women with a high genetic risk or a history of breast cancer [3]. Of all suspicious nonpalpable breast lesions, 10–55% of lesions turn out to be malignant (ductal carcinoma in situ or invasive carcinoma) after large core needle biopsy (LCNB) depending on the aggressiveness of the referral of patients which varies across countries [4]. Subsequently, these patients are scheduled for surgical removal of the malignant breast tumor. In a relatively high proportion of these patients (approximately 20–30%), several surgical procedures (re-excisions or conversions from lumpectomy towards mastectomy) are needed to achieve complete removal of the prim