Avoiding preoperative breast MRI when conventional imaging is sufficient to stage patients eligible for breast conserving therapy

Abstract

Aim

To determine when preoperative breast MRI will not be more informative than available breast imaging and can be omitted in patients eligible for breast conserving therapy (BCT).

Methods

We performed an MRI in 685 consecutive patients with 692 invasive breast tumors and eligible for BCT based on conventional imaging and clinical examination. We explored associations between patient, tumor, and conventional imaging characteristics and similarity with MRI findings. Receiver operating characteristic (ROC) analysis was employed to compute the area under the curve (AUC).

Results

MRI and conventional breast imaging were similar in 585 of the 692 tumors (85%). At univariate analysis, age (p < 0.001), negative preoperative lymph node status (p = 0.011), comparable tumor diameter at mammography and at ultrasound (p = 0.001), negative HER2 status (p = 0.044), and absence of invasive lobular cancer (p = 0.005) were significantly associated with this similarity. At multivariate analysis, these factors, except HER2 status, retained significant associations. The AUC was 0.68.

Conclusions

It is feasible to identify a subgroup of patients prior to preoperative breast MRI, who will most likely show similar results on conventional imaging as on MRI. These findings enable formulation of a practical consensus guideline to determine in which patients a preoperative breast MRI can be omitted.

Introduction

There is a persisting controversy about the role of contrast-enhanced magnetic resonance imaging (MRI) of the breast in patients with known breast cancer and eligible for breast conserving therapy (BCT). BCT includes limited surgery to excise the tumor and postoperative radiotherapy. Several studies demonstrated that MRI has superior sensitivity to detect invasive breast cancer compared to conventional imaging (mammography and ultrasound) and clinical breast examination (CBE) [1], [2], [3], [4]. This sensitivity leads to improved definition of tumor extent [4], [5]. As a result, MRI has been expected to increase complete resection rates, breast cancer control and cosmetic outcome, but these effects have not been demonstrated consistently.

Opponents of the routine use of preoperative breast MRI point at the risk of overdiagnosis and overtreatment, increase in cost, delay in surgery, increased patient anxiety, and the ability of adjuvant therapy to eradicate possible additional disease foci [2], [6]. Conversely, it has been postulated that if lumpectomy margins need to be clear from microscopic disease in order to reduce the risk of local recurrence, small foci detected on MRI also need identification and excision [7].

The use of MRI in the preoperative staging of BCT is recommended by a number of studies [8], [9], but remains controversial in others [2], [6]. Meanwhile, preoperative breast MRI is increasingly used, and the need for clinical guidelines rises.

Parallel to the efforts to define the role of preoperative MRI in the ipsilateral breast, both the European Society of Breast Imaging, and the American College of Radiology (ACR) have recommended the use of MRI to screen the contralateral breast in patients with proven cancer [9], [10]. More recently the European Society of Breast Cancer Specialists (EUSOMA) has published general recommendations for the application of breast MRI [11]. The authors acknowledged that preoperative MRI may have potential advantages for particular subgroups (e.g., patients with invasive lobular cancer and women at high risk for breast cancer), but recommended further research.

There is similarity between conventional imaging and MRI in approximately 85% of BCT patients [12], [13], [14]. So regardless which guidelines are used for preoperative breast MRI, the value of this technique can be disputed in this group of patients. If this group could be identified prior to the decision to perform the MRI, studies on MRI-detected additional disease could be powered more efficiently while reducing the number of clinical procedures and cost.

Our aim was to investigate clinical, pathological and imaging characteristics available prior to MRI to identify patients who are expected to have MRI findings similar to conventional imaging findings. Combined with existing knowledge on preoperative breast MRI we formulated practical guidelines to determine in which patients a preoperative breast MRI can be omitted.