Clinical utility of breast magnetic resonance imaging in patients presenting with primary breast cancer

Abstract

Since magnetic resonance imaging (MRI) of the breast has been shown to be sensitive in identifying the extent of the primary tumor and other foci of cancer, we examined its clinical utility in the surgical management of breast cancer patients. From January 2004 to April 2007, 117 patients with newly diagnosed breast cancer underwent bilateral MRI prior to definitive surgical management. Additional lesions were found in 27 patients (23.1%) in the ipsilateral breast and 19 patients (16.2%) in the contralateral breast. Twelve patients (10.3%) had more than one new lesion identified. Six patients (5.1%) had a larger area of tumor than detected by mammography or ultrasound. Additional biopsies were performed in 27 patients (23.1%). Additional foci of cancer were identified in 17 patients (14.5%): 12 (10.2%) in the ipsilateral breast and 5 (4.3%) in the contralateral breast. This information changed the clinical management in 23 cases (19.7%). Further studies are needed to confirm the benefits of MRI relative to its costs and to further identify the appropriate patients to undergo this imaging procedure.

Patients presenting with breast cancer often have the choice between breast-conserving therapy and mastectomy. A critical factor in counseling these patients is an understanding of the full extent of the primary cancer. It has long been understood that some breast cancer is mammographically occult, particularly in women with dense breast tissue. Invasive lobular cancer is often occult or underestimated by conventional imaging alone.

Magnetic resonance imaging (MRI) of the breast has been shown to be more sensitive in detecting breast cancer than mammography or breast ultrasound. In studies comparing MRI with mammography, the sensitivity of MRI in detecting breast cancer was 77% to 100%, while that of mammography has been reported as 63% to 98% and as low as 30% to 48% in dense breasts (1–5). The American Cancer Society recently published recommendations for the use of MRI in the screening of patients at high risk of breast cancer (6). High-risk patients include those with a familial risk of cancer of 20% or more, a history of chest irradiation at a young age, or a BRCA mutation or certain other genetic mutations in the patient or first-degree family members. MRI is recommended annually in addition to mammography for these patients.

In clinical practice, MRI is utilized in patients presenting with breast cancer to help determine the type and extent of surgery that is appropriate. If a larger, more extensive primary tumor or another focus of breast cancer is found, that information often influences treatment decisions. Criticisms of MRI include its lack of specificity and the need for MRI-guided biopsies of certain abnormalities. This paper reviews the experience of breast MRI in patients presenting with primary breast cancer and the technique's utility in the surgical management of these patients.

MATERIALS AND METHODS

An institutional review board–approved review of a prospective breast cancer database was performed. Patients were treated at a single breast practice by two surgeons from January 2004 through April 2007. Inclusion criteria were patients with newly diagnosed invasive breast cancer or ductal carcinoma in situ who underwent a bilateral MRI prior to definitive surgical management. Patients were excluded if they had an MRI for follow-up of breast cancer, had a screening MRI, or had an MRI for benign conditions.

MRIs were performed with a dedicated breast MRI unit with intravenous gadolinium contrast infusion. All studies were interpreted by radiologists experienced in breast MRI. In general, suspicious MRI findings not previously identified by mammography or ultrasound were evaluated with a focused ultrasound in an attempt to retrospectively identify the MRI abnormality. If the abnormality was identified by ultrasound, an ultrasound-guided core needle biopsy was performed. If the lesion was not identified by ultrasound, then an MRI-guided core biopsy was performed.

Reviewed data included the indication for MRI and the number of suspicious MRI abnormalities in the ipsilateral breast (including the index lesion) and the contralateral breast. Abnormal findings detected by MRI were defined as any abnormalities outside of the known cancerous lesion in the ipsilateral breast or any abnormality in the contralateral breast. These lesions were then biopsied if warranted by the clinical situation. Data were collected on the number of ultrasound-guided or MRI-guided needle biopsies obtained as a result of MRI findings. Each case was reviewed to evaluate the MRI findings' impact on the management of the patient, categorized as one of the following: no change in management, the addition of another area within the lumpectomy, ipsilateral mastectomy as a result of the MRI findings, or contralateral mastectomy as a result of the MRI findings. Additional information examined included patient demographics, tumor profile and staging, and surgery performed. Although survival data were part of the database, no attempt was made to correlate the use of MRI with disease-free or overall survival.

RESULTS

From January 2004 through April 2007, 117 patients presenting with breast cancer underwent bilateral breast MRI. All patients were women, with a mean age of 55 years (range, 23–84). Indications for MRI are listed in Table 1. The presenting cancer was identified in all cases on the MRI. The histologic findings for the primary lesion are presented in Table 2. Additional suspicious lesions were identified in the ipsilateral breast in 27 patients (23.1%), while 19 patients (16.2%) were found to have a suspicious focus in the contralateral breast. Forty-six new suspicious foci were identified in the entire cohort of patients. The mean number of suspicious lesions in the ipsilateral breast including the index cancer was 1.4 (range, 0–7), while the mean number of suspicious lesions in the contralateral breast was 0.2 (range, 0–2). Thirty-nine patients (33.3%) had at least one new abnormality in either breast identified by MRI, and 12 patients (10.3%) had multiple new lesions identified. Six patients (5.1%) were found to have a larger primary tumor than expected by mammography and/or sonography. Histologic findings in these cases were invasive ductal cancer (n = 3), invasive lobular cancer (n = 2), and ductal carcinoma in situ (n = 1).

Table 1.

Primary indication for MRI in 117 patients

Indication for MRI	Number of patients
Assessment for breast-conserving surgery	36
Assessment for partial breast irradiation	35
Dense, nodular breast tissue	32
Baseline prior to neoadjuvant chemotherapy	8
Strong family history of breast cancer	3
Occult primary tumor	1
BRCA mutation carrier	1
Invasive lobular cancer	1

Table 2.

Histologic findings for primary lesion

Histologic finding	Number	%
Ductal carcinoma in situ	18	15
With microinvasion	1	0.8
Invasive ductal carcinoma	71	61
With other features∗	15	13
Invasive lobular carcinoma	12	10

∗Ductal carcinoma with medullary, lobular, mucinous features.

Biopsies generated as a result of the MRI findings are listed in Table 3. Twenty-seven patients (23.1%) had a biopsy as a result of MRI findings. Ten patients required additional MRI-guided biopsies in the ipsilateral breast, and three patients underwent MRI-guided biopsy in the contralateral breast. Six patients (5.1%) required more than one biopsy overall in either breast. Pathologic findings from new lesions identified by MRI are described in Table 4. Additional foci of cancer were identified in 17 patients (14.5%), 12 (10.3%) in the ipsilateral breast and 5 (4.3%) in the contralateral breast.

Table 3.

Abnormalities and biopsies resulting from MRI in 117 patients

Category	Number
Ipsilateral breast
Patients with new abnormalities	27 (23.1%)
Ultrasound-guided biopsies	10 (8.5%)
MRI-guided biopsies	10 (8.5%)
Contralateral breast
Patients with new abnormalities	19 (16.2%)
Ultrasound-guided biopsies	12 (10.3%)
MRI-guided biopsies	3 (2.6%)
Total
Patients with at least one new abnormality	39 (33.3%)
Patients undergoing any biopsy	27 (23.1%)
Patients undergoing >1 biopsy	6 (5.1%)

Table 4.

Pathologic findings for 32 foci biopsied from 27 patients after abnormalities were identified on MRI

Pathologic finding	Number of foci
Malignant	14 (44%)
Infiltrating ductal	11
Infiltrating lobular	1
Ductal carcinoma in situ	2
Benign	18 (56%)
Papilloma	4
Stromal fibrosis	3
Ductal/lobular hyperplasia	3
Fibrocystic changes	3
Fibroadenoma	2
Sclerosing adenosis	2
Cyst	1

The positive predictive value of MRI to detect additional malignant disease was 0.60 (confidence interval [CI], 0.32–0.84) in the ipsilateral breast, 0.67 (CI, 0.38–0.88) in the contralateral breast, and 0.63 (CI, 0.44–0.80) overall.

The MRI provided information that altered the clinical management of these patients in 23 cases (19.7%). More extensive primary tumors were demonstrated in 6 patients (5.1%), all of whom underwent a mastectomy. Of the 17 patients found to have additional foci of cancer, 15 were treated with mastectomy and 2 underwent bilateral lumpectomy. Five patients chose to undergo mastectomy based on the initial MRI suspicion of multicentric or extensive cancer in the ipsilateral breast prior to a confirmatory biopsy. In all cases, the final pathologic findings correlated with the MRI suspicion of multiple foci or extensive cancer.

DISCUSSION

A recent publication in the New England Journal of Medicine by Lehman et al described the utility of breast MRI for detecting contralateral cancers in patients presenting with primary breast cancer (7). Additional contralateral foci of cancer were identified in 3.1% of patients. The sensitivity in the contralateral breast was 91% and the specificity was 88%. The negative predictive value of MRI was 99%. This study did not evaluate additional foci of tumor in the ipsilateral breast, however. Wiener et al studied 65 patients with bilateral MRI in addition to mammography and ultrasound upon presentation with breast cancer (8). Another focus of breast cancer was found in the ipsilateral breast in 32% of patients and in the contralateral breast in 9% of patients. Drew et al compared MRI with mammography, sonography, and physical examination in preoperative patients (9). They found that the sensitivity for detecting multifocal breast cancer was 100% for MRI and 18% for standard modalities.

A criticism of MRI has been its lack of specificity, which varies in the literature from 31% to 91% (10). Mammography, on the other hand, has a specificity of 93% to 99%. From a practical standpoint in the current study, in some patients, the MRI added to the need for biopsies yet did not change the overall management. Certainly, additional biopsies increase the cost of treatment and contribute to the anxiety of the patient with newly diagnosed breast cancer. A bilateral MRI costs approximately $1100, and an ultrasound- or MRI-guided biopsy costs approximately $1000. The cost savings of preventing the clinical appearance of occult breast cancer is undefined.

While MRI is effective in detecting breast cancer, its specificity for screening is much lower than that of mammography. The need for additional imaging ranged from 8% to 17% in MRI screening studies, and the biopsy rates ranged from 3% to 15% (11–15). The rate of false-positive results is higher in women who undergo screening compared with a high-risk population. An American Cancer Society review found that the higher rate of biopsies and additional studies was acceptable in women with a high risk of breast cancer but inappropriate in low-risk women (6). The authors advised against using MRI for screening since the harm of additional testing and procedures in these low-risk women would outweigh the benefits.

The finding of additional foci of cancer or more extensive cancer directly impacts the surgical treatment of breast cancer. In this study, new findings of cancer occurred more than twice as often in the ipsilateral breast as in the contralateral breast. Indeed, many patients, as evidenced in this study, will choose a mastectomy based on this information. Caution must exist, however, in recommending mastectomy based on MRI findings alone without pathologic confirmation of cancer. One criticism of breast MRI has been whether the small focus of cancer that it detects is relevant. MRI appears to detect other foci of cancer up to 30% of the time; however, the long-term local failure rate following breast-conserving surgery is far less than 30% (16). This suggests that breast radiation may be effectively treating small foci of cancer.

Many patients in this study underwent MRI to determine their suitability for partial breast irradiation following lumpectomy. A concern about omitting whole-breast radiation is that small foci of cancer will be left without local treatment. We have had the policy of confirming that no other foci of cancer exist by MRI before proceeding with partial breast irradiation.

Breast MRI adds an important tool to preoperative evaluation in selected breast cancer patients and directly impacts surgical management in a significant number. MRI is optimally performed at centers experienced in the technique utilizing dedicated breast MRI equipment and with capability to perform MRI-guided biopsies when lesions cannot be identified with any other imaging modality.

CONCLUSION

Breast MRI adds an important tool to preoperative evaluation in selected breast cancer patients and directly impacts surgical management in 20% of patients. Further studies will help define the optimal selection criteria for this imaging modality.