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Effect of Breast Magnetic Resonance Imaging on the Clinical Management of Women With Early-Stage Breast Carcinoma

From the Department of Radiation Oncology and the Department of Radiology, University of Pennsylvania School of Medicine, Philadelphia; and Department of Mathematics, Millersville University, Millersville, PA.

Address reprint requests to Lawrence J. Solin, MD, Department of Radiation Oncology, Hospital of the University of Pennsylvania, 3400 Spruce St, Philadelphia, PA 19104; e-mail: solin{at}xrt.upenn.edu

	ABSTRACT

TOP ABSTRACT INTRODUCTION PATIENTS AND METHODS RESULTS DISCUSSION REFERENCES

 
PURPOSE: To determine the impact of breast magnetic resonance imaging (MRI) on the clinical management of patients with early-stage breast cancer.

PATIENTS AND METHODS: A review was performed of the records of 207 women with early-stage breast cancer (including five women with bilateral disease) who underwent breast MRI during work-up for breast conservation treatment. All patients presented with clinical stage 0, I, or II disease. For each patient, a determination was made whether the breast MRI affected the clinical management, and if so, whether the patient was well served by the change in management.

RESULTS: The MRI findings affected the clinical management in 43 cases (20% of 212 breast cancers). Based on the pathology findings and the overall clinical course for each case, the breast MRI was judged to have had a strongly favorable effect on management in 18 cases (8%), a somewhat favorable effect in six cases (3%), an uncertain effect in five cases (2%), a somewhat unfavorable effect in 11 cases (5%), and a strongly unfavorable effect in three cases (1%). The effect of MRI was not significantly different for invasive carcinoma compared with ductal carcinoma-in-situ (all P .27). However, the effect of MRI was significantly greater when the MRI was performed before an excisional biopsy (P = .0011) or for larger tumors (P = .0089).

CONCLUSIONS: Breast MRI alters the clinical management for a sizable fraction of women with early-stage breast cancer and appears to offer clinically useful information for determining optimal local treatment.

	INTRODUCTION

TOP ABSTRACT INTRODUCTION PATIENTS AND METHODS RESULTS DISCUSSION REFERENCES

 
MAGNETIC RESONANCE imaging (MRI) of the breast is increasingly used as a tool for detecting breast cancer. The main strengths of MRI include its exquisite delineation of soft tissue and its ability to image the breast in fine sections and in multiple planes, providing three-dimensional information. Numerous studies in the diagnostic setting that correlated the radiologic findings of MRI to corresponding pathology sections have been conducted and have estimated MRI sensitivity rates for detecting invasive breast cancer as 95% to 100%.^1-7 This figure corresponds extremely favorably with the sensitivity of mammography, which is approximately 85%.⁸ Specificity, however, has been one obstacle thus far to the widespread use of breast MRI. Reported specificity rates have been extremely variable (37% to 97%), depending on the technique used to image the breast, the settings used for each imaging parameter, and whether the interpretation criteria used to determine the level of suspicion of an MRI finding were based on the pattern and degree of lesion enhancement after contrast administration or morphologic features of the lesion.^1-7

The risk-benefit ratio of breast MRI will ultimately determine its utility in the work-up and staging of patients with early-stage breast cancer. The extreme sensitivity of MRI is expected to help identify otherwise occult areas of breast cancer that are more extensive than appreciated on mammography, leading to local treatment decisions that take into account the full extent of disease in the breast, and perhaps sparing women multiple surgical procedures. Suboptimal specificity, however, tempers this benefit by exposing women to the risk of unnecessary biopsies. The balance between these patient outcomes is critical in judging the value of breast MRI.

The purpose of the present study is to assess the effect of integrating breast MRI studies into the clinical evaluation of women with early-stage breast cancer. The Hospital of the University of Pennsylvania has significant experience in performing breast MRI studies, and because of the varying ways that patients presented, the MRI studies were performed at various points in the course of clinical management. The present study reports data on the frequency with which the breast MRI prompted or hastened changes in patient management, the specific nature of these changes, and, most importantly, whether the women were well served by these MRI-prompted or MRI-hastened changes.

	PATIENTS AND METHODS

TOP ABSTRACT INTRODUCTION PATIENTS AND METHODS RESULTS DISCUSSION REFERENCES

 
An analysis was conducted of the records of patients with early-stage breast carcinoma who underwent breast MRI from November 1992 through June 2000 during work-up for breast conservation treatment (ie, breast-conserving surgery followed by definitive radiation treatment) at the Hospital of the University of Pennsylvania. The study population consisted of a consecutive series of 207 women, including five women with bilateral synchronous or metachronous breast cancer, for a total of 212 cases of breast cancer evaluated by MRI. The patients were consecutive cases of patients with breast MRI studies evaluated for breast conservation treatment by a single radiation oncologist (L.J.S.) experienced in breast cancer treatment. Patient information was recorded from patient charts, radiology reports, and pathology reports.

To be included in the study, all patients: (1) were diagnosed with either ductal carcinoma-in-situ (DCIS; intraductal carcinoma) or invasive carcinoma; (2) had American Joint Committee on Cancer (AJCC) clinical stage 0, I, or II disease at presentation (Tis N0 M0, T1 N0 M0, T1 N1 M0, T2 N0 M0, or T2 N1 M0)⁹; (3) had their breast MRI studies performed at the Hospital of the University of Pennsylvania; and (4) had their definitive local treatment of mastectomy or breast conservation treatment performed at the Hospital of the University of Pennsylvania. The study population was not limited to patients with difficult management decisions.

Excluded from the study were: (1) patients with a breast lesion not diagnosed as breast cancer; (2) patients who went directly to mastectomy without consultation by radiation oncology for consideration of breast conservation treatment; (3) patients who had their MRI studies after neoadjuvant chemotherapy or after breast irradiation; (4) patients with local recurrence after breast conservation treatment; (5) patients evaluated for presumed occult primary breast carcinoma on the basis of axillary lymphadenopathy with negative mammogram findings; (6) patients with lobular carcinoma-in-situ or Paget’s disease of the nipple (AJCC stage Tis N0 M0); and (7) patients with locally advanced disease at presentation (AJCC stage T3-4 and/or N2-3). Not included in this study were otherwise eligible patients who did not undergo a breast MRI study. An early clinical analysis of patients included in the present study has been reported previously.¹⁰ Six patients with clinical T2 lesions, but pathologic T3 lesions, were included in the present study. An analysis of patients evaluated for occult primary breast carcinoma has been reported previously.¹¹

Patients underwent their breast MRI studies at various points during their clinical management: (1) after a mammogram suggestive of disease, but before any tissue diagnosis; (2) after a core biopsy or fine-needle aspiration, but before excisional biopsy; (3) after an excisional biopsy that resulted in positive or close surgical margins, but before re-excisional biopsy; (4) after an excisional biopsy, with no re-excision performed; or (5) after a re-excisional biopsy. In the majority of patients (177 of 207, 86%), the MRI was performed of the entire ipsilateral breast; 29 patients (14%) also underwent an MRI study of the contralateral breast, and one patient (less than 1%) underwent an MRI that evaluated only the area of the ipsilateral breast lesion suggestive of disease.

Each MRI of the breast was performed on a Signa system (GE Medical Systems, Milwaukee, WI) with a 1.5-Tesla magnet. Patients were imaged in the prone position by use of a dedicated multicoil array system developed in-house consisting of two coils on each of two plates.^7,11-18 Gentle compression was applied to each breast between medial and lateral plates. The compression multicoil array system served to increase the signal-to-noise ratio, minimize patient motion, and decrease the image acquisition time needed to cover the volume of breast tissue. The MRI protocol evolved over time with changes in available software, increasing resolution and decreasing image acquisition time.^7,11-18 Contrast enhancement was obtained by the administration of 20 mL of gadopentetate dimeglumine (Magnevist; Berlex Laboratories, Wayne, NJ) and a subsequent saline flush. For patients who required MRI-guided wire localization of a lesion identified on MRI, a proprietary MRI needle-localization system was used.^12,13

The MRI scans were prospectively interpreted by one or two radiologists (S.G.O. and M.D.S.) experienced in reading breast MRI studies. The method of MRI scan interpretation has been reported previously.^7,11-18 The MRI reports issued by the radiologists included: (1) description of the morphology and estimated size of the primary tumor; (2) description of any additional areas in the breast suggestive of disease separate from the primary tumor; and (3) interpretation of whether the findings were likely to represent invasive cancer, intraductal carcinoma, or benign disease. Architectural features that were reported as suggesting invasive breast cancer included an enhancing mass with irregular or spiculated borders, a mass that demonstrated preferential enhancement at the periphery, and regional enhancement (ie, focal, but not masslike, enhancement in one area of the breast). Architectural features that were reported as suggestive of DCIS included linear (ductal) enhancement and regional enhancement. Architectural features that were reported as benign or likely benign included a mass with smooth or lobulated borders, a mass demonstrating no contrast enhancement, a mass with non-enhancing internal septations, and patchy parenchymal enhancement. Examples of the interpretations included "no suspicious enhancement seen," "enhancement which is likely benign," "likely benign, but cannot rule out cancer," "suspicious for cancer," "consistent with cancer," or "almost certainly represents cancer." The radiologists were aware of the results of prior radiologic studies and clinical findings at the time of the MRI readings. All interpretations were rendered before the surgical biopsies or mastectomies were performed. No specific surgical recommendations were made by the radiologists as to the suitability of patients for breast conservation treatment versus mastectomy. The MRI findings were used for clinical management in conjunction with all other information available to the clinicians who had requested the MRI studies.

A judgment was made for each case as to whether the MRI findings caused any change in the patient’s local management. In cases where MRI simply confirmed information already obtained by mammogram, ultrasound, or clinical examination, the MRI was judged to have had no effect on clinical management. The MRI was also judged to have had no effect on clinical management if the MRI findings were discordant with other information, but were not acted on. These determinations reflected the fact that MRI findings were used by clinicians in concert with several other radiologic and clinical pieces of information. For cases in which MRI was judged to change a patient’s management, the change was considered to be prompted by MRI if the MRI was the critical source of information that resulted in the alteration in management. In other cases, the MRI augmented previous equivocal information, with the result of swaying a decision toward a particular treatment or accelerating this decision; in these cases, the MRI was considered to have hastened such changes, rather than prompting them. These judgments were clear in most cases; in any ambiguous case, consideration was given to what the clinicians presumably would have done in the absence of the MRI findings.

For the women whose management was affected by the MRI, a determination was made for each patient as to whether or not she was well served by the specific change. These determinations were made on the basis of the surgical pathology findings, both gross and microscopic, that resulted from the MRI-prompted or MRI-hastened surgery, as well as by the overall clinical course. These determinations were then grouped into favorability ratings that were categorized as strongly favorable, somewhat favorable, uncertain, somewhat unfavorable, and strongly unfavorable.

Cases that were scored as strongly favorable on the basis of the MRI findings included patients for whom: (1) the MRI findings prompted or hastened a biopsy that otherwise would not have been performed, and for which the additional excised tissue was positive for cancer; (2) the MRI findings prompted or hastened a mastectomy that revealed the presence of significant residual disease in the breast (eg, extensive microscopic disease, gross multifocal disease, or gross multicentric disease) that would not have been removed by excisional biopsy or re-excision; or (3) the MRI findings prompted the surgeon to widen the excision or excise an additional area at the time of excision, with the resultant pathology revealing cancer in the additional resected tissue. Cases that were scored as somewhat favorable on the basis of the MRI findings included patients for whom: (1) the MRI served as an aid before surgery in localizing the tumor in three dimensions because of mammographic limitations (eg, lesion visible only on a single mammographic view or prior unsuccessful mammographic needle localization procedure performed); or (2) the MRI findings were diagnostically benign such that a biopsy was spared for a lesion that would otherwise have required a biopsy. Cases that were scored as uncertain on the basis of the MRI findings included patients for whom mastectomy was prompted or hastened by the MRI findings, and the disease found on pathology might or might not have been managed equally well by breast conservation treatment on the basis of the size or location of disease.

The MRI was considered to have a somewhat unfavorable effect for the patients who had a negative biopsy based on a false-positive MRI finding, but who were still able to conserve their breasts. These women underwent an extra surgical procedure of a negative breast biopsy, but ultimately underwent breast conservation treatment. Cases that were scored as strongly unfavorable on the basis of the MRI findings were patients for whom a mastectomy was performed on the basis of the MRI findings, and for whom the mastectomy pathology findings were minimal or no residual disease, and therefore, these patients could have been managed by breast conservation treatment. Details of these cases are provided in the Results.

Early in the study period, each patient signed an investigational review board-approved informed consent to undergo breast MRI imaging through various research protocols. Over time, the patients have come to represent a mix of research patients and clinical, nonresearch patients who were referred for MRI during their work-up for early-stage breast cancer. For all patients, however, the breast MRI was considered a potential source of information to aid in their clinical management. P values were determined by the ² test or Fisher’s exact test.

	RESULTS

TOP ABSTRACT INTRODUCTION PATIENTS AND METHODS RESULTS DISCUSSION REFERENCES

 
Patient and tumor characteristics according to pathologic diagnosis are listed in Table 1. The median age of the patients was 50 years (mean, 52 years; range, 23 to 79 years). The pathologic diagnosis was invasive carcinoma in 81% of cases (n = 171) and intraductal carcinoma in 19% (n = 41). Overall, 76% of the 212 cases were ultimately treated with breast conservation treatment and 24% with mastectomy.

The effect of breast MRI on the clinical management of the total study population is shown in Fig 1. Overall, 20% of the cases (n = 43) had changes in management that were based on the breast MRI findings. Eighty percent of the cases (n = 169) did not have a change in management based on the breast MRI findings.

View larger version (38K): [in this window] [in a new window]   Fig 1. Effect of breast MRI on clinical management: 80% not affected (n = 169); 20% affected (n = 43).

An additional six patients had MRI-prompted biopsies, and one patient underwent an MRI-hastened biopsy, all of which were positive for carcinoma, and all of which were judged to have had a strongly favorable effect from their respective MRI studies. In three of these seven patients, the MRI findings caused the surgeons to take wider excisions to remove the areas suggestive of disease en bloc with the main mass, avoiding a separate surgical site: in one patient, the MRI allowed the en bloc removal of two malignant satellite lesions along with the main lesion; in a second patient, the wider excision removed extensive invasive lobular carcinoma scattered diffusely throughout the specimen; and in the third patient, the widened excision yielded an additional focus of DCIS. For the four other biopsies, all of which involved a separate surgical site, the pathology findings were, respectively, a small focus of intraductal papillary cancer in a separate quadrant of the breast; a 7 mm infiltrating ductal and lobular carcinoma; multifocal DCIS; and a 1.4 cm infiltrating ductal carcinoma.

Six patients (n = 3%) were judged to have been somewhat favorably served by the changes caused by their breast MRI studies. These included four patients for whom the MRI helped localize malignant areas of disease that were suggestive of disease on mammogram but that were not easily localized with mammography (eg, lesions best observed on only one view, or lesions for which previous mammographic needle localization was unsuccessful). In addition, two patients were spared biopsies because the MRI findings were of low suspicion. For one patient, mammography revealed calcifications located apart from the main tumor mass, and biopsy was recommended to exclude multifocality. The second patient had an outside mammogram and ultrasound that suggested the possibility of a second mass. In both patients, the MRI revealed no findings suggestive of disease in the areas of concern, and therefore, these two patients underwent breast conservation treatment and were spared a second biopsy, or perhaps even a mastectomy. At the time of last follow-up examination, the two patients were alive and without relapse 12 and 27 months, respectively, after breast conservation treatment.

There were five patients (2%) with management changes that were difficult to categorize as favorable or unfavorable; all five of these patients underwent mastectomies, with residual disease that might or might not have been managed equally well with breast conservation treatment. These five patients had either residual invasive carcinoma (n = 4) or DCIS (n = 1), with tumors measuring less than 5 cm, and two of these five patients had multifocality in the region of the biopsy cavity.

Five percent (n = 11) of the total study population was judged to be somewhat unfavorably affected by the management changes made on the basis of their MRI studies; 10 of these patients underwent biopsies for areas that suggested disease on MRI that were negative on pathology. These women were therefore somewhat unfavorably affected in that they underwent additional surgery, but were still able to conserve their breasts. The one remaining patient had an area suggestive of disease excised en bloc with the main tumor mass and therefore did not undergo a separate surgical procedure.

Three women (1% of the total) were judged to be strongly unfavorably affected by the changes in their management; these were patients in whom the MRI findings prompted mastectomies (n = 2) or hastened a mastectomy (n = 1), but the subsequent pathology of the mastectomy specimens revealed that mastectomy was not required for local treatment. In one patient, the MRI demonstrated multiple rim-enhancing lesions, but the mastectomy specimen contained only a primary 2 cm infiltrating ductal carcinoma with DCIS. A second patient had multiple positive margins of resection on a re-excisional biopsy, followed by an MRI that suggested extensive residual DCIS; the mastectomy specimen contained only a single microscopic focus of residual DCIS. The third patient had an excisional biopsy with multiple close margins followed by an MRI that was suggestive of multifocal residual disease. Mastectomy was recommended because it would not have been possible to have excised all of the potential areas of disease along with the re-excision of the primary tumor site with adequate cosmesis. The mastectomy specimen revealed no residual tumor, only multiple fibroadenomas and fibrocystic changes with papillary apocrine metaplasia. This patient also underwent a prophylactic contralateral mastectomy for lobular carcinoma-in-situ. In this case, the MRI prompted a mastectomy, and possibly hastened a contralateral mastectomy as well, whereas the most likely clinical course in the absence of the MRI would have been a re-excision based on multiple close margins.

Invasive carcinoma and DCIS are compared in Table 3. Comparison of the women with invasive carcinoma to the women with DCIS revealed no significant difference in the rate of having a change in management on the basis of MRI findings (22% v 15%, respectively; P = .32). Similarly, the favorability of MRI-affected changes among patients with invasive carcinoma versus patients with DCIS was not significantly different (P = .27).

Women who had their MRI studies performed earlier in the study period (1992 to 1996) were more likely to have their management altered by MRI than were women who had their MRI studies performed later in the study period (1997 to 2000) (27% v 16%, respectively; P = .045). For those patients for whom management was altered by MRI, there was no difference in the favorability ratings (P = .13). In the earlier years of the study period (1992 to 1996), 52% (12 of 23) of the MRI-prompted changes were judged favorable and 43% (10 of 23) were unfavorable, with 4% (one of 23) of uncertain value. In the more recent years (1997 to 2000), 60% of the changes (12 of 20) were favorable, and 20% (four of 20) were unfavorable, with 20% (four of 20) of uncertain value.

The outcomes of all MRI-prompted or MRI-hastened surgeries are listed in Table 5. Among the 24 patients who had MRI-prompted or MRI-hastened biopsies performed, 12 were positive for cancer and 11 were negative for cancer; in addition, in one patient, two MRI needle-localized biopsies were performed in the same breast during the same surgery, with one biopsy positive for invasive carcinoma and the other biopsy negative (bringing the total to 13 positive and 12 negative biopsies among 24 patients). Among the 19 MRI-prompted or MRI-hastened mastectomies, 18 of the mastectomy specimens were positive for invasive carcinoma or DCIS, and one mastectomy specimen was negative for cancer.

	DISCUSSION

TOP ABSTRACT INTRODUCTION PATIENTS AND METHODS RESULTS DISCUSSION REFERENCES

Several studies have suggested that MRI is superior to mammography in delineating the extent of disease in the breast.^3,19 In several instances in the current study, the surgeons widened the excision specimen on the basis of MRI findings and were consequently able to remove the main lesion more completely or to remove a satellite lesion or lesions in a single procedure; this algorithm for patient management has obvious benefits, such as avoiding additional surgeries to re-excise for positive or close margins and increasing the possibility of removing a satellite lesion or lesions during a single surgery while conserving the breast.

Specificity continues to be a limitation of breast MRI. In the present study, 5% of the study population underwent biopsies for abnormal MRI findings that were negative on pathology. The histologic findings in these patients included atypical ductal hyperplasia, atypical lobular hyperplasia, proliferative fibrocystic changes, fat necrosis, adenosis, and papillary apocrine metaplasia. Many studies have documented the postcontrast enhancement of benign lesions and even benign breast tissue stimulated from hormone replacement therapy.^1,6,16,20,21 The basis of enhancement is clearly not specific to malignancy per se, but rather relates to a number of factors including the vascularity of lesions and the permeability of the vessels. Invasive breast carcinomas often show increased vascularity, with an increase in the permeability of this neovascularity, leading to an early uptake and early wash-out phenomenon.^1,2,4,20 Invasive breast carcinomas also tend to have increased vascularity at the periphery, leading to a rim-enhancing pattern on MRI. The pattern of enhancement in DCIS can be variable, including both ductal and regional enhancement.^6,7,12 However, variable histologic findings for both malignant and benign lesions result in overlap of the MRI enhancement patterns, thereby reducing specificity.^3,20

The issue of specificity and false-positive MRI findings must be considered in the context of other breast imaging modalities. Mammography in the diagnostic setting has a positive predictive value ranging from 10% to 40%; thus, most mammographically driven biopsies will be negative on pathology.⁸ Although maximizing the specificity is an important goal, in any diagnostic modality there will be a (preferably small) percentage of false positives. In setting the threshold to minimize undetected disease, for example, for patients undergoing breast conservation treatment, some unnecessary procedures will occur. Clearly, the strength of MRI lies in its sensitivity of nearly 100%, and the tradeoff between sensitivity and specificity needs to be considered in the clinical setting of optimizing patient management.

The question of which patients are most likely to benefit from MRI has important implications for patient selection. MRI was more likely to benefit patients with larger tumors (P = .0089) and patients for whom the MRI had been performed before excisional biopsy (P = .0011) (Table 4). The benefit of MRI was not different for a number of subgroups that a priori might have been expected to have benefited most, for example, younger patients age 35 years or patients with negative mammograms (all P .18).

In the present study, the MRI was more likely to have had an impact on clinical management when the MRI was performed after an abnormal mammogram but before excisional biopsy, when the surgical plan could be easily adjusted on the basis of new MRI findings. Although MRI was also commonly performed before re-excision in the case of positive or close surgical margins, these cases were less likely to involve an MRI-prompted change in management; this finding may relate to the current limitations of MRI in distinguishing minimal residual disease from normal postoperative changes after excision, making it difficult to rely solely on the MRI as the basis for deciding whether to perform re-excision. The normal enhancement of granulation tissue around the excision cavity limits the predictive value of enhancement in this setting; a frequent MRI interpretation in these cases was "rim enhancement that may be consistent with postsurgical change, although residual disease cannot be excluded." However, excluding diffuse disease before proceeding with re-excision is a strong rationale to perform MRI at this point in the management. Previous work on this specific use of breast MRI has suggested that MRI may be useful in predicting residual disease before re-excision, with a positive predictive value of 82% and a negative predictive value of 61%.¹⁷

The patients with DCIS were slightly, but not statistically, less likely to have had their management affected by their MRI studies than were the patients with invasive carcinoma (15% v 22%, respectively; P = .32); however, patients with DCIS were slightly more likely to have had their MRI studies performed after excisional biopsy (66% v 49%, respectively). Of the six cases in which patients with DCIS had their management changed by MRI, five were judged to be strongly favorable. Previous studies evaluating the use of breast MRI in patients with DCIS have reported variable levels of sensitivity (66% to 100%) in small numbers of patients, and have found that MRI was more accurate than mammography in describing the extent of DCIS.^18,22,23

A cost-benefit calculation for integrating breast MRI into the routine work-up of the patient with a symptomatic breast or being considered for breast conservation treatment must balance the costs of conducting the MRI (including equipment acquisition, radiology fees, surgically related and pathology-related costs of any additional biopsies) against the expected cost savings of guiding patients to the appropriate initial local management on the basis of a more complete assessment of the extent of disease, as well as the potential avoidance of local recurrence after breast conservation treatment. A cost-benefit analysis of breast MRI as a preoperative staging tool at the University of California at San Francisco found that the expected cost savings resulting from breast MRI studies surpassed the expected costs incurred; these calculations underscore the potential cost savings of avoiding repeated re-excisions with accurate preoperative information regarding the extent of disease.¹⁹ Costs of MRI will likely be further reduced as breast MRI technology evolves. One promising area is the development of MRI-compatible core biopsy systems. Stereotactic core needle biopsy for lesions found during mammography has been shown to spare 81% of open biopsies and have an extremely low false-negative rate of approximately 0.5%.^24-26 The ability to evaluate lesions on MRI with large core needle biopsy will increase the specificity of the breast MRI procedure and decrease the use of open surgical biopsies for false-positive MRI findings; the availability of an MRI core biopsy system will also decrease the likelihood of performing mastectomy on the basis of MRI suspicion of multifocality in the absence of actual tissue sampling to confirm multifocal disease.

The current study has several limitations. First, these data represent the experience from a single institution using breast MRI for women with early-stage breast cancer. The techniques currently used to perform breast MRI vary considerably among institutions; these variables include magnetic field strength, coil configuration, and imaging parameters such as section thickness, repetition time, echo time, imaging matrix, field of view, and time of acquisition. This lack of uniformity may limit the ability to generalize these findings to institutions that employ different techniques. Efforts at standardization are underway, including: the use of breast MRI according to guidelines for appropriate clinical indications; minimal technical requirements for acquiring high quality images; techniques for performing the MRI scan; a lexicon to describe lesions uniformly and reproducibly; and clear interpretation criteria for radiologists to use in reporting breast MRI results.^27-30 Over time, breast MRI will likely advance as a tool with uniform standards comparable to those used in mammography. Therefore, the data from the present study suggest the potential broader impact of breast MRI.

In addition to differences in technique, there is undoubtedly a learning curve within each institution as the clinicians and radiologists come to understand over time how best to integrate the MRI findings into the overall clinical picture for each patient. In the present series of patients, the breast MRI examinations were integrated into the clinical management by a team of dedicated breast cancer specialists. Evidence for a learning curve in the present study is that the early cases in this series were more likely to be affected by breast MRI, and that these effects were more likely to be unfavorable than in later years. By including data from the earliest patients in this analysis, the overall data might reflect a different view of the impact of breast MRI than that observed in current practice.

Last, the cases analyzed in the present study were patients who presented to radiation oncology for evaluation for breast conservation treatment. Those patients whose MRI findings caused them to go directly to mastectomy without any intermediate consideration of breast conservation treatment were not included; the absence of such patients from the present study may have diminished the impact of breast MRI from what would otherwise be expected, for example, on the basis of a wider study population of patients presenting with early-stage breast cancer to surgical practices. Alternatively, patients may have been excluded from consideration of breast conservation treatment by use of conventional methods of evaluation, such as physical examination, mammography, and ultrasound with no substantial change in the impact of breast MRI as seen in the present study.

The assumption that identifying occult multifocal or multicentric disease will lead to better outcomes by improving local control warrants careful consideration. Pathologic examination of mastectomy specimens of patients deemed eligible for breast conservation treatment has revealed significant rates of multifocality, not all of which were located close enough to the reference tumor to fall within the presumed surgical volume for lumpectomy.³¹ However, multiple long-term outcome studies have demonstrated that breast conservation treatment and mastectomy have equal rates of overall survival and distant recurrence, and that breast conservation treatment is associated with low rates of local recurrence.^32-36 The discrepancy between the figures cited for undetected multifocality and the low actual local recurrence rates after breast conservation treatment underscores that not all undetected malignant foci will lead to local recurrence when definitive radiation is used. Therefore, when judging the clinical significance of residual disease in the breast, one must consider the extent of residual disease that can be appropriately managed with breast conservation treatment. Clearly, radiation treatment to the entire breast is able to sterilize a certain amount of microscopic disease. Gross multicentric disease, on the other hand, is a contraindication for breast conservation.^37,38 Although radiologic studies have found that MRI can depict additional cancers that are mammographically occult in 34% to 37% of patients, the threshold at which MRI findings should affect patient selection for breast conservation treatment depends on how much residual disease in the breast can be controlled with standard doses of radiation.^3,7 As such, the favorability determinations made in the present study attempted as best as possible to predict whether the amount of disease in the breast warranted mastectomy or could have been appropriately treated with breast conservation. Outcome data for the patients in the present study could potentially validate the study findings. For patients undergoing evaluation for breast conservation treatment, one question that may not be answered in a prospective, randomized trial is whether better outcomes will be achieved for patients undergoing breast MRI staging than for patients not undergoing breast MRI staging.

In summary, the present study has shown that MRI leads to a more complete assessment of the extent of disease in breast tissue. In this series, the patients overall were well served by MRI because of its sensitivity, with 8% of the study population experiencing a strongly favorable benefit and 3% a somewhat favorable benefit as a result of the greater detection of occult multifocal and extensive residual disease. This benefit was tempered somewhat by the suboptimal specificity of the test, which led to the somewhat unfavorable effect of negative biopsies in 5% of the patients, but only 1% of the study population experienced a strongly unfavorable effect as a result of the MRI. On balance, these data appear to justify the use of breast MRI. For the evaluation and staging of women with early-stage breast cancer, breast MRI appears to offer clinically useful information for determining optimal local treatment.

	NOTES

 
Presented in part at the Thirty-Seventh Annual Meeting of the American Society of Clinical Oncology, San Francisco, CA, May 12-15, 2001.

	REFERENCES

TOP ABSTRACT INTRODUCTION PATIENTS AND METHODS RESULTS DISCUSSION REFERENCES

 
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Submitted August 21, 2001; accepted May 10, 2002.

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