Magnetic resonance mammographyBMJ 2010; 341 doi: http://dx.doi.org/10.1136/bmj.c5513 (Published 21 October 2010) Cite this as: BMJ 2010;341:c5513
- Malcolm R Kell, consultant surgeon and senior lecturer
- 1Department of Surgery and Eccles Breast Screening Unit, Mater Misericordiae University Hospital, Dublin 7, Ireland
Magnetic resonance imaging enables high definition scanning of tissue without the use of ionising radiation. In the past decade it has become widely used in breast imaging and is a sensitive method of visualising the breast parenchyma and highlighting areas of pathology. Magnetic resonance mammography is now the optimum imaging modality when combined with mammography and ultrasound for screening women at high risk as a result of genetic abnormalities that predispose them to breast cancer.1 The technique can detect occult carcinoma not seen with conventional imaging; it is a useful imaging tool for patients who present with metastatic axillary lymphadenopathy and an occult primary tumour in the breast; and it is useful when assessing response to neoadjuvant chemotherapy. However, its routine use in the management of patients with early stage breast cancer may be unwarranted—we have no evidence to support a clear benefit in this setting⇓.
The Comparative Effectiveness of Magnetic Resonance Imaging in Breast Cancer (COMICE) trial was a multicenter randomised controlled trial conducted in the United Kingdom to assess the impact of magnetic resonance mammography in patients with breast cancer who were thought to be amenable to breast conserving treatment after standard triple assessment. Outcomes were the incidence of reoperation and mastectomy.2 The study found no difference in reoperation rates with or without magnetic resonance mammography (19% (153/816) v 19% (156/807); odds ratio 0·96, 95% confidence interval 0·75 to 1·24), although the rate of mastectomy was higher in the magnetic resonance mammography group (7% (58/816) v 1% (10/807)).2 This study is currently the only randomised controlled trial that has examined the role of preoperative magnetic resonance mammography in the management of early stage breast cancer. Results from the Mayo clinic mirror those seen in the COMICE trial; from 1997 to 2003 rates of mastectomy steadily declined from 45% to a low of 31% after which this trend reversed. By 2006 the rate had increased to 43%, and this directly correlated with an increase in the use of preoperative magnetic resonance mammography.3 This Mayo clinic trial examined patients treated at their centre and used a multiple logistic regression model to assess the effect of magnetic resonance imaging on surgery type, while adjusting for potential confounding variables. Magnetic resonance mammography identifies occult disease in the breast that may not be visible on other imaging modalities, and this may lead to inappropriate treatment decisions.
Invasive lobular carcinoma classically infiltrates the breast in a diffuse manner and may have a multicentric or a multifocal growth pattern. For this reason lobular carcinoma is commonly regarded as a good indication to perform magnetic resonance mammography. One single centre audit series found that 46% of patients with lobular breast cancer had their surgical management altered as a result of undergoing magnetic resonance mammography, although the study did not examine oncological outcome.4 Lobular carcinoma may show subtle clinical and mammographic changes, and in this setting magnetic resonance mammography is probably useful when planning treatment, although high quality evidence showing that the routine use of this technique improves patient is lacking.
Advocates of magnetic resonance mammography suggest that identifying otherwise occult disease in the breast may improve oncological outcome, an early marker of which is disease recurrence in the treated breast. Combined analysis of patients with early stage disease from the national surgical adjuvant breast and bowel project (NSABP), before the use of magnetic resonance mammography, has shown low rates of recurrence—5% at 10 years in patients receiving optimum multimodal treatment.5 With such low rates, recurrence in the treated breast is unlikely to be improved greatly by the use of this new technique.
Furthermore, recent data suggest that the presence of specific diseases with a poor prognosis (HER2 positive disease or triple negative disease) has more effect on local control than occult disease burden; specific molecular features of the breast cancer cells are more important than the size of the tumour for the risk of recurrence. Patients with HER2 positive disease or triple negative disease (negative for the oestrogen receptor, progesterone receptor, and HER2) have dramatically higher rates of local recurrence after surgery for breast cancer.6 Radiotherapy reduces local recurrence by 66%; this effect is due to the clearance of occult low volume disease—tiny residual areas of invasive or in situ disease that without radiotherapy may evolve into recurrence.7 There is no evidence that magnetic resonance mammography will improve local control after breast conserving treatment.
Magnetic resonance mammography can also detect occult disease in the contralateral breast. Undiagnosed cancer is found in the contralateral breast in 3.1% of patients when magnetic resonance mammography is performed within one year of diagnosis.8 However, rates of contralateral disease are the same (6%) at eight years regardless of whether or not magnetic resonance mammography was performed at diagnosis.9 Occult contralateral disease detected by magnetic resonance mammography at the time of diagnosis may therefore be irrelevant. Adjuvant treatment, tamoxifen, and aromatase inhibitors all improve local and systemic control and also reduce contralateral disease. Again, the notion that detecting occult disease with magnetic resonance mammography would benefit patients was not borne out after longer patient follow-up.
Magnetic resonance mammography can detect occult disease in the breast and surpasses conventional imaging in this aim. Currently, however, there is no compelling evidence that this technique should be used routinely in patients with newly diagnosed breast cancer.
Cite this as: BMJ 2010;341:c5513
Competing interests: The author has completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declares: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.
Provenance and peer review: Not commissioned; externally peer reviewed.