[Magnetic resonance imaging in preoperative staging for breast cancer: pros and contras]

In oncologic patients, staging of the disease extent is of paramount importance. Imaging studies are used to decide whether the patient is a surgical candidate; if this is the case, imaging is used for detailed planning of the surgical procedure itself. Even in patients with limited prognosis, the first priority is always to achieve clear margins. Due to the widespread use of screening mammography, breast cancers are among the few cancers that are almost always diagnosed in an operable stage and are operated on with curative intention. It is well established that magnetic resonance imaging (MRI) is far superior to mammography (with and without concomitant ultrasound) for mapping the local extent of breast cancer. Accordingly, there is good reason to suggest that a pre-operative breast MRI should be considered an integral part of breast conserving treatment. Still, it is only rarely used in clinical practice. Arguments against its use are: Its high costs, allegedly high number of false positive findings, lack of MR-guided breast biopsy facilities, lack of evidence from randomized prospective trials and, notably, fear of "overtreatment". This paper discusses the reservations against staging MRI and weighs them against its clinical advantages. The point is made that radiologists as well as breast surgeons should be aware of the possibility of overtreatment, i.e. unnecessary mastectomy for very small, "MRI-only" multicentric cancer foci that would indeed be sufficiently treated by radiation therapy. There is a clear need to adapt the guidelines established for treatment of mammography-diagnosed multicentric breast cancer to account for the additional use of MRI for staging. Until these guidelines are available, the management of additional, "MRI-only" diagnosed small multicentric cancer manifestations must be decided on wisely and with caution. MRI for staging may only be done in institutions that can also offer an MR-guided tissue sampling, preferably by MR-guided vacuum assisted biopsy, to provide pre-operative histological proof of lesions visible by breast MRI alone.