Back to the Future: Why Are More Women Having Bilateral Mastectomy for Unilateral Breast Cancer?

Edibaldo Silva, MD, PhD
Published: Thursday, Jun 03, 2010

In 2002, reports by Fisher1 and Veronesi2 affirmed the long-term validity of breast-conserving surgery (BCS) for the management of early-stage breast cancer (ESBC). BCS is defined as lumpectomy with postoperative whole breast irradiation. Years earlier, in 1991, a National Cancer Institute Consensus Conference endorsed BCS over mastectomy as the preferred treatment of ESBC. Over the years, this led to a decrease in mastectomy rates. By 2003, BCS rates in the United States were approaching 69%.3 Surprisingly, this upward trend reversed after 2003, with the rate of women treated with BCS declining to 58%.4 The decrease in BCS has undermined the progress made over the last three decades in the management of ESBC, which has been firmly based on an accumulation of biological and clinical evidence of the natural history of this disease. 

It is difficult to fathom why rates of BCS are declining at a time when the average size of breast tumors in the United States is <2 cm at diagnosis. With increasingly smaller tumors, one might wonder why rates of margin positivity following BCS are as high as 31% to 50%.5,6 Nearly 50% of women who elect BCS must undergo subsequent mastectomy to clear these positive margins.7 Once informed consent has been obtained, the success of BCS is completely in the hands of the surgeon at the time of lumpectomy. This problem is not new, of course, and there are other factors that have contributed to the recidivism to mastectomy.


The Problem With the Ipsilateral Breast

The recent discovery of the potential for magnetic resonance imaging (MRI) to reveal second cancers in a breast affected by ESBC has led many clinicians to recommend and patients to choose mastectomy for this ipsilateral breast. MRI of the ipsilateral breast reveals potential second tumors in as many as 13% to 30% of patients.8,9 The fact that second lesions are often found in a breast with ESBC is actually a “rediscovery,” because Holland described this likelihood more than 20 years ago, after performing detailed serial section histologic examinations of mastectomy specimens. Holland’s data suggested that as many as two-thirds of these patients had a second lesion within the same breast, most of which were located within 4 cm of the known primary.10 Holland’s data remains timely because, at the time, it was used as an admonition about the validity of BCS. The rediscovery with MRI that many patients have second lesions in the ipsilateral breast is being revisited as a reason for the increasing conversion from BCS to mastectomy in patients with ESBC.11,12 

Paradoxically, Japanese investigators recently offered an analysis similar to Holland’s to support the use of accelerated partial breast irradiation (APBI), which spares breast tissue outside of this 4-cm radius from radiation in women who undergo BCS.13 Favorable 4-year recurrence rates of 1% have been published for APBI; patients continue to be followed, and longer outcomes associated with APBI are expected in the future.14 Not surprisingly, a recent report shows that patients selected for BCS on the basis of unifocal disease identified by MRI and similarly treated patients who undergo BCS based on unifocal disease established by routine mammography have identical local recurrence rates (3%-4%) at 8 years’ follow-up.15

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