A new prospective study has found that breast cancer patients who do not obtain cancer-free surgical margins after lumpectomy have a higher risk of distant breast cancer recurrence. Patients undergoing breast conservation surgery often require additional operations to obtain cancer-free (negative) margins. The study included 437 patients with stage I to IIIA breast cancer who underwent lumpectomy between 1994 and 2004. Distant metastasis was found to be more frequent among patients with initial positive margins (15.5%) than those with initial negative margins (4.9%).

There was an even higher risk of distant metastasis (22.8%) among patients who failed to get negative margins after a second surgery to obtain clean margins. The authors conclude that residual invasive cancer found during subsequent surgery after initial positive margins is an important prognostic marker for distant recurrence.

Clean surgical margins

Positive margins are found upon pathology in approximately 30% of lumpectomies, resulting in the need for additional surgery (partial or complete mastectomy) in obtain clean margins. Patients with tumors that do not form a lump (such as lobular breast cancer), large tumors, positive lymph nodes, or mammographic microcalcifications are more likely to require additional surgeries, as do those with multifocal disease (i.e., more than one tumor in the same breast). Obtaining clean margins is very important in avoiding recurrence within the breast and may provide an overall survival benefit. Repeat surgery can also improve cancer staging and treatment to the extent that it provides a clearer indication of the size of the tumor. Based on the findings of another 2009 study, for patients with lobular or other diffuse breast cancer (in which tumors do not form a palpable lump) or whose mammograms indicate the possibility of multifocal disease, presurgical breast MRI might be useful in better defining the extent of disease and reducing the number of surgeries.