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Risk factors for local recurrence in patients with invasive breast cancer and negative surgical margins of excision. Where are we and where are we going?

The results of 6 prospective randomized clinical trials have clearly demonstrated that the combination of breastconserving surgery (CS) and radiation therapy (RT) provides survival rates equivalent to those observed following mastectomy. 1 Consequently, the CS-RT combination is now a standard therapeutic option for the treatment of many women with early-stage invasive breast cancer and is preferable to mastectomy because of the cosmetic benefit of breast preservation. 2 Although the CS-RT combination generally is associated with a high level of local tumor control, a recurrence develops in the treated breast in a small proportion of patients (approximately 1.0%-1.5% per year). 3 While the impact of such local recurrences on survival remains a matter of debate, 4 minimizing the risk of local recurrence in patients choosing breast-conserving therapy remains an important clinical objective. Numerous studies have indicated that most local recurrences following treatment with CS and RT are in the mammary parenchyma, at or near the primary tumor site, and that local recurrence rates are lower when a wider resection of the tumor is performed. Taken together, these observations suggest that an “adequate” excision of the primary tumor is necessary to obtain optimal local tumor control. Efforts to determine what constitutes an adequate excision before RT have focused on the identification of risk factors for local recurrence. Although a variety of clinical, treatment, and pathologic factors have been reported to be associated with an increased risk of local recurrence following CS and RT, 3 the status of the final microscopic margins of excision is among the most important of these in daily clinical practice. The technical limitations in assessing microscopic