Correlation Between Margin Status and Ipsilateral Breast Tumor Recurrence in Patients With Breast Cancer Undergoing Breast-Conserving Surgery With Whole-Breast Radiation Therapy.

purposeBreast-conserving surgery (BCS) with whole-breast radiation therapy is the standard treatment for invasive breast cancer, with surgical margin status crucial for minimizing ipsilateral breast tumor recurrence (IBTR). This study aimed to reassess IBTR, considering breast's three-dimensional structure and the unclear significance of superior and deep margins.

methodsWe analyzed 3,712 patients who underwent BCS at Samsung Medical Center (2011-2015), excluding those with metastatic disease, neoadjuvant chemotherapy, bilateral cancer, or benign tumors. IBTR was defined using two criteria: 1) 90-degree angle (IBTR⁹⁰), and 2) 120-degree angle (IBTR¹²⁰), based on the directional location of recurrence relative to the original tumor site. Margin status was evaluated by resection distance and categorized as positive, close (less than 1 mm, excluding positive margins), 1 mm, 2 mm, or > 2 mm.

resultsThis study included 3,712 patients, with a median follow-up of 101 months. Local and distant recurrences occurred in 89 of 3,712 (2.4%) and 101 of 3,712 (2.7%) patients. Using the IBTR⁹⁰ definition, the IBTR rate was the highest in the close margin group (7/219, 3.2%) and increased to 4.6% (11/238) with the 120-degree angle definition. A statistically significant difference in IBTR¹²⁰ rates was observed between margin positive or close margin cases (3.5%) and other margin statuses (1.8%) when superficial and deep margins were excluded (

conclusionIBTR rates were higher in close and positive margin groups under the 120-degree definition, particularly when superficial and deep margins were excluded. Although positive margins did not always show the highest recurrence, margin status still influenced IBTR risk. Re-excision should be individualized based on imaging, pathology, and clinical judgment.