Risk factors for positive margin in breast conservation surgery for localized breast cancer.

Abstract

e12539 Background: Breast cancer is an evolving global concern due to its increasingly high morbidity and mortality rates. This is, in part, due to health care disparities in breast cancer patients that have been a problem for screening, diagnosis, and treatment. Breast-conservation surgery (BCS) is defined as the removal of breast tumor tissue surrounded by a margin of normal tissue and includes lumpectomy, partial mastectomy, wide excision, and segmental mastectomy. Negative margins post-BCS are necessary to avoid any breast cancer recurrence. A negative margin is defined as no gross or microscopic disease, also known as no tumor on ink. Positive margins are associated with patients who may have to undergo re-excisions with larger margins or total mastectomy, exposing patients to greater morbidity and delaying the start of adjuvant therapy. Methods: This was a retrospective cohort study designed to examine factors associated with positive margins (PM) in breast cancer patients undergoing breast-conserving surgery. The Charleston Area Medical Center cancer registry was queried from 2009-2022 for females diagnosed with invasive breast cancer who had surgery for localized disease (TxN0M0), excluding those with previous malignancies. Data were analyzed with SAS 9.4 using student’s t-test for continuous variables, Chi-square or Fisher’s exact for categorical variables, and multivariate analysis to identify factors predictive of positive margins. Results: In total, 1133 female patients with mean age of 64±11 met inclusion criteria. The positive margin group (PMG) made up 10.2% of the population while the negative margin group (NMG) was 89.8%. The PMG had significantly (p < .0001) larger tumors than the NMG, 19.7±12 and 13.8±9, respectively. Multifocal tumors made up 18% of the PMG compared to 4.4% of the NMG (p < .0001). Invasive lobular carcinoma made up 20% of the PMG compared to 7.2% of the NMG (p = .003). Recurrence was significantly (p = .030) higher in the PMG compared to the NMG, 7.4% and 3.2%, respectively; however, 5-year survival showed no difference. Regression modeling showed that multifocal tumors were 4.4 times (95% CI: 2.4-8; p < .0001) more likely to be associated with PM, lobular carcinoma was 2.8 times (95% CI: 1.6-4.8; p = .0003) more likely to be associated with PM, and stage II patients were 2.4 times (95% CI: 1.5-3.7; p = .0002) more likely to have PM. Conclusions: Univariately, tumor size, multifocality, lobular carcinoma, stage II, and local/distant recurrence were all associated with positive margins. This finding was re-demonstrated with respect to multifocality, lobular carcinoma, and stage II following multivariate analysis. The results of this study may help to guide surgeons and oncologists in the management of localized, invasive breast cancer, especially in emphasizing the importance of timely follow-up in patients at higher risk and in the education of patients regarding their care.