Predictive factors for sentinel node metastases in primary invasive breast cancer: A population-based cohort study of 2552 consecutive patients

Background: Axillary lymph node status is one of the most important prognostic factors for breast cancer. The aim of this study was to determine predictive factors for metastasis to sentinel node (SN) in primary invasive breast cancer. Method: This is a study of 3979 patients with primary breast cancer during 2008-2013 in Malmö and Lund scheduled for surgery and included in the information retrieved from Information Network for Cancer Care (INCA). The final study population included 2552 patients with primary invasive breast cancer. The risk of metastases to SN were examined in relation to potential clinicopathological factors such as age, screening mammography, tumor size, tumor type, histological grade, estrogen status, progesterone status, Her-2 status, multifocality, and lymphovascular invasion. Binary logistic regression was used; adjusted analyses yielded odds ratio (OR) with 95% confidence interval. Results: Tumors detected by mammography screening were less likely to be associated with metastases to SN compared to those not found by mammography screening (0.63; 0.51-0.80). Negative hormonal status for estrogen associated with lower risk for SN metastases compared to tumor with positive estrogen status (0.64; 0.42-0.99). Tumors with a size more than 20 mm had higher risk to metastasize to SN (1.84; 1.47-2.33) compared to tumors less than 20 mm. Multifocality (1.90; 1.45-2.47) and lymphovascular invasion (3.74; 2.66-5.27) were also strong predictive factors for SN metastases. Conclusion: SN metastasis is less likely to occur in women with invasive breast cancer diagnosed by screening mammogram. Tumors with negative estrogen status are associated with low risk for SN metastases. Tumors larger than 20 mm, multifocality, or lymphovascular invasion are also factors associated with high risk for SN metastases.