Role of primary breast cancer characteristics in predicting positive sentinel lymph node biopsy results: a multivariate analysis.

HYPOTHESIS Certain primary breast tumor characteristics can be used to predict positive sentinel lymph node biopsy (SLNB) results and thus determine which patients should undergo SLNB. DESIGN Retrospective review of patients undergoing SLNB for invasive breast cancer from March 1, 1998, through March 31, 2001. SETTING University-affiliated tertiary care hospital. PATIENTS Two hundred fifty-seven consecutive patients undergoing successful SLNB. MAIN OUTCOME MEASURES Correlation of patient age, tumor size, histological subtype, grade, lymphovascular invasion (LVI), host lymphoid reaction, border of neoplasm, characteristics of ductal carcinoma in situ, presence or absence of lobular carcinoma in situ, estrogen receptor, and her-2-neu oncogene status with positive SLNB results. Univariate and multivariate analyses were applied. Stepwise multiple logistic regression analysis identified variables predictive of positive SLNB results (P< or = .05). RESULTS : Regression analysis identified tumor size and LVI as the only variables predictive of positive SLNB results. Results of SLNB were positive in 73 (28.4%) of 257 patients (T1a, 5/37 [13.5%]; T1b, 19/93 [20.4%]; T1c, 37/103 [35.9%]; and T2, 12/24 [50.0%]). Although LVI did not correlate with tumor size, it was highly predictive of positive SLNB results by means of the following equation: 1/(1 + e(-z)), where z = 0.3079 + 1.3814 (LVI), -1.1869 (T1a), -0.3235 (T1b), or +0.5724 (T1c). CONCLUSIONS Tumor size and LVI were the only variables independently predictive of positive SLNB results. Lymphovascular invasion was the strongest predictor. These data show a higher than expected incidence of positive SLNB for all tumor sizes, which may be explained by results of immunohistochemical analysis of sentinel lymph nodes, and which suggest that all patients with invasive breast cancer should be offered SLNB. Further studies with a larger cohort of patients are warranted.