Abstract
BACKGROUND: The ACOSOG Z0011 trial demonstrated that axillary dissection (ALND) is not necessary for local control or survival in women with T1/2cN0 cancer undergoing breast-conserving therapy. There is concern about applying these results to triple-negative (TN) cancers secondary to their high local-recurrence (LR) rate. We examined the frequency of lymphovascular invasion (LVI) and nodal metastases in TN cancers to determine whether ALND can be safely avoided in this subtype. METHODS: Data were obtained from a database of patients with invasive breast cancer treated at Memorial Sloan Kettering Cancer Center from January 1998 to December 2010. A total of 11,596 tumors were classifiable into clinical surrogates for molecular subtype by immunohistochemical analysis: hormone receptor (HR)+/HER2+, HR+/HER2-, HR-/HER2+, and TN (HR-/HER2-). Multivariable logistic regression analysis (MVA) was used to determine associations between clinicopathologic variables and subtype. RESULTS: There were differences in age, tumor size, LVI, grade, and nodal involvement among groups. On MVA controlling for size, grade, and age, ER, PR, and HER2 status were significantly associated with LVI (p < 0.0001). Relative to TN tumors, HR+/HER2-, HR+/HER2+, and HR-/HER2+ tumors had higher odds of demonstrating LVI of 1.8 (odds ratio 1.8; 95 % confidence interval 1.6-2.1), 2.5 (2.5; 2.0-3.0), and 1.7 (1.7; 1.4-2.1), respectively. On MVA adjusting for size, grade, LVI, and age, TN tumors had the lowest odds of having any or high-volume nodal involvement (≥4 nodes, p < 0.0001). CONCLUSIONS: LVI and nodal metastases were least frequent in TN cancers compared with other subtypes, despite the uniformly worse prognosis and increased LR rate in TN tumors. This suggests TN cancers spread via lymphatics less frequently than other subtypes and ALND may be avoided in TN patients meeting Z0011 eligibility criteria.