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 from 1/98–12/10. 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<.0001). Relative to TN tumors, HR+/HER2-,
HR+/HER2+, and HR-/HER2+ tumors had higher odds of demonstrating
LVI of 1.8(OR,1.8; 95% CI,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<.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.