Limited data exist regarding the associations between TROP-2 protein expression, clinicopathological characteristics, and outcome in triple-negative breast cancer (TNBC).
TROP-2 expression was determined for patients diagnosed with TNBC between 2000-2017 by immunohistochemistry (IHC) (ab227689, Abcam) on whole slide tumor sections, and assessed as continuous and categorical variables (H-score high, 201-300, medium 100-200 and low <100). Associations between TROP-2 expression and age, BMI, tumor grade and size, lymphovascular invasion (LVI), ductal carcinoma in situ (DCIS) presence, nodal status, stromal tumor-infiltrating lymphocytes (sTILs), androgen receptor (AR), standardized mitotic index (SMI), and outcome were assessed.
We included 685 patients with a median age at diagnosis of 54y (range 22-90y). TROP-2 expression was high, medium and low in 97 (16.5%), 149 (25.3%) and 343 (58.2%) of patients, respectively. The presence of LVI, associated DCIS, nodal involvement, apocrine histology and AR expression were correlated with higher TROP-2 levels. TROP-2 was not associated with pathological complete response (pCR). There were no associations between TROP-2 expression and time-to-event outcomes.
In stage 1-3 TNBC, higher TROP-2 expression was correlated with apocrine histology, higher AR expression, presence of DCIS, LVI, and nodal involvement. There was no correlation between TROP-2 expression and sTILs or outcome.