Purpose: The value of tumor-infiltrating lymphocytes (TILs) for prediction of pathologic complete response (pCR) in breast cancer (BC) patients treated with neoadjuvant chemotherapy (NAC) has received increasing attention. In human epidermal growth factor receptor 2 (HER2)-positive BC, advances in HER2-targeted therapy have not yet clarified the clinical implications of pre-NAC TILs. Likewise, the prognostic role of TILs for long-term survival is not well established.
Methods: Pre- and post-NAC TIL levels were evaluated in 248 pair-matched pre-NAC biopsy and post-NAC resection samples, and analyzed for predictive and prognostic significance with other clinicopathologic parameters. Additional 60 pre-NAC biopsy samples of HER2-positive BC treated with a TCHP regimen (docetaxel, carboplatin, and a combination of trastuzumab and pertuzumab) were also assessed.
Results: High pre-NAC TILs, clinical nodal stage 0-1 (cN0-1), and negative ER expression were shown to be strong predictive markers for pCR. A nomogram based on these significant clinicopathologic predictors was developed, providing integrated probability of achieving pCR after NAC. The association between high pre-NAC TIL levels and significantly increased pCR rate was also confirmed in HER2-positive BC patients treated with a TCHP regimen. After chemotherapy, increased quantity of post-NAC TILs was shown to have extended BC-specific survival and disease-free survival in univariable and multivariable analyses.
Conclusions: High pre-NAC TIL levels were significantly predictive of pCR in BC, and can act as a surrogate marker for predicting therapeutic effects of a TCHP regimen for HER2-positive BC. Post-NAC TILs in residual disease were a new prognostic marker of risk stratification for long-term survival.
Keywords: Neoadjuvant chemotherapy; Nomogram; Pathologic complete response; TCHP; Tumor-infiltrating lymphocytes.