Tumor-infiltrating lymphocytes, prognosis and trastuzumab benefit in early-stage breast cancer patients from the FinHER trial

The clinical relevance of tumor infiltrating lymphocytes (TILs) in breast cancer (BC) is not firmly established. We aimed to validate previous prognostic findings in triple negative breast cancer (TNBC) and investigate predictive associations with trastuzumab benefit in HER2 overexpressing disease (HER2+). The Finland Herceptin (FinHER) trial (doi.org/10.1186/ISRCTN76560285) was an adjuvant, phase III study enrolling 1010 early-stage BC patients. Those with HER2+ disease (n=232) were randomized to 9 weeks of trastuzumab or no trastuzumab in addition to chemotherapy. Two pathologists independently quantified TILs from the 935 (92.6%) available slides. Distant disease-free survival (DDFS), overall survival (OS), and interactions with trastuzumab were studied. During the FinHER trial, primary breast cancer specimens were collected from women who had undergone mastectomy or breast-conserving surgery and preserved as formalin-fixed paraffin-embedded (FFPE) tissue blocks. RNA extracted from FFPE specimens with Qiagen's miRNeasy FFPE Kit was processed with SensationPlusTM FFPE Amplification and 3'IVT Labeling Kit. Gene expression profiles were derived from the processed RNA using the PrimeView Human Genome U219 Array Plate on the GeneTitanTM instrument.