Abstract P1-08-26: Morphologic characterization of tumor-infiltrating lymphocytes and its relation with pathological response in a series of breast cancer patients treated with primary chemotherapy

Abstract

Abstract Introduction: Tumor-Infiltrating Lymphocytes (TILS) is a well-known predictor of response to primary chemotherapy1,2 and a prognostic factor for improved survival in different breast cancer subtypes3. We present data on the association of the level of TILs and morphologic characteristics of such infiltrate with pCR. Material and methods: A series of 477 breast cancer patients (479 tumors) treated with primary chemotherapy at Catalan Institut of Oncolgy - H.U. Bellvitge between January 2009 and December 2016. Chemotherapy consisted on anthracyclines and taxanes (plus trastuzumab if Her-2 positive disease). Levels of percentage of TILs using hematoxylin-eosin-stained sections of diagnostic core-needle biopsy were evaluated according to international guidelines in a prospectively defined retrospective analysis. Characterization of TILS consisted on identification of plasma cells, intraepithelial infiltrate vs stromal infiltrate and homogeneous vs heterogeneous infiltrate. A sub-classification using levels of TILS and heterogeneity was done for statistical purposes. Levels of TILS and their morphological characteristics were examined for their associations with pCR adjusted for predictive clinic-pathological factors, by univariate and multivariate logistic regression, statistical significance set at 0.05. A ROC curve was performed to look for a cut-point of TILs to predict PCR. Results: The mean value of TILs was 23.79% (SD, 24%). TILs were significantly higher in ductal carcinomas (39.1% vs 0%, p=0.007), grade 3 (55.2 vs 17.7%p<0.001), ki 67 >30 (48.8% vs 24.5%, p<0.001), HER2 (56.6%) and triple negative tumors (TNBC)(56.6%) vs luminal (20%), p<0.001). The level of TILS was set in 20% to predict pCR by a ROC curve (S=62.3% E=71%). Characterization of TILs found plasma cells in 41.1% of the samples, intraepithelial infiltrate in 11.2% and homogeneous infiltrate in 60.1%. Homogeneously high infiltrate was found in 20% of the samples. In the univariate analysis pCR was higher in samples with TILs > 20% (15.2% vs 41.5%, OR: 3.96 [95%CI, 2.57-6.10]; P < 0.001); plasma cells (OR 6.61 [95%CI, 1.51-28.8]; P=0.01), intraepithelial TILS (OR: 10.34 [95%CI, 2.22-48.01]; P =0.003), homogeneous high infiltrate (OR: 13.6 [95%CI, 3.04-60.77]; P =0.001). In luminal tumors, TILs over 20% predicted pCR (OR 12.3 [95%CI, 4.0-37.7]; P < 0.001) as well as in TNBC (OR 4.32 [95%CI, 1.77-10.53]; P=0 .001) but not in those cases with HER2 positive tumors (luminalB HER2 + HER2) (OR 1.65 [95%CI, 0.88-3.07]; P=0.118). In the multivariate analyses, levels of TILs > 20% were associated with higher pCR rates (adjusted odds ratio, 2.44 [95%CI, 1.48-4.01]; P < .001). Conclusions: The presence of TILs over 20% at diagnosis is an independent, positive, predictive marker of pCR in early breast cancer treated with neoadjuvant chemotherapy. Interestingly, the predictive information added by TILs >20% was higher in luminal and triple negative tumors compared to HER2 positive cases. Careful morphological characterization of TILS may add valuable predictive information and can be done in current pathologic laboratories with a well-trained breast cancer pathologist.