Abstract P4-04-17: Tumor-infiltrating neutrophils in breast cancer subtypes: A retrospective cohort study

Abstract

Abstract Background: Tumor infiltrating neutrophils (TINs) are related to aggressiveness and poor prognosis in several human cancers. Despite evidence pointing towards the pivotal role of inflammatory cells in the initiation, progression and response to treatment of breast cancer (BC), the relevance of TINs in BC has not been systematically investigated. We sought to determine if TINs were present in BC and to compare their presence among different subtypes. We hypothesized that the presence of TINs would correlate with more aggressive histologic subtypes, particularly triple negative (TN) tumors. Methods: This retrospective cohort study analyzed patients with BC treated at our institution from 2006 to 2012. Women with treatment-naïve stage I-III BC and with available medical records were included. Those with metastatic disease and/or lacking material for pathologic review were excluded from analysis. Tumors were divided into three subtypes: luminal type (LT) (hormone-receptor[HR]-positive, HER2-negative); HER2-positive and TN. Clinical and pathological characteristics were recorded. The primary outcome was the amount of TINs, defined as neutrophils in direct contact with tumor cells, within each tumor. Hematoxylin & eosin stained sections were examined by a dedicated breast pathologist blinded to tumor subtype, and the number of TINs per 10 high power fields (HPF, 40x) was recorded. To evaluate the capacity of TIN measurements in predicting HER2+ or TN tumors and to identify an optimal cut-off value for TIN positivity, ROC curve analysis was performed. Fisher’s exact test was used to test for independence between qualitative variables, and logistic regression models were used for quantitative variables and multivariate analysis. Results: 133 patients were assessed for inclusion. 28 were excluded because of missing material, incorrect staging or erroneous pathological diagnosis and 105 were analyzed. 72 tumors (69%) were classified as LT, 15 (14%) as HER2+ and 18 (17%) as TN. The mean TIN count was 1.82 x 10 HPF (0-28). ROC analysis determined a cut-off value for positivity of >1 TIN x 10 HPF (AUC 0.85; 95% CI 0.76-0.93, p<0,001). Tumors with >1 TIN x 10 HPF were considered TIN-positive. 27% of all tumors were TIN+ (n=28). 16 of 18 TN (88%), 8 of 15 HER2+ (53%) and 4 of 68 LT tumors (5%) were TIN+ (p<0.001). 79% of HR-ve tumors (19 of 24) were TIN+, in contrast with 11% of HR+ve (9 of 81) (p<0.001). HER2 expression (p=0.023); tumor grade (p<0.001) and Ki67 (p<0.001) were also associated with TIN positivity. Age, menopausal status and T and N stage were not significant for the presence of TINs. On multivariate analysis, only Ki67 (OR 1.05, 95% CI 1.01-1.1, p=0.008) and HR negativity (OR 10.6; 95% CI 2.5-45.8, p=0.002) were associated with a higher likelihood of TIN positivity. Conclusions: Although TINs are uncommon in BC, they are present in most TN and in half of HER2+ tumors. In fact, the absence of HR expression was the strongest predictor for TIN positivity. These results raise the question as to whether TINs, as part of the tumor microenvironment, have a role in the aggressiveness and progression of TN tumors and warrant further investigation of TINs in this BC subtype, particularly in relation with response to treatment and prognosis. Citation Format: Enrique Soto-Perez-de-Celis, Mariana A Tenorio-Serralta, Yanin Chavarri-Guerra, Eucario Leon-Rodriguez, Armando Gamboa-Domínguez. Tumor-infiltrating neutrophils in breast cancer subtypes: A retrospective cohort study [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P4-04-17.