Abstract P1-07-03: Evaluation of the prognostic value of CD3, CD8 and FOXP3 mRNA expression in early breast cancer patients treated with anthracycline-based adjuvant chemotherapy

Background: Tumor-infiltrating lymphocytes (TILs) have been shown to be of prognostic value in several cancer types. In early breast cancer, TILs have a prognostic utility, as well, especially in HER2-positive and triple-negative breast cancer (TNBC). TILs presence is broadly associated with improved survival, however there is controversy regarding TILs subpopulations. In general, T cell infiltration is higher in non-luminal and more aggressive tumors, like the basal-like subtype. Among TILs subpopulations, CD8-positive T cell infiltration is associated with better outcome, whereas high numbers of FOXP3-positive T regulatory cells are associated with worse outcome in ER-positive tumors and better outcome in HER2-positive and TNBC tumors.

Patients and Methods: Early breast cancer patients, treated with anthracycline-based chemotherapy within two randomized trials (HE10/97 and HE10/00) were included in the study. We evaluated, by qRT-PCR, 826 macrodissected formalin-fixed paraffin-embedded tumor tissue samples for mRNA expression of CD3, CD8 and FOXP3for potential prognostic significance in terms of disease-free survival (DFS) and overall survival (OS). TILs were evaluated in whole sections as percent of total cells.

Results: Median age was 52.7 years, while 54.2% of the patients were postmenopausal and 79.0% ER/PgR-positive. After a median follow-up of 133.0 months, 255 patients (30.9%) had died and 314 (38.0%) had disease progression. All three mRNA markers were positively correlated with TILs (Spearman's r=0.52 for CD3, 0.41 for CD8 and 0.47 for FOXP3, all p-values <0.001), while Ki67 protein expression was greater in tumors with high mRNA expression (median cut-off) of the markers (Mann-Whitney, all p-values <0.001). Additionally, tumors of higher histological grade and negative ER/PgR status were more frequent in patients with high CD3, CD8 or FOXP3 mRNA expression, as compared to patients with low expression, (chi-square, p-values <0.010). In the univariate analysis, high CD3 and CD8 mRNA expression was found to be of favorable prognostic value for DFS (HR=0.74, 95% CI 0.59-0.92, Wald's p=0.007 and HR=0.76, 95% CI 0.61-0.95, p=0.016, respectively). In multivariate analyses, the association of high CD8 mRNA expression with increased DFS was retained (HR=0.77, 95% CI 0.60-0.99, p=0.048), whereas that of high CD3 mRNA expression was of marginal statistical significance (HR=0.77, 95% CI 0.59-1.01, p=0.059). Moreover, a significant interaction was observed between HER2 status and CD3 mRNA expression with respect to DFS (interaction p=0.032). In the HER2-positive subgroup, the hazard ratio associated with high CD3 mRNA expression was of greater magnitude (HR=0.48, 95% CI 0.30-0.76, p=0.002) compared to the hazard ratio presented above, for the entire cohort. No significant findings were observed for FOXP3 in terms of DFS, while none of the studied markers were of prognostic value for OS.

Conclusions: High CD3 and CD8 mRNA expression in early breast cancer patients is of prognostic value for decreased risk for relapse and, in the future, could potentially be of importance in deciding the most appropriate therapeutic strategy in light of the recent immune-related treatment developments.

Citation Format: Tsiatas M, Kalogeras KT, Manousou K, Wirtz RM, Gogas H, Veltrup E, Zagouri F, Lazaridis G, Koutras A, Christodoulou C, Pentheroudakis G, Petraki C, Bafaloukos D, Pectasides D, Kosmidis P, Samantas E, Karanikiotis C, Papakostas P, Dimopoulos M-A, Fountzilas G. Evaluation of the prognostic value of CD3, CD8 and FOXP3 mRNA expression in early breast cancer patients treated with anthracycline-based adjuvant chemotherapy [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-07-03.