Correlation of clinical and pathological features with the tumour microenvironment in DCIS: An institutional experience

Background The predictors of recurrence in ER- DCIS and the role of tumor microenvironment (TME) is unclear. Correlation of clinico-pathologic features of ER- DCIS with molecular markers and PD-L1 expression has not been done. Therefore, we under took this retrospective study comparing the clinical outcomes between ER+ and ER- DCIS and correlated this with the expression of PD-L1 in the tumor cells and the Tumor infiltrating lymphocytes. We hypothesize that increased expression of PD-L1 in ER- DCIS and TILs predict recurrence. The aim of this study was to identify biomarkers in ER- DCIS associated with increased risk of recurrence or progression to metastatic disease. Methods 50 patients with ER+ and ER- DCIS were identified retrospectively. Clinico-pathologic data was correlated with survival outcomes and local or distant recurrence. Information collected was the size, margin status, nuclear grade, ki-67 expression, architectural pattern, necrosis, and molecular phenotype. 25 cases of ER- DCIS are presented in the abstract. The rest will be presented at the meeting. ER+ and ER- DCIS will be stained for PD-L1, and lymphocyte markers CD3, CD4, CD8, FoxP3, and CD20 for the TILs in ER+ and ER- DCIS. The clinical, radiological and Immuno-pathologic features of ER+ DCIS will be compared with ER negative DCIS. Results 3/25 (12%) had disease recurrence. Two (67%) had recurrence with metastatic triple negative breast cancer with brain, hepatic and osseous metastasis within 5 years. High grade was associated with the development of systemic disease. 1/3 (33%) had recurrence as ER negative DCIS. 2/3 (67%) had recurrence as ER+ tumor. The rate of recurrence and distant metastasis was seen to be higher in high grade ER negative DCIS. Conclusions ER- DCIS has an aggressive phenotype and a distinct biology. It is more likely to present as loco-regional or metastatic disease. Identification of genomic biomarkers, PD-L1 analysis in the tumor and the TILs is currently being undertaken. The molecular drivers and immunologic markers of recurrence in ER negative DCIS continue to be an active area of exploration. Further characterization of ER- DCIS immune microenvironment may identify useful targets for immune-based therapy and breast cancer prevention. Legal entity responsible for the study The authors. Funding Has not received any funding. Disclosure All authors have declared no conflicts of interest.