(767) Codifying the Immune Landscape of Breast Cancer: A Morphology Driven Approach

Introduction/Rationale: Current era in oncology belongs to immunotherapy. Whether it is the increased use of immune checkpoint inhibitors (ICIs) or CAR-T cells or attempts to develop personalized vaccines, different immunotherapies are creating a new order in precision oncotherapy. Current standard immunotherapy use in breast cancer (BC) is restricted to ICIs with chemotherapy in PD-L1 positive TNBC however, in other subtypes research is ongoing. Analysing immunotherapy benefit in BC requires guidelines incorporating novel biomarkers to identify ideal candidates.

Methods: Histomorphology of immune microenvironment of H & E-stained slides of 168 BCs was systematically studied microscopically.

Results: Majority of these demonstrated an immune included (n=131; 77.98%), followed by desert (n=33; 19.64%) and excluded (n=4, 2.38) patterns respectively. In the former type tumour infiltrating lymphocytes were noted in 86.25% however, immunological activity against tumour (apoptosis, nuclear debris etc.) was recognized in 58 (44.27%) cases only [cf. 73 (55.73%) immunologically silent]. Immune cell composition demonstrated predominantly lymphocytes in the majority (n=119; 88.15%) and mixed and predominantly neutrophils in 14 (10.37%) and 2 (1.48%) cases, respectively. Plasma cells were conspicuous in 28/135 (20.74%) of cases. High endothelial venules, considered important for recruitment of immune cells to the tumour were observed in 72.62% (n=123) of Bcs.

Conclusion: Compared to other malignancies BCs are considered as immunologically cold and hence less responsive to immunotherapy however in our cohort majority were immunologically replete albeit with a heterogenous pattern with respect to different immune parameters. The findings warrant thorough investigation of immune landscape of BCs using more sophisticated approaches to recontemplate standalone or combinatorial immunotherapeutic approaches in them.