TMIC-03. TUMOR INFILTRATING LYMPHOCYTES IN BRAIN METASTASIS: CLINICOPATHOLOGICAL EVALUATION AND COMPARISON WITH PAIRED PRIMARY

Abstract INTRODUCTION Little is known about tumour-infiltrating lymphocytes (TILs) in brain metastasis (BM) and their utility as predictive biomarker for immunotherapy. AIM: To analyze TILs BM, correlate with corresponding paired primary (PP). METHODS Inclusion: Histologically confirmed BM PP (2015-2020). Exclusion: Hematological malignancies, spinal cord/meningeal metastasis, pediatric age, slides/blocks not available. Final Nf 277 BM; 64 PP. One H&E slide from both &BM assessed stromal (sTILs) intratumoral (iTILs) per International TIL Working Group guidelines. RESULTS Median sTILs (10%) were significantly higher than iTILs (1%) (p-value < 0.001). mild (<10%) majority of (57.8%) (59.9%), while nearly always (primary 97.1%; 96.9%). Between no change sTIL category 48.43%, conversion 51.56%, to lower (66.67%) > (33.33%). Conversion rate breast (54.3%) &GIT (62.5%) lung (45.5%) &GUT (40%). In preoperative steroid therapy (PST) showed (≤10%) (p-value= 0.041), adenocarcinoma histology ( >10%) 0.001), precocious 0.051) absence extracranial 0.083) trended towards sTILs. survival whole cohort was 20 months (95% CI 14.4-25.68 months). Presence 0.01); 0.007) overall (OS), better OS 0.029), univariate multivariate analysis. Absence PST longer median survival, though significant (24.1 vs 19.8months; p-value= 0.19). CONCLUSIONS predominantly show high >low between signifying lowered immune response BM. Thus, evaluation wherever tissue available, may be indicated if immunotherapy considered. Parameters possibly indicating prognostic role tumor microenvironment