509P - Spatial analysis of tumor-associated macrophages within the tumor microenvironment of primary tumors and matched brain metastases

Background

Novel immunotherapies (IO) show mixed responses, particular in context of brain metastases (BM). We therefore aimed to investigate the density of tumor-associated macrophages (TAM) in primary tumors (PT) and matched BM tissue samples.

Methods

We retrospectively identified patients who received resection of PT and BM between 01/1990 and 10/2022. Immunohistochemical staining and density quantification (positive cells/mm²) of TAMs (CD68⁺ & CD163⁺) was performed. Generated heatmaps were analyzed for heterogeneity as quantified by Shannon Entropy.

Results

We included 62 patients (61.3% male, 38.7% female) with matched samples: 46/62 non-small cell lung cancer, 8/62 breast cancer (BC), 8/62 renal cell carcinoma. Median CD163⁺ TAM density was 733 cells/mm² (range 105-5110 cells/mm²) in BM and 407 cells/mm² (range 52-1786 cells/mm²) in PT. Median CD68⁺ TAM density was 924 cells/mm² (range 119-5521 cells/mm²) in BM and 744 cells/mm² (range 99-2164 cells/mm²) in PT. CD163⁺ TAM density was significantly higher in BM compared to PT over all entities (p<.05). For CD68⁺ TAM, a significant difference was only observed in BC with higher density in BM than in PT (p=.016). Median difference in CD163⁺ TAM density between PT and BM was 163 cells/mm² (range -1258-3602 cells/mm²) and 348 cells/mm² (range -1390-4390 cells/mm²) in CD68⁺ TAM. No correlation between TAM density difference and clinical outcome (time to BM and OS from BM) was observed (p>.05). Median entropy for CD163⁺ TAM in BM was 15.8 (range 1.5-76.2) and 14.3 (range 0.5-45.2) in PT. Concerning CD68⁺ TAM, median entropy was 19.9 (range 1.8-88.7) in BM and 23.9 (range 1.9-54.9) in PT. A significant difference in entropy was only observed in BC as primary breast cancer CD68⁺ TAM showed lower entropy indices (p=.02). Median difference in entropy between PT and BM was 3.4 (range -34.8-41.3) in CD163⁺ TAM and 1.41 (range -34.4-39.9) in CD68⁺ TAM. No correlation of TAM entropy and clinical outcome (time to BM and OS from BM) was observed (p>.05).

Conclusions

TAM density is significantly higher in BM compared to PT. In BC, higher CD68⁺ TAM entropy was observed in BM, indicating higher herterogeneity. Further analyses with enlarged cohort and additional immune cell markers are ongoing.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

The financial support by the Austrian Federal Ministry for Digital and Economic Affairs, the National Foundation for Research, Technology and Development and the Christian Doppler Research Association is gratefully acknowledged.

Disclosure

M. Mair: Other, Travel Support: Pierre Fabre. G. Heller: Other, Personal, Other: X4 Pharmaceuticals. J.N. Kather: Financial Interests, Personal, Invited Speaker: Fresenius, Eisai, MSD; Financial Interests, Personal, Advisory Board: Owkin, DoMore Diagnostics, Panakeia, London, UK. M. Preusser: Financial Interests, Personal, Advisory Board: Bayer, Bristol Myers Squibb, Novartis, Gerson Lehrman, CMC Contrast, GSK, Mundipharma, Roche, BMJ Journals, MedMedia, AstraZeneca, AbbVie, Lilly, Medahead, Daiichi Sankyo, Sanofi, Merck Sharp & Dohme, Tocagen, Adastra, Gan & Lee Pharmaceuticals; Financial Interests, Institutional, Research Grant, Clinical Trials and research: Boehringer Ingelheim, Bristol Meyers Squibb, Roche, Daiichi Sankyo, Merck Sharp & Dohme, Novocure, GSK, AbbVie; Financial Interests, Institutional, Coordinating PI: PharmaMar; Non-Financial Interests, Leadership Role, Brain Tumor Group Chair (current): EORTC; Non-Financial Interests, Leadership Role, EANO Past-President (current): EANO; Non-Financial Interests, Other, Member Multi-Site Guideline Advisory Group: ASCO. A.S. Berghoff: Financial Interests, Personal, Invited Speaker: Roche, Bristol Meyers Squibb, Merck, AstraZeneca; Financial Interests, Personal, Advisory Board: Daiichi Sankyo; Financial Interests, Institutional, Research Grant: Daiichi Sankyo, Roche. All other authors have declared no conflicts of interest.