Association of Circulating T Cell and Tumor Microenvironment Profiles with Immune Checkpoint Blockade Outcomes in Sarcoma

PURPOSE: Immune checkpoint blockade (ICB) benefits only a subset of patients with sarcoma. Biomarkers of response and resistance are needed to help guide patient selection. EXPERIMENTAL DESIGN: We analyzed peripheral blood and tumor samples from patients with sarcoma treated in five ICB-based clinical trials. Baseline peripheral blood mononuclear cells (PBMC) underwent 11-color flow cytometry to define T-cell immunotypes. Baseline tumor tissue underwent RNA sequencing (RNA-seq) to classify tumors into four tumor microenvironment (TME) subtypes using consensus clustering of 29 functional gene expression signatures. Associations between immune features and clinical outcomes were assessed. A deep learning model was applied to baseline hematoxylin and eosin (H&E) slides to detect and quantify lymphoid aggregates in patients with available RNA-seq. RESULTS: Among 178 patients with PBMC available for analysis, a proliferative (PRO) circulating T-cell immunotype was associated with poorer overall survival (OS) than lymphocyte-activation gene 3 (LAG)- or LAG+ immunotypes. RNA-seq from 67 tumors identified an immune-enriched/nonfibrotic TME subtype associated with a higher response rate, longer progression-free survival, and longer OS compared with immune-enriched/fibrotic, immune-depleted, and fibrotic subtypes. Automated analysis of 48 baseline H&E slides identified lymphoid aggregates in five tumors; four were classified as immune-enriched and two of these responded to ICB. CONCLUSIONS: Patients with sarcoma and a PRO circulating T-cell immunotype had inferior outcomes to ICB, whereas those with an immune-enriched/nonfibrotic TME had superior outcomes. Automated analysis of H&E slides showed promise in identifying patients with an immune-enriched TME. These findings support the use of a multimodal approach to identify predictors of response to immunotherapy in sarcoma.