Abstract B29: CD163-positive tumor-associated macrophages and CD8-positive cytotoxic lymphocytes are powerful diagnostic markers for therapeutic stratification of osteosarcoma patients in the French OS 2006 trial

The French phase 3 trial (OS 2006) testing combining zoledronate (an osteoclast inhibitor) with chemotherapy and surgery did not improve the outcome of patients with osteosarcoma. To understand this unexpected result, the presence of infiltrating immune cells was investigated in 124 biopsies of patients enrolled in the trial. The percentage of CD68/CD163 tumor-infiltrating macrophages, CD8 lymphocytes, osteoclasts, and the PD1/PDL-1 checkpoint was assessed by immunohistochemistry. M1/M2 macrophage polarization was characterized by pSTAT1/CMAF staining. The expression of these biomarkers was correlated with clinical outcome. No statistical correlations were found with response to chemotherapy. High CD163 levels (u003e50% of cells per core; 43.8% of patients) were associated with CMAF nuclear expression and significantly correlated with greater overall survival (p=0.0025) and with longer metastasis progression-free survival (MPFS, p=0.0315) independently of diagnosis status (p=0.002). Only a trend was observed for patients with high CD68-positive cells (p=0.0582). CD8 staining was positive in u003e50% of cases with a median staining of 1%. Lower CD8 levels were associated with metastatic disease at diagnosis and only the presence of CD8-positive cells significantly correlated with improved overall survival in zoledronate-treated patients (p=0.0415). PD1/PDL-1 staining was negative in u003e80% of cases and was not correlated to prognosis. Finally, CD163-positive TAMs and CD8-positive cells (and not the PD1/PDL-1 checkpoint) are crucial predictive biomarkers in osteosarcoma. For the first time, we described a correlation between CD8-positive cells and zometa treatment. The immunohistochemical analysis of the microenvironment in osteosarcoma patient biopsies could represent a novel tool for therapeutic stratification. Citation Format: Anne Gomez-Brouchet, Claire Illac, Julia Gilhodes, Corinne Bouvier, Sebastien Aubert, Jean-Marc Guinebretiere, Beatrice Marie, Frederique Larousserie, Natacha Entz-Werle, Gonzague de Pinieux, Thomas Filleron, Veronique Minard, Vincent Minville, Eric Mascard, Francois Gouin, Marta Jimenez, Marie-Cecile Ledeley, Sophie Piperno-Neumann, Laurence Brugieres, Francoise Redini. CD163-positive tumor-associated macrophages and CD8-positive cytotoxic lymphocytes are powerful diagnostic markers for therapeutic stratification of osteosarcoma patients in the French OS 2006 trial [abstract]. In: Proceedings of the AACR Conference on Advances in Sarcomas: From Basic Science to Clinical Translation; May 16-19, 2017; Philadelphia, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(2_Suppl):Abstract nr B29.