B cells (CD20+) associated to tumor infiltrating cytotoxic T-cells observed on resected liver colorectal metastases (LCM) are prognostic

Abstract

Aim: Colorectal cancer infiltrating cytotoxic T-cells (CD8+ cells) are a strong prognostic factor for survival after primary tumor and metastases resection. The impact of B cells for prognosis is less characterized. Methods: Metastatic colorectal patients (pts) engaged for curative liver surgery with available FFPE blocks for all resected LCM, were included. The density of CD8+ and CD20+ cells in the metastasis (CT) and the invasive margin (IM) for all LCM was determined by whole-slide immunohistochemistry and quantified with dedicated image analysis software. The mean value of the 3 most infiltrated areas (0.8 mm2) was calculated. The densities of CD8 and CD20 (CT and IM regions) were classified into Hi or Lo according to cut-off values (minimal p-value approach). The total number of Hi densities was calculated to determine the immunoscore (IS) 0-2 Hi (low IS) or 3-4 Hi (high IS). For pts with multiple LCM, all LCM were quantified. The mean value of all densities, the least and the most infiltrated LCM/pt were analyzed. Cumulative DFS/OS analyses were performed using the Kaplan-Meier estimator. The hazard ratio (HR) for OS/DFS comparing (IS0-2 vs 3-4) was determined using univariate Cox regression and the significance by log-rank tests. Results: 294 LCM from 88 patients (M/F 1.1, mean 3.3/pt, synchr/metachr 5.8) were included. For the least infiltrated metastasis: a high IS is prognostic for DFS and OS. Independently of CD8 cells, a high CD20 density associated concomitantly with both regions (CT/IM) is prognostic for OS (HR: 0.36; p = 0.00004) but not for DFS (HR 0.58, p = 0.1). [...