MSR1 and neoplasm: Tumor CD204+ macrophage infiltrate density increased in dogs receiving SBRT only (mean density: 7.57% pre-treatment vs. 8.79% post-treatment, fold change: 1.51), whereas the density decreased in tumors from animals that received SBRT + immunotherapy (mean density: 24.2% pre-treatment vs. 14.75% post-treatment, fold change: 0.50); the fold change in macrophage density was not significantly different between the treatment groups (p = 0.151) (Figure 1).