CD103 and Intratumoral Immune Response in Breast Cancer

Purpose: CD103 is expressed in several immune cell types but in the context of the intratumoral immune response may be most important as a marker of antigen-activated CD8 T cells. Methods: We have examined the prognostic significance of CD103 TILs in breast cancer by IHC in a cohort of 424 breast cancer patients. Results: CD103 TILs were present in all subtypes but were more abundant in ER-negative tumors where CD103 TILs were preferentially localized to the intraepithelial compartment. CD103 was associated with tumor size, tumor grade, and ER/PR status (P < 0.05). CD103 TIL density and the epithelial to stromal ratio was highest in the basal-like tumors. Intraepithelial CD103 but not intrastromal CD103 was associated with better relapse-free and overall survival in basal-like subtype tumors [HR = 0.28; 95% confidence interval (CI), 0.17–0.72; P = 0.0047 and HR = 0.25; 95% CI, 0.17–0.66; P = 0.0017, respectively). CD8 status showed similar but less significant associations, but the combination of dual CD103+CD8+ TIL status was the most strongly prognostic combination for relapse-free and overall survival (HR = 0.10; 95% CI, 0.07–0.62; P = 0.006 and HR = 0.09; 95% CI, 0.07–0.57; P = 0.003, respectively). Conclusions: CD103 TILs are indicative of a good prognosis specifically within the basal-like subtype of breast cancer. Clin Cancer Res; 22(24); 6290–7.