CMV seropositivity associates with poor clinical outcome in triple negative breast cancer

Cytomegalovirus (CMV) infection modifies immune fitness and T cell subset distribution in healthy donors. We analyzed a recent prospective cohort of 240 patients bearing triple-negative breast cancer for CMV serology status and T cell subsets and assessed recurrence-free survival (RFS) and overall survival (OS). CMV seropositivity was significantly associated with worse RFS (HR = 2.6, 95%CI = 1.2-5.7) and OS (HR = 3.0, 95%CI = 1.2-7.4) in multivariable analyses. A prognostic model incorporating CMV status alongside tumor and nodal stage improved risk stratification. The impact of CMV status was not confirmed in another less well characterized, more ancient cohort (<i>n</i> = 507), probably related to the different therapeutic strategies used in the early 2000s. CMV status had a strong impact on T cell subset distribution with increased frequency of effector CD8 T cells and decreased proportion of Tregs. The impact of CMV infection on cancer patient survival remains to be determined during chemo-immunotherapy, which is now the standard of care.