Bone Marrow CD8+ Cytotoxic T-lymphocyte Subset: A Prognostic Indicator in Acute Myeloid Leukemia.

Acute myeloid leukemia (AML) is a heterogeneous disorder with variable clinical outcomes due to the complex molecular and cytogenetic basis of the disease. In light of recent developments in immunotherapy, bone marrow (BM) microenvironment immune composition, including baseline lymphocyte subset profiles, may be relevant for understanding host-tumor immunologic interactions. We conducted a study on 88 newly diagnosed AML patients to evaluate the baseline BM CD8⁺/CD3⁺ cytotoxic T-lymphocyte (CTL) subset by flow cytometry and its relation to standard prognostic factors, response to induction therapy, and disease outcome. Our results showed that a higher percentage of BM CD8⁺/CD3⁺ CTLs (≥10%) was associated with significantly better overall survival (P = 0.020) and progression-free survival (P = 0.020) compared with cases with <10%. Moreover, a lower BM CD8⁺/CD3⁺ CTL percentage was associated with adverse prognostic parameters, including higher total leukocyte count (r = -0.512, P < 0.001) and higher blast counts in both BM (r = -0.290, P = 0.006) and peripheral blood (r = -0.364, P < 0.001). These findings suggest an important role of this subset in the antitumor immune response. Large-scale studies are warranted to confirm these results and further clarify the role of BM CTLs as a prognostic indicator and predictor of survival in AML.