CD4 and cancer: Studies performed by our group and others, including over 3,000 patients with advanced cancers, have shown that regardless of the histological subtype and treatment, global and CD4+ lymphopenia are powerful independent predictors of risk of high grade toxicity associated with chemotherapy including febrile neutropenia (FN) [59, 64, 66, 67], severe thrombocytopenia requiring platelet transfusion [60], severe anemia requiring red blood cells (RBC) transfusion [61, 62] and increased risk of early death after chemotherapy [19–21, 63].