Patients on treatment for indolent lymphoid malignancies, who had anemia [hemoglobin (Hb) 8.5–10.5 g/dL] and functional iron deficiency [transferrin saturation (TSAT) ≤20 %, ferritin >30 ng/mL (women) or >40 ng/mL (men)], were randomized to ferric carboxymaltose (1,000 mg iron) or control. This evidence concerns the gene TF and anemia (phenotype).