A 67-year-old male presents with increasing fatigue and is found to be anemic. Physical examination reveals a hard 1-cm nodule in the left lobe of the prostate. The prostatic-specific antigen (PSA) level is found to be elevated. Examination of the peripheral blood reveals an occasional myelocyte. The erythrocytes are mainly normochromic and normocytic, and teardrop RBCs are not found. There are however, about two nucleated red blood cells per 100 white cells. What is the best diagnosis for this patient's anemia?