Questions 1 and 2 refer to the following case:
A 55-year-old woman presents with progressive fatigue over the past few months. Her past medical history is significant for breast cancer stage IIA diagnosed 5 years ago. Her treatment consisted of mastectomy and locoregional radiation, followed by chemotherapy with adriamycin and cyclophosphamide. On exam, pallor and some bruising on her arms are noted. There is no palpable lymphadenopathy, and the liver and spleen are not palpable. Complete blood count (CBC) shows a white blood cell (WBC) count of 1500/μL, 60% neutrophils, 24% lymphocytes, 12% monocytes, 0% basophils, 2% eosinophils, hemoglobin of 7.5 g/dL, and a platelet count of 80 × 10³/μL. The mean corpuscular volume (MCV) is 110 µm³. Other laboratory test results include creatinine 0.8 mg/dL, alanine aminotransferase (ALT) 24 U/L, and aspartate aminotransferase (AST) 20 U/L; levels of B12, folate, and thyrotropin are normal. Erythropoietin level is 36 IU/L.