Vitamin B12 Deficiency in Patients with Chronic Myeloid Leukemia

Abstract

High vitamin B12 (cobalamin) levels have been documented in patients with untreated chronic myeloid leukemia. However, the literature about vitamin B12 deficiency in patients with chronic myeloid leukemia who are receiving imatinib is scarce. The objective of this study was to investigate the prevalence of vitamin B12 deficiency in patients with chronic myeloid leukemia. We retrospectively reviewed the medical records of 195 patients with chronic myeloid leukemia seen in the outpatient clinic of our institution between 2006 and 2007. The median age of patients was 35 (range 9 – 77); 118 (60%) patients were males and 77 (40%) were females. All patients included in the study were receiving imatinib. Macrocytic anemia at any given time during the course of treatment was documented in 61 (31%) out of 195 patients. Serum vitamin B12 and folate levels were measured in all patients with macrocytic anemia using chemiluminescent enzyme immunoassay. Among these 61 patients, 33 (54%) had low vitamin B12 levels (< 200 pg/ml), 12 (20%) had indeterminate levels (200 – 300 pg/ml) and 16 (26%) patients had levels > 300 pg/ml. Folate levels were within normal range (3 – 17 ng/ml) in all but two patients and both of these patients had folate levels < 3 ng/ml and vitamin B12 levels > 300 pg/ml. Among 195 study patients, 33 (17%) had macrocytic anemia with low vitamin B12 levels and 12 (6%) had macrocytic anemia with indeterminate vitamin B12 levels. We conclude that vitamin B12 deficiency is prevalent in our patients with chronic myeloid leukemia who are taking imatinib. This is of significance because our patient population is non-vegetarian. Serum vitamin B12 should be measured as a part of work up for anemia in patients with chronic myeloid leukemia. Correction of vitamin B12 deficiency in these patients could improve their tolerance to imatinib, which potentially is a myelosuppressive drug. In our study, measurements of serum methylmalonic acid (MMA) and homocysteine levels in patients with indeterminate vitamin B12 levels were not performed; although these measurements could have confirmed the diagnosis of vitamin B12 deficiency in this subgroup. We suggest that a similar study be conducted in a different patient population elsewhere.