Background: Vitamin B12 deficiency is a common long-term sequelae after total gastrectomy. Intramuscular injection of vitamin B12 is the only known treatment. We investigated the efficacy and safety of oral vitamin B12 replacement for gastric cancer patients with vitamin B12 deficiency after total gastrectomy. Methods: We performed a single-arm, open-label, fixed-drug dosage, prospective study (NCT00699478) involving gastric cancer patients who underwent total gastrectomy. Vitamin B12-deficient (<200 pg/ml) patients (n = 30) received daily oral vitamin B12 (dosage: 1500 μg mecobalamin) administration for 3 months. The primary outcome measurement was serum vitamin B12. The secondary outcome measurements were improvement of neurologic symptoms and hematologic findings (serum folate, homocysteine, ferritin, iron, total iron binding capacity, transferrin, and mean corpuscular volume). For comparison, another group of vitamin B12 deficient patients (n = 30) received intramuscular vitamin B12 injections (dosage: 1000 μg cyanocobalamin) weekly for 5 weeks and monthly thereafter for a total of 3 months in a separate study period. Results: In both groups, mean serum vitamin B12 increased after 30 days of treatment and was maintained up to 90 days. No adverse effects related to oral or intramuscular vitamin B12 replacements were noted. Both groups showed decreased homocysteine levels. Before treatment, 29 patients in the oral vitamin B12 group had neurologic symptoms related to vitamin B12 deficiency. After oral vitamin B12 treatment, 28 patients experienced symptom relief, and 16 patients were symptom free. Conclusions: Oral vitamin B12 replacement is an effective and safe treatment for vitamin B12 deficiency in gastric cancer patients after total gastrectomy.
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