This 2016 cross-sectional study evaluated the effectiveness of methylmalonic acid (MMA) and homocysteine (HC) as biomarkers for vitamin B-12 deficiency in 316 cancer patients. Despite normal or elevated serum B-12 levels, 8.9% of patients were deficient based on B-12 (260 nmol/L), and 17.4% based on HC (>12 μmol/L). Weak negative
