Incidental detection of raised serum levels of vitamin B12 and its association with neoplasms.

BACKGROUND AND OBJECTIVES: Elevated serum levels of vitamin B12 have been associated with oncohematological diseases. However, the relevance of its incidental detection in subjects without a previous diagnosis of cancer is unknown. The aim of this study was to evaluate the relationship between incidental hypercobalaminemia (vitamin B12 > 1000 pg/mL) and the diagnosis of a tumor process in patients without a diagnosis and to establish the risk factors.

MATERIAL AND METHODS: Retrospective observational study of a cohort of patients with hypercobalaminemia. The incidence of neoplasms was compared with a cohort of patients with vitamin B12 levels <1000 pg/mL.

RESULTS: Vitamin B12 determinations of 4800 subjects were selected. Of them, 345 (7.1%) had levels >1000 pg/mL. 68 (28.4%) were excluded due to exogenous administration, 12 (5%) due to insufficient data and 15 (3%) due to having an active neoplasia, selecting 250 patients, with a median follow-up of 22 (IQR 12-39) months. Structural liver disease was detected in 59 (23.6%). 18.2% (44 patients) had solid organ cancer and 17 (7.1%) had malignant hemopathy. The average time from the detection of hypercobalaminemia to the diagnosis of cancer was about 10 months. The median until the diagnosis of neoplasia was higher in the high vitamin B12 group (13 vs. 51 months p < 0.001). Hypercobalaminemia (HR 11.8; 95% CI 2.8-49.6; p = 0.001) and smoking (HR 4.0; 95% CI, 2.15-7.59; p < 0.001) were independent predictors of neoplasia in the multivariate analysis.

CONCLUSIONS: Incidental detection of serum vitamin B12 levels >1000 pg/mL is high in the population. The diagnosis of solid organ and hematological neoplasia is frequent during the following year of follow-up, with hypercobalaminemia and smoking being predictors of a higher risk of cancer.