Background: Elevated plasma vitamin B12 levels (cobalamin, Cbl) are associated with increased short-term cancer risk among patients referred for this laboratory measurement. We aimed to assess prognosis in cancer patients with elevated plasma Cbl.
Methods: We conducted a population-based cohort study using data from Danish medical registries during 1998-2014. The study included 25,017 patients with a cancer diagnosis and Cbl levels of 200-600 pmol/L (reference/normal range), 601-800 pmol/L and >800 pmol/L measured up to one year prior to diagnosis, and a comparison cohort of 61,988 cancer patients without a plasma Cbl measurement. Patients treated with Cbl were excluded. Survival probability was assessed using Kaplan-Meier curves. Mortality risk ratios (MRR) were computed using Cox proportional hazard regression, adjusted for age, sex, calendar year, cancer stage and comorbidity, scored using the Charlson comorbidity index.
Results: Survival probabilities were lower among patients with elevated Cbl levels than among patients with normal levels and among members of the comparison cohort [(1-year survival,%) Cbl: 200-600 pmol/L: 69.3%; 601-800 pmol/L: 49.6%; >800 pmol/L: 35.8%; comparison cohort: 72.6%]. Thirty-day mortality was elevated for patients with Cbl levels of 601-800 pmol/L or >800 pmol/L, compared to patients with levels of 200-600 pmol/L [(MRR (95% confidence interval): 601-800 pmol/L vs. 200-600 pmol/L: 1.9 (1.6-2.2); >800 pmol/L vs. 200-600 pmol/L: 2.7 (2.4-3.1)]. This association remained robust for 31-90-day and 91-365-day mortality, showing similar dose-response patterns.
Conclusion: Cancer patients with elevated Cbl levels had higher mortality than those with normal Cbl levels. These findings may have clinical significance for assessing the prognosis of cancer patients.
Keywords: Cancer; Cohort studies; Epidemiology; Mortality; Registries; Vitamin B 12.
Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.