The Vitamin B12–C-Reactive Protein Index in Advanced Cancer: A Case Report and Narrative Review of an Underutilized Potential Prognostic Biomarker

Abstract

Identifying simple, accessible, and reproducible biomarkers that can improve the prognostic assessment of patients with advanced cancer is a major challenge in palliative medicine. The association between vitamin B12 hypervitaminemia and an inflammatory syndrome, as evidenced by elevated C-reactive protein (CRP) levels, could serve as a complementary prognostic biomarker in patients with advanced cancer. Clinical, imaging, and laboratory findings from the reported patient were reviewed. The B12–CRP index (BCI) was calculated as serum vitamin B12 in pmol/L multiplied by CRP in mg/L. Published evidence on elevated vitamin B12, inflammation, and prognostic assessment in advanced cancer was discussed narratively. We report the case of a 64-year-old man with poorly differentiated cholangiocarcinoma diagnosed 5 months prior, treated with gemcitabine-cisplatin in combination with durvalumab. Despite this treatment, a follow-up computed tomography scan revealed major tumor progression with hepatic metastases, portal vein invasion, the development of peritoneal carcinomatosis, and pulmonary nodules. The clinical examination revealed a significant deterioration in the patient’s general condition, with a Palliative Performance Scale version 2 (PPSv2) score of 50%. Laboratory results showed hypervitaminemia B12 at 1,126 pmol/L, CRP at 16.8 mg/L, hypoalbuminemia at 30 g/L, significant cholestasis, moderate cytolysis, and hypercalcemia. The BCI was 18,917. Palliative care was required. The BCI could serve as a potential complementary prognostic biomarker to enhance the prognostic assessment of patients with advanced cancer. Prospective studies are nevertheless needed to clarify its role in decision-making strategies in palliative medicine.