Serum vitamin B12 and transcobalamin abnormalities in patients with cancer

One hundred and thirty-nine patients with non-hematologic malignancy were studied to define the incidence of vitamin B12-related abnormalities and correlate them with clinical findings. Based on vitamin B12-binding patterns, the following relatively distinct groups were defined: (A) 50% had normal results; (B) 6% had very high transcobalamin (TC) I and vitamin B12 levels as reported in isolated instances previously: most had hepatic metastases and early death, and all had definite metastatic disease; (C) 11% had high vitamin B12 levels with little or no unsaturated TC I elevation: most also had hepatic and other metastases and early death; (D) 23% had high vitamin B12-binding capacity with normal TC I and vitamin B12 levels: there were no distinguishing features for this group other than an increased proportion of black patients; and (E) 10% had low vitamin B12 levels, in many cases not associated with vitamin B12 deficiency or other known causes of low serum levels. Thus, high serum vitamin B12 level, with or without unsaturated TC I elevation, usually implies a poor prognosis in a patient with cancer. However, while most such patients have hepatic and other metastases, hepatic involvement was not universal nor did most patients with hepatic disease have high vitamin B12 levels. High serum TC I thus is not always due to increased granulocytic proliferation or to hepatic tumor, and alternative mechanisms for TC I accumulation should be sought.