Vitamin B6 deficiency in cancer patients.

The plasma pyridoxal phosphate concentration was determined in 30 cases of early breast cancer, 21 patients with locally recurrent disease, and 43 patients with systemic metastases. The two groups of advanced breast cancer had significantly lower plasma pyridoxal phosphate levels than 36 healthy women of similar age. Urinary 4-pyridoxic acid excretion was normal in breast cancer. Plasma pyridoxal phosphate concentrations were also reduced in 34 women with widespread cancer derived from primary sites other than breast, but were normal in 39 with early disease.