Thiamine deficiency as a possible cofactor causing cognitive dysfunction in a patient with end-stage gastric cancer .

We describe a case of a patient treated for cognitive dysfunction (CD) with suspected thiamine deficiency (TD). A 74-year-old man with gastric cancer presented with grade 3 diarrhea and grade 1 anorexia. He had been receiving trastuzumab plus tegafur (a chemotherapeutic fluorouracil prodrug), gimeracil, and oteracil (S-1) and oxaliplatin. On admission, cognitive function was assessed with the Hasegawa's Dementia Scale (HDS-R) because he had impaired short-term memory. His thiamine levels increased from 22 to 109 ng/mL after administration of 75 mg of thiamine. Furthermore, the patient's HDS-R score improved from 9 to 22, and cognitive and memory functions improved. TD should be considered in older CD patients receiving oral chemotherapy agents including fluorouracil.