Combined Life-Threatening Hematological And Non-Hematological Toxicity In A Patient Treated With Capecitabine For Metastatic Breast Cancer

We report on a patient with metastatic breast cancer, who developed both a life-threatening grade 4 mucositis and a pancytopenia with neutropenic fever during a standard-dosed capecitabine therapy. This case shows the rare possibility of unusually severe 5-fluorouracil (5-FU) typical side effects associated with a normally well tolerated cytostatic treatment. It may well be hypothesized that the adverse effects seen here are due to a hypersensitivity against 5-FU, the terminal effector of capecitabine medication, which is often related to a deficiency of dihydropyrimidine dehydrogenase (DPD).