Breast cancer, DPYD mutations and capecitabine-related ileitis: description of two cases and a review of the literature.

Despite many treatment advances, metastatic breast cancer remains an incurable disease and is the third leading cause of cancer-related deaths in Europe. Capecitabine has become a standard treatment option for metastatic breast cancer, as a single agent or in combination. Hand-foot syndrome and diarrhoea are the most frequently reported side effects, while capecitabine-related ileitis is very rare. Deficiency of dihydropyrimidine dehydrogenase activity leads to severe toxicities after administration of 5-fluorouracil or its prodrugs. We report two cases of patients with metastatic breast cancer who developed ileitis after treatment with capecitabine. One patient had a DPYD gene abnormality.