Interstitial pneumonia possibly due to a novel anticancer drug, TS-1: first case report.

A newly approved oral fluoropyrimidine, TS-1, is a dihydropyrimide dehydrogenase (DPD)-inhibiting fluoropyrimidine (DIF) drug. We describe a case of interstitial pneumonia probably caused by TS-1. A peripheral blood lymphocytes stimulating test (DLST) with TS-1 demonstrated a substantial positive reaction. So far only three cases of TS-1-induced interstitial pneumonia have been reported but the relationship between interstitial pneumonia and TS-1 was demonstrated only in this case. Considering that interstitial pneumonia has also been reported with 5-FU, it is necessary in the future to clarify which component of this drug is directly related to interstitial pneumonia.