[DLST as a method for detecting TS-1-induced allergy].

Drug-induced allergic adverse events including rash, interstitial pneumonia and hepatic injury are often observed in a few patients treated with anticancer drugs that are 5-FU derivatives, including TS-1. In patients suspected to be liable to develop allergic reactions, the drug-induced lymphocyte stimulation test (DLST), based on the (3)H-thymidine incorporation ratio into the DNA of lymphocytes derived from the patients, is generally employed to identify drugs that could induce allergy. In this case report, we conducted the DLST on 20 healthy volunteers without TS-1 treatment in order to obtain reference data on the evaluation of TS-1-induced allergy. Even though all 20 volunteers were healthy, there were 6 positive responses to the DLST. In view of the positive response to TS-1 in healthy volunteers undergoing the DLST, it is suggested that the DLST could show a false positive response through an intracellular function that accelerates incorporation of thymidine in the lymphocytes by the salvage pathway after inhibition of DNA de novo synthesis caused by 5-FU derivative anticancer, including TS-1. Therefore, such a positive response to the drugs is considered, in fact, to be false-positive in the DLST. In view of the occurrence of false-positive results, the possibility of drug-induced allergy in patients receiving TS-1 should be carefully evaluated using a combination of other clinical examinations.