A case of suspected S-1 induced interstitial pneumonia.

A 37-year-old female with advanced gastric cancer and liver metastases was treated with S-1. Since the patient noticed a transient cough and low-grade fever in the middle of the third course of treatment, administration of S-1 was discontinued. Her symptoms resolved in three days, and the fourth course was started again. However, two weeks later she was hospitalized with non-productive coughing, and exertional dyspnea with severe hypoxemia. CT scan showed minimal ground glass shadow in bilateral lungs and that the multiple liver metastases were strikingly reduced in size. CT scan obtained on the third hospital day showed extensive ground glass and consolidative changes in bilateral lungs. She died on the same day despite high-dose steroid therapy. Although a definite causal relationship between pneumonia and S-1 is still unproven, S-1-induced pneumonia needs to be considered in the differential diagnosis when patients present with dyspnea are treated with S-1.