Anastrozole-induced interstitial lung disease followed by tamoxifen-induced agranulocytosis in a patient with breast cancer.

A 70-year-old woman with the breast cancer exhibited interstitial lung disease 20 months after the administration with anastrozole, which was performed as the post-operative adjuvant therapy. The drug-induced lymphocyte stimulation test revealed that anastrozole was responsible for the development of interstitial lung disease in this patient. The interstitial lung disease was effectively treated by prednisolone. Then, tamoxifen was used as an alternative therapy, resulting in the occurrence of agranulocytosis 24 days after the administration with tamoxifen. Both anastrozole and tamoxifen are widely used and are highly effective drugs for the treatment of breast cancer. However, the current patient shows that both drugs could cause, albeit very rare, serious side effects in some patients.