Interstitial pneumonitis induced by bicalutamide given for prostate cancer

We describe interstitial pneumonitis induced by bicalutamide prescribed to treat prostate cancer. A 78-year-old man with severe lower paralysis and a bladder/rectal disorder was referred to our hospital. Prostate-specific antigen was elevated to 1418 ng/mL at that time and magnetic resonance imaging revealed multiple bone metastases. A rectal examination revealed hard nodules in the bilateral lobes of the prostate. We diagnosed prostate cancer without a biopsy, and then maximally blockaded androgens by castration and bicalutamide administration. Eight months later, he was admitted to a local hospital with breathing difficulties, and a computed tomography scan revealed interstitial pneumonitis. A physician concluded that the cause of the interstitial pneumonitis was bicalutamide, which was immediately withdrawn and replaced with prednisolone. The patient recovered over a period of 3 months. Bicalutamide-induced interstitial pneumonitis is quite rare. However, adverse reactions to maximal androgen blockade therapy should be considered and appropriate treatment for interstitial pneumonitis should be promptly initiated, as this condition is reversible.