Flutamide is associated with liver toxicity. I'm assuming your doctor checks liver enzymes regularly. Bicalutamide, relative to flutamide, appears to be safer.
Arch Ital Urol Androl. 1999 Dec;71(5):293-302.
"As regard as pure antiandrogens clinically important adverse events including gastrointestinal events, particularly diarrhea and occasional disturbances of liver function related to flutamide treatment and antabuse effect, problems with light-dark adaptation and rare interstitial pneumonitis related to nilutamide indicates the bicalutamide, due to its better tolerability profile, together with its once-daily oral administration regimen, could be considered the antiandrogen of first choice"
Fertil Steril. 2012 Oct;98(4):1047-52.
"Hepatotoxicity is a rare but possible event using low- and ultralow-dose regimens of flutamide."
Urology. 1996 Jan;47(1A Suppl):70-9; discussion 80-4.
"Bicalutamide is a new antiandrogen that offers the convenience of once-daily administration, (...) and an excellent safety profile. Because it is effective and offers better tolerability than flutamide, bicalutamide represents a valid first choice for antiandrogen therapy"
