Long-term follow-up of 60 incarcerated male sexual offenders pharmacologically castrated with a combination of GnRH agonist and cyproterone acetate

Herstedvester Prison is a penal institution and center for treating violent sexual offenders in Denmark. From 1989 to 2014, 60 dangerous sexual offenders were treated with the combination of a GnRH agonist and cyproterone acetate, providing pharmacological castration and androgen receptor blockade. Five years after initiation of treatment, 81.7% (95% CI 74.4, 92.1) of offenders were released. Twenty years after treatment initiation, 30.6% (95% CI = 19.6, 47.6) of offenders had a relapse to any crime, including sexual offense, and 13.6% (95% CI = 11.5, 33.3) had a relapse to sexual crime. Treatment was paused or discontinued for 44.1% (95% CI = 31.7, 61.4) of offenders. Cessation was not associated with higher recidivism to any crime (hazard ration [HR] = 2.2; 95% CI = 0.8, 6.3; p = 0.14), but the risk of a new sexual offense was 7.7 (95% CI = 1.4, 42.8; p = 0.02) times higher among those who stopped treatment, compared to those who continued it.