Androgen deprivation therapy in prostate cancer: are rising concerns leading to falling use?

To describe patterns of initiation of androgen deprivation therapy (ADT) in a population-based cohort of patients with prostate cancer.

All patients with prostate cancer in Ontario, Canada, who started ≥90 days of ADT at age ≥66 years in 1995-2005 were classified by ADT regimen: medical castration [oestrogen and/or luteinizing hormone-releasing hormone (LHRH) agonist); orchidectomy; antiandrogen monotherapy; combined androgen blockade (CAB) medical (medical castration plus antiandrogen); CAB surgical (orchidectomy plus antiandrogen). Indications for ADT were as follows: neoadjuvant (short-term before prostatectomy or radiation therapy); adjuvant (long-term with prostatectomy or radiation therapy); metastatic disease; biochemical recurrence; primary (localized disease); other. We examined trends in ADT regimen and indication over time.

The number of patients initiating ADT increased from 1995 to 2001 (2106-2916 per year) and declined thereafter to 2200-2300 annually (total n= 26,809). However, prostate cancer prevalence doubled over these years, and the rate of ADT initiation decreased from 16 to 7 per 100 person-years. Patterns varied by regimen and indication. Medical castration increased from 12% of all ADT in 1995 to 47% in 2005; orchidectomy decreased from 17 to 4%. Use for metastatic disease remained stable, but adjuvant therapy increased from <3% of all ADT in 1995 to 13% in 2005. Primary therapy was the most common indication, but decreased over time.

ADT initiation has fallen and marked changes occurred in treatment patterns for prostate cancer. Changes might be driven by increasing awareness of potential harms and costs, and by new evidence supporting ADT for specific indications.