Initiation of androgen deprivation therapy (ADT) for prostate cancer (PCa) is declining and patterns of use are changing, according to recently published data from a Canadian study.

Using a population-based cohort of 26,809 patients in Ontario who started ADT from 1995 to 2005, researchers found that the rate of ADT initiation declined from 16 to 7 per 100 person-years even though PCa prevalence doubled during that period. The number of patients initiating ADT increased from 1995 to 2001 (2,106-2,916 patients per year) and decreased thereafter to 2,200-2,300 patients per year by 2005.

Additionally, the study revealed that patterns of ADT initiation varied by regimen and indication. Medical castration rose from 12% of all ADT in 1995 to 47% in 2005, whereas orchidectomy declined from 17% to 4%, Murray Krahn, MD, of Toronto General Research Institute, and colleagues reported in BJU International (2011;108:1588-1596).

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ADT use for metastatic disease remained stable but adjuvant treatment increased from less than 3% of all ADT in 1995 to 14% in 2005.

The trends could be related to the declining prevalence of late-stage disease, a growing appreciation of the potential adverse effects of ADT, and emerging evidence supporting selected indications and regimens, the researchers observed

The study cohort consisted of PCa patients in Ontario who started 90 days or more of ADT at age 66 years or older (mean 75.5 years).

Dr. Krahn’s group noted that ADT was originally used for metastatic disease, but it is now used for many other indications. They also observed that there has been growing concern about the costs and adverse effects associated with wider ADT use. Documented adverse effects of ADT include hot flushes, sexual dysfunction, loss of libido, decreased bone mineral density, and increased fat mass.

The investigators noted that the main strength of the study was its comprehensiveness. The study evaluated all regimens and all indications for ADT in a large population-based sample of patients with PCa over 11 years. In a discussion of limitations, they pointed out that they described only initial ADT use and indication.

Although they examined duration of ADT to determine some indications (such as neoadjuvant and adjuvant), they did not describe duration beyond 90 days or changes in regimen.