Abstract

Intermittent androgen deprivation (IAD) is one approach to hormonal therapy for prostate cancer that has been developed with the aim of minimizing the negative effects of therapy while maximizing the clinical benefits and the patient's quality of life (QoL). It can be used in any clinical situation where continuous AD (CAD) treatment could be applied. IAD is a cyclic therapy consisting of on-treatment periods followed by observation periods, known as off-treatment periods or intervals (OTIs), and the response to therapy, or occurrence of disease progression, is monitored by measuring the patient's prostate-specific antigen (PSA) levels. The on-treatment period is generally fixed, normally lasting for 6-9 months or in some protocols until a PSA nadir of <4 ng/mL is reached. By contrast, the OTI is variable and treatment is re-instituted depending on the patient's PSA level; however, the exact trigger point is chosen empirically. The potential advantages of IAD over CAD therapy are an improved QoL, a prolonged period of androgen dependence, a reduced incidence of the side-effects normally associated with AD therapy, and a decrease in the cost of care. Results from phase II clinical studies of IAD have shown that it has good acceptance and feasibility. QoL improves during the OTIs, there is reduced toxicity, and a positive affect on bone density compared with CAD therapy. In these studies IAD appeared to have no negative effects on time to progression or survival. Further investigations of IAD are ongoing in randomized, controlled, phase III trials in the USA, Canada and Europe. Most of these studies are not yet mature and final results are awaited; however, interim analyses from some studies suggest IAD and CAD therapy are equally effective in terms of progression-free survival.