Worldwide, prostate cancer is the second most common cancer in men. In 2008, 899,120 cases of prostate cancer were recorded, which represents 13.6 per cent of all new cancer cases in men. In the same year, 258,133 deaths were attributable to prostate cancer. It is predicted that the number of cases will almost double (1.7 million) by 2030 [1
Prostate cancer is the most commonly diagnosed cancer in Australia and has the third highest mortality rate after lung and bowel cancers [2
]. In 2007, 19,403 new cases of prostate cancer were diagnosed and there were 2,938 deaths. The rate of prostate cancer increases rapidly from the age of 45 years [2
]. Improvements in five-year survival rates have been observed for prostate cancer, from 57% to 85% [3
With improved survival rates, cancer survivors can derive substantial functional, physical, and psychological benefits from physical activity [4
]. In men with prostate cancer, systematic review evidence suggests that physical activity has the potential to enhance health-related quality of life, muscular fitness, and physical functioning, as well as reduce fatigue [5
]. Although these findings are promising, additional studies (especially randomised controlled trials in cancer types other than breast cancer) need to be conducted to substantiate the work in this area [4
For prostate cancer survivors who have been treated with androgen deprivation therapy (ADT), there may be additional reasons to undertake physical activity. Previous research has shown that after 36 weeks of ADT prostate cancer patients decreased whole body lean mass by 2.4%, bone mineral content and density of 2.4%, serum testosterone of 93.3%, PSA levels of 98.2%, and haemoglobin levels of 8.8%, as well as increases in fat mass of 13.8% [6
]. Assisting men who are receiving ADT to become physically active is, therefore, necessary to reduce the risk of obesity, osteoporosis and sarcopenia.
Many men reduce their involvement in physical activity following a diagnosis of prostate cancer [7
]. Although evidence is mounting on the benefits of regular physical activity for prostate cancer survivors, the prevalence of physical activity among this group is modest and varies widely between studies [5
]. To improve the uptake of physical activity among prostate cancer survivors, strategies need to be developed and tested for their effectiveness.
Research has highlighted gaps in information provision regarding the type and amount of physical activity that prostate cancer survivors should undertake [8
]. A key challenge is to make such information accessible to all prostate cancer survivors. One way in which this information may be conveyed is via clinicians with referrals to accredited exercise physiologists. However, research has shown that most prostate cancer survivors do not recall receiving information from clinicians about integrating physical activity into their lives [8
]. Patients have reported clinicians are the most important conveyors of information [9
] and a prescription or referral to an exercise physiologist may be effective in promoting physical activity among patients.
Evidence on the efficacy of prescriptions of physical activity in general practice (GP) has been mixed [10
]. In general, GP prescriptions of physical activity have led to a moderate increase in physical activity and fitness levels for 6 to 12 months [14
]. There have been few studies, however, on the efficacy of physical activity prescriptions among people with specific chronic health conditions and where physical activity prescriptions are supplemented with other interventions, such as brief counselling [11
]. Findings from this limited research have yielded less than optimal results. Overall however, the findings of previous studies are sufficiently strong to warrant further work in this area. The experience of cancer may mean that survivors more readily comply with the advice of their clinicians, which would result in higher levels of physical activity from an intervention that utilises clinician referral to an exercise physiologist in this population.
Accredited exercise physiologists are specialists who can provide prostate cancer survivors with expert advice on how to increase their physical activity levels safely. Since 2006 exercise physiologists accredited by Exercise and Sport Science Australia (ESSA) have been part of Australia's universal healthcare system (Medicare). Medicare provides access to free or subsidised treatment from medical practitioners, such as accredited exercise physiologists. Given their place in the health system, accredited exercise physiologists are well positioned to make an important contribution to increasing the health of prostate cancer survivors.
A criticism of previous randomised controlled trials that have examined physical activity in cancer survivor populations is that they do not incorporate a theoretical framework. Theoretical frameworks are necessary to guide the development and evaluation of interventions so that the mechanisms that change behaviour can be understood and replicated in future interventions [15
]. There are compelling reasons for using social cognitive theory [16
] to underpin a physical activity intervention for prostate cancer survivors. First, recent research conducted with (a) participants of similar ages to prostate cancer survivors who are likely to participate in this planned study [17
], and (b) cancer patients [18
] have shown that social cognitive theory constructs explain substantial amounts of variance in physical activity. For example, in a study of middle-aged and young-old adults, social cognitive theory constructs explained 71% of the variance in physical activity [17
]. Second, social cognitive theory constructs are not only predictive of health behaviours, but provide avenues for modifying them [16
The main determinants of health behaviour in social cognitive theory are self-efficacy, outcome expectations, goals, and socio-structural factors [19
]. Self-efficacy is central to this conceptual model, and "refers to beliefs in one's capabilities to organise and execute the courses of action required to produce given attainments" (p. 3, [19
]). Distinctions can be drawn between various types of self-efficacy, with task and self-regulatory (coping) self-efficacy common in the exercise and physical activity literature [21
]. Task self-efficacy refers to the belief in one's ability to perform a given motor skill successfully (e.g., walking briskly for 30 minutes), whereas self-regulatory self-efficacy refers to one's ability to perform the skill under conditions that may be challenging to successful performance (e.g., inclement weather, tiredness).
Outcome expectations refer to the expected effects of one's behaviour [19
]. These effects may be physical (beneficial or detrimental), social (favourable or adverse), or self-evaluative (positive or negative). Goals provide guidance to, and incentives for, behaviour. In social cognitive theory, goals are classified as being either proximal or distal [19
]. Proximal goals are essentially equivalent to intentions and guide current behaviours, whereas distal goals orientate future behaviours. Socio-structural factors are facilitators and impediments to healthy behaviours. These factors may be personal or situational, or lie within the health system. Enhancing physical activity-related self-efficacy in prostate cancer survivors and assisting them to develop positive outcome expectations, set beneficial goals, and reduce perceived impediments may result in higher physical activity levels.
Our pilot work indicated that outcome expectations for prostate cancer survivors to perform physical activity reflected psychological and physical benefits that can be attained through participation, as well as from the context of activity, i.e. socio-structural factors, including attractive locations, opportunities for spending time alone, social interaction [8
]. Conversely, impediments to participation included limited confidence following treatment, lack of time, co-morbidities, and age-related functional decline. Despite the benefits of physical activity, men in this study did not recall receiving advice from their clinicians about physical activity and few reported being referred to exercise professionals. Given these findings, interventions to increase physical activity in prostate cancer survivors that incorporate referrals from clinicians to exercise professionals and a well constructed theoretically tailored physical activity program may achieve positive outcomes.
Study aims and hypotheses
The primary aim of the ENGAGE study is to compare the efficacy of a clinician referral and 12-week, supervised, exercise physiologist-led physical activity program compared to usual care (no referral to the physical activity program and typically minimal advice about physical activity) in improving the physical activity levels of prostate cancer survivors at three post-intervention time points:12 weeks, 6 months, 12 months. We hypothesise that participants in the intervention condition will be more physically active than participants in the control condition.
A secondary aim is to determine the effects of the clinician referral and physical activity program on the psychological well-being, quality of life and objective physical functioning of prostate cancer survivors. At the three post-intervention time points (12 weeks, 6 months, 12 months), we hypothesise that the clinician referral and physical activity program will improve participants' quality of life and decrease anxiety and depressive symptoms over and above changes on such measures that participants in the control condition may experience at post intervention. We will measure objective physical functioning at baseline and 12 weeks only, and hypothesise that participants in the intervention condition will improve their exercise capacity more than those in the control condition.
A further aim is to assess the impact of the intervention on main health determinants using the social cognitive theory and whether these determinants mediate behaviour change. We hypothesise that the intervention will have positive effects on self-efficacy, outcome expectations, goals, and socio-structural factors; and that self-efficacy will have a direct association with physical activity and an indirect association, mediated by outcome expectations, goals, and socio-structural factors.