Does lifestyle intervention affect prostate cancer outcomes?
Posted Dec 20 2010 12:00am
A new draft technology assessment report from the Agency for Healthcare Research and Quality (AHRQ) has addressed the impact of lifetyle interventions on prostate cancer (along with three other disorders). The draft report has been prepared as the basis for discussion at a Medicare Evidence Development and Coverage Advisory Committee (MedCAC) meeting to be held early in 2011.
From a prostate cancer point of view, this draft technology assessment says that there is no good evidence, at this time, that lifestyle modification can reliably prevent recurrence of prostate cancer or significantly delay progression of disease. Since such evidence would need to be based on large, long-term, randomized, controlled clinical trials, it has to be said that this is a fair conclusion. There have never been any large, long-term, randomized trials of lifestyle modification on prostate cancer recurrence or disease progression. At best there have been some small trials that lasted a matter of months rather than years. To quote the precise conclusion of the draft report, it states that:
The body of evidence looking at lifestyle interventions to prevent cancer recurrence is limited. We found only one RCT that attempted to address this question; however, the clinical significance of their findings is unclear.
The trial referred to is a trial by Ornish et al., which “reports a modest statistically significant decrease in PSA in the lifestyle intervention group; however, this result should be interpreted with caution as there were methodological limitations and the trial was assessed at high risk of bias. Furthermore, the clinical significance of this outcome is unclear.”
We should be clear in stating that this lack of category 1 evidence for impact of lifestyle interventions on prevention of recurrence or progression of prostate cancer does not mean that lifestyle interventions are necessarily a bad idea. All it means is that we don’t have the necessary level of evidence to recommend, implement, and cover costs associated with lifestyle intervention specifically to prevent prostate cancer recurrence or progression. Lifestyle interventions may still have impact on overall survival and on quality of life because they may result in things like significant weight loss or reduction in cholesterol levels or other factors that may reduce risk for cardiovascular disease or metabolic syndrome or other conditions associated with an increased mortality rate. Two of these other conditions are also addressed in this report. In these conditions, the draft report concludes that:
Comprehensive lifestyle interventions that include exercise, dietary changes, and at least one other component are effective in decreasing the incidence of type 2 diabetes mellitus in high risk patients and the benefit extends beyond the active intervention phase.
Comprehensive lifestyle interventions appear to have a positive impact on behavioral outcomes including exercise and dietary intake, as well as a number of metabolic variables, at least in the short-term, in all populations addressed in this report.
What’s the bottom line? Effectively, prostate cancer patients may be able to benefit from comprehensive lifestyle interventions, but as yet we have no proof that this is because of a direct effect on their prostate cancer. Rather, it may be because of effects on concommitant risks for type II diabetes or metabolic syndrome.