Prostate cancer benefit from exercise questionable

Prostate cancer benefit from exercise questionable

17/12/2013

Structured exercise programs benefit prostate cancer patients treated with androgen deprivation therapy (ADT) in many ways (but have no measurable effects on cardiometabolic risk factors or bone density), a literature review showed.

Strength, cardiorespiratory fitness, function, lean body mass, and fatigue all improved significantly in patients randomized to exercise interventions as compared with patients assigned to control groups.

Exercise had an inconsistent effect on adiposity, but the analysis lacked data needed to assess exercise effects on bone health, cardiometabolic risk factors, and quality of life, Steve F. Fraser, PhD, of Deakin University in Melbourne, Australia, and co-authors reported in an article published online in the Journal of Clinical Oncology.

"The most consistent finding was that exercise training improves physical performance," the authors concluded. "Resistance training consistently provided substantial increases in muscular strength and endurance, with smaller improvements also reported after aerobic training."

"The evidence also suggests that exercise training may be effective at mitigating ADT-induced fatigue," they added. "Whereas control groups generally reported increases in fatigue over time, both aerobic and resistance training seemed to help participants maintain or even reduce fatigue levels."

The results provide a basis for additional randomized clinical trials to elucidate mechanisms associated with beneficial effects and optimum exercise intensity, frequency, and duration, according to Fraser and colleagues.

Though widely used to slow tumor progression and for symptom palliation, ADT causes adverse effects that can seriously affect health and quality of life. The adverse effects include loss of bone mineral density (BMD) and an associated increased risk of osteoporosis and fractures, loss of muscle mass and increased adiposity, and reduced strength and functional capacity.

Some evidence has linked ADT to an increase in several cardiometabolic risk factors, which may predispose patients to an increased risk of cardiovascular disease, the authors noted in their introduction. Whether the adverse cardiometabolic effects translate into an increased incidence of cardiovascular events remains unclear.

Exercise training has been proposed as a means to ameliorate the cardiometabolic risk associated with ADT. Studies of older adults have shown that exercise training can increase lean body mass, decrease adiposity, reduce blood pressure, improve insulin sensitivity, enhance glycemic control, improve blood lipid levels, and favorably affect psychological well-being and quality of life.

Appropriately designed exercise interventions can maintain or increase BMD and reduce the risk of falls and fractures.

Several studies have examined the effects of exercise training in patients with prostate cancer, but none has specifically evaluated patients treated with ADT. To address the issue, Fraser and colleagues performed a systematic review of the literature and meta-analysis of relevant data.

The literature search encompassed 1980 to mid-2013. The authors selected only studies that involved prostate cancer patients treated with ADT and that included an active intervention (not just advice or patient education). They excluded studies that combined exercise training with other drug therapy or other lifestyle modifications (such as dietary intervention).

The systematic review included 14 published articles involving 10 exercise intervention studies. The studies consisted of five randomized, controlled trials and five uncontrolled trials, all of which assessed outcomes before and after the intervention.

The trials and interventions exhibited a level of heterogeneity that precluded meta-analysis.

The trial participants' mean age ranged from 63 to 72. Sample size ranged from five to 66 in the uncontrolled trials and from 50 to 155 in the randomized studies. Most patients had nonmetastatic disease.

Characteristics of the exercise interventions varied substantially among the studies. In most studies, the intervention required participation in three sessions a week for 12 weeks. Some studies involved supervised exercise sessions, and others did not. The 10 trials evaluated aerobic exercise, resistance training, or both.

In studies involving aerobic exercise, exercise intensity ranged from 55% to 85% of maximum heart rate. Interventions that involved resistance training employed different intensities and number of repetitions.

Investigators summarized the findings by outcomes evaluated:

• Bone health -- Assessed in one study, which showed no effect of exercise
• Body composition -- Assessed in all studies, which showed improvements in lean body mass and volume of specific muscle groups but no consistent effects on adiposity, body mass index, weight, or waist circumference
• Physical performance -- Assessed in all studies, which consistently yielded favorable results
• Muscular performance -- A consistent beneficial effect observed in randomized controlled trials and most of the uncontrolled trials.
• Cardiometabolic risk factors -- Evaluated in three trials, which showed no clear benefits
• Fatigue -- Evaluated in eight of 10 trials, which exhibited some heterogeneity but trended toward beneficial effects
• Quality of life -- Evaluated in all but one study and suggested benefits that varied by type of intervention across different quality-of-life domains and subscales
• PSA and testosterone -- Evaluated in six studies, none of which showed a significant effect on either measurement

The author of an accompanying editorial pointed to inconsistencies throughout the review but concluded that "the evidence in favor of exercise is arguably strong enough to consider its routine implementation to diminish musculoskeletal adverse effects in patients with prostate cancer receiving ADT -- particularly given the potential for exercise to also improve cardiovascular and overall health."

Providing exercise interventions that consistently deliver benefits to patients treated with ADT requires development of an infrastructure comprising several key components, said J. Kellogg Parsons, MD, of the University of California San Diego.

Three essentials are a cost-efficient delivery system that provides equitable access for all patients; use of standardized, reproducible methods to increase exercise; and carefully designed safety and quality-control protocols.

Even after meeting such prerequisites, implementation of an effective exercise program will require selling skeptical clinicians on the benefits of such a program.

"Overcoming this bias will no doubt require educating, and perhaps even incentivizing stakeholders as to the clinical value of exercise and advocating for its structured assimilation into the routine care of patients with prostate cancer," Parsons concluded.

 

Source: MedPage Today: http://www.medpagetoday.com/HematologyOncology/ProstateCancer/43481