Exercise and Prostate Cancer—the evidence stacks up for benefits
New research adds credence for why men ought to exercise both before and after a prostate cancer diagnosis to maximize their chances of longer survival and/or improved quality of life.
January 27, 2014 -- A growing body of research suggests that exercise benefits men with prostate cancer, and now a new study may have determined one of the reasons why. In findings presented by several PCF-funded researchers this week in San Diego at the American Association for Cancer Research – Prostate Cancer Foundation Conference on Advances in Prostate Cancer Research, men with a history of brisk walking prior to a diagnosis of prostate cancer had healthier-looking, more normally shaped blood vessels in their prostate tumors after diagnosis.
The researchers had previously shown that small, irregularly shaped vessels in human prostate tumors were linked to an increased risk of death in men with prostate cancer. “We hypothesized that brisk walking and vigorous activity would be associated with larger, more regularly shaped vessels in human prostate tumors,” says the researchers.
To test their theory, they reviewed the self-reported physical activity levels of 572 men in the Health Professionals Follow-up Study prior to a diagnosis of prostate cancer. All the men in the study underwent surgery to remove their prostate gland after their cancer was diagnosed. The researchers examined post-surgical tissue samples of these men and found that those who reported the fastest walking pace (3.5 to 4.5 mph) prior to their diagnosis of prostate cancer had more normally shaped blood vessels in their tumors compared to men with the slowest walking pace (1.5 to 2.5 mph).
This may be quite important, say the researchers, because more normally shaped vessels in prostate tumors may inhibit cancer spread in the body and might also improve men’s response to anti-cancer therapies.
"It’s easy for people to see the obvious benefits exercise has on the outside of the body, but harder to imagine that it may have positive internal effects on the prostate itself," says Dr. Lorelei Mucci, a PCF Young Investigator and an author on the study. “But this study documents the benefits exercise can confer to a prostate tumor, which may make that tumor less of a threat to the man’s life,” she says.
Interestingly, and somewhat surprising to the researchers, says Mucci, was that while brisk walking was associated with a positive effect on the shape of a tumor’s vasculature, more vigorous levels of exercise, such as running or cycling, did not seem to have an effect of tumor vessel shape. “Vigorous exercise, such as running or rapid cycling, is associated with a decreased risk of dying of prostate cancer,” says Mucci, “but from these findings, it seems as though the benefits to men from higher levels of exercise may be coming from a different mechanism of action.” Mucci and another PCF-funded researcher, Dr. Steven Finn, are currently studying the effects of exercise on tumor cells that have broken free from the prostate gland and entered the circulatory system.
Other studies show benefits of exercise for men with prostate cancer
Dr. Stacey Kenfield, a Prostate Cancer Foundation Young Investigator and a presenter on the Brisk Walking study, also first-authored a study published in the Journal of Clinical Oncology in 2011 that looked at physical activity and outcomes for men in the Health Professionals Follow-up Study diagnosed with prostate cancer. That study found that:
- Men who walked briskly for 90 minutes or more per week lower their risk of death from any cause by 46% compared to men who men who walked less quickly and less often.
- Men who exercised vigorously (e.g., biking, tennis, jogging, swimming) three or more hours per week had a 61% lower risk of death from prostate cancer compared to men who exercised vigorously less than one hour per week.
- Both non-vigorous and vigorous activity lowed men’s risk of death from any cause.
And a brand new study, published this month in the Journal of Physical Activity & Health, found that men diagnosed with cancer who burned 12,600 kilojoules (kJ) or more a week doing physical exercise (such as walking or stair climbing) cut their risk of death from any cause by half, compared to men whose weekly exercise burns only added up to 2,100 kilojoules a week. (12,000 kJ converts to 3,011 calories.)
Hitting that level of energy burn requires clearance from your doctor and personal commitment: a 170-pund man who walked briskly (pace 3.5 mph) for an hour and a half, seven days a week, would burn 12,887 kilojoules, or 3,080 calories a week.
Another PCF-funded researcher who was an author on the Brisk Walking study presented at this week’s AACR-PCF meeting, Dr. June Chan of the University of California, San Francisco, has reported in the past that vigorous exercise changes the expression of 184 genes; specifically, Chan reported at the 2012 American Society of Clinical Oncology annual meeting that several genes thought to thwart cancer progression were up-regulated in men who exercised vigorously three hours a week, or more.
Understanding how exactly exercise benefits men with prostate cancer is important, says Dr. Jonathan Simons, president and CEO of PCF, because once scientists know what genetic or other biological changes are in play that can extend survival, it might be possible to formulate therapies that mimic, or even enhance, the benefits of physical activity. Additionally, such knowledge may help explain why some men with prostate cancer who have always exercised robustly, progress in their disease, despite that fact.
“Knowledge is power,” agrees Dr. Howard Soule, chief science officer of PCF, “and this new [AACR-PCF] study on brisk walking and tumor vessel morphology definitely raises the bar for what we know in terms of how exercise may affect men with prostate cancer.” Soule adds that the time may be ripe now for funding a prospective study to more definitively address this issue.
New finding on Obesity and prostate cancer
Another study presented at the AACR-PCF meeting this week, with PCF-funded Dr. Adam Dicker of Thomas Jefferson University in Philadelphia as a study author, found that men who were either obese or overweight had a higher risk of local tumor invasiveness at the time of their surgery to remove a cancerous prostate. Specifically the study noted:
- Men with a body mass index (BMI) of greater than 29kg/m2 (generally men with BMI’s of 30 or more are considered obese) were more likely to have positive surgical margins at surgery, a trend towards worse seminal vesicle invasion, and extension of their cancer beyond the borders of the prostate gland.
- Men whose tumors were deemed intermediate-risk pre-operatively, and who had a BMI greater than 29kg/m2, were twice as likely to require radiation therapy in addition to surgery to treat their prostate cancer.
Because exercise is well-known to lower body weight, especially when combined with a healthy meal plan, this study adds weight (mea culpa on the pun) to the case for all men to discuss a sensible exercise plan with their doctor.
Exercise as a means to improve quality of life in men with prostate cancer
Prior research has shown that exercise can significantly lessen treatment-related fatigue for men with prostate cancer, be it early in the course of their disease or late. And now, a new study published in the Journal of Clinical Oncology (JCO) finds that for men undergoing androgen-deprivation therapy (ADT) for their prostate cancer, exercise can lessen a host of adverse side effects of their treatment.
Androgen deprivation therapy is commonly used to starve prostate tumors of the male hormones, such as testosterone, that can drive tumor growth, and has been shown to slow tumor progression and improve survival times in appropriately selected patients. Yet, this treatment can cause several unpleasant side effects that lower a man’s quality of life. In an accompanying editorial to the JCO study, Dr. J. Kellogg Parsons, of the Moores Comprehensive Cancer Center, at the University of California, San Diego, notes that ADT can cause “dramatic decreases in lean body mass, physical performance, muscle strength, and bone mineral density.” Lower bone mineral density can increase the risk of fractures, and decreased strength can increase the risk of falls, which, in turn, can cause fractures, especially in bone that has become less dense due to ADT.
Other adverse side effects to ADT, according to the JCO study authors, are: decreases in sex drive and erectile function; increased fatigue and depression and cognitive ability; increased blood fats and unhealthy cholesterol levels and other metabolic dysfunctions that can lead to diabetes or, potentially, heart disease in some men.
In order to determine if exercise may ameliorate, or lessen, such side effects, researchers at Deakin University in Australia, reviewed several studies that had looked at the effects of exercise on men undergoing ADT. While there was variance between the studies, the authors found that exercise consistently improved men’s physical performance in terms of muscular strength and endurance as well as their ability to do aerobic exercises, such as brisk walking.
The study authors noted that positive changes in muscular and aerobic fitness quite often resulted in improvements in men’s ability to function in their daily lives. And mimicking other study results, they found that exercise seemed to lessen fatigue. “Whereas control groups [not assigned to exercise] generally reported increases in fatigue over time, both aerobic and resistance [weights or bands] training seem to help participants maintain or even reduce fatigue levels,” wrote the authors. They postulated that exercise might offset the tendency of ADT to lower blood levels of oxygen-carrying molecules, hemoglobin, that when low often cause fatigue.
The findings were insufficient, say the authors, to provide exercise treatment regimens specific to men receiving ADT, but in the accompanying editorial, Kellogg said, “…based on the data in this review, 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.”
Because half of men who receive a diagnosis of prostate cancer in the U.S. are prescribed ADT within a year of their diagnosis, understanding the potential benefits of exercise in this group of men is of particular importance to managing this disease.
Overall says Dr. Simons, each man should sit down with his doctor and discuss what level of exercise program would be best for him. "Doubtless exercise is good for humans and will benefit men with prostate cancer in various ways, when a program is tailored to an individual patient," says Simons, a clinical oncologist. “As a physician, these new research findings give me added confidence in advising my patients that exercise will likely benefit them when prescribed appropriately; as a scientist, I’m excited that each day we are uncovering more and more about exactly why exercise may benefit various groups of men, and how this new information can be incorporated into future or ongoing research studies."