Exercise and Cancer Prevention


Feb. 25, 2010 – For years, the medical community has been telling the public that exercise is good for your health. Most people now know it reduces the risk of such conditions as heart dieases and diabetes. But according to public health experts, exercise also plays a role in preventing cancer. On this edition of Breakthroughs in Cancer Research, Kathleen Wolin, ScD, explains why researchers think physical activity has such a powerful effect on cancer and cancer survival. Wolin, an epidemiologist at the Siteman Cancer Center and assistant professor of surgery at Washington University in St. Louis, also discusses studies examining the influence of exercise on colon cancer risk, side effects from hormone therapy for prostate cancer and incontinence after prostatectomy. 

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On this edition of Breakthroughs in Cancer Research, we'll talk about research that looks at how physical activity and weight affect a person's risk for cancer and cancer survival.

Host: Thanks for downloading this podcast from the Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine in St. Louis. I'm Gwen Ericson, and I'm talking with Dr. Kathleen Wolin, an expert in cancer prevention and control at the Siteman Cancer Center. Dr. Wolin, thank you for joining us.

Wolin: Thanks for having me.

Host: It's interesting that something as basic as losing weight or exercising could influence a disease as serious as cancer. Before we get into specifics about some of your studies, let's talk a little bit about the thinking on why exercise and weight have such profound effects.

Wolin: Well Gwen, I think we're still learning why these factors work, but the data is pretty clear that they do have a really important influence. We know that physical activity and weight act independently of each other, so even among folks who are lean, physical activity can have an effect. And even among folks who are physically active, weight can matter. And why that is we are still exploring. It in some ways depends on the specific cancer.

So for breast cancer, people have long thought that obesity and physical activity are acting through the hormone cascade of female hormones. But there's emerging evidence that physical activity may also act on breast cancer by influencing insulin and insulin-related pathways in our biology. Similarly, with something like colon cancer, physical activity has a really profound effect. We think that it may be related to the insulin pathway similar to breast cancer. But long-term physical activity, consistent physical activity, can lower your body's systemic inflammation. And so there's some thought that physical activity may be acting by lowering inflammatory levels within the body and having a prevention effect that way.

Host: You mention physical activity and colon cancer. Can you tell me more about that?

Wolin: We've done a couple studies that look at risk of colon cancer and physical activity, and I think the thing that really we take away from that is how consistent the data is. There have been over 50 studies that have looked at the association between a physically active lifestyle and risk of colon cancer. And we just see a consistent risk reduction across the board. We think it's about a 25 percent risk reduction. So that would mean people who are most active have about a 25 percent lower risk of colon cancer than people who are the least active. And I think the other thing that's really compelling about that data that came out of our study from the Nurses’ Health Study cohort is that you don't have to be running marathons. We're not talking about needing to get out there and run 10 miles a day. This kind of benefit can be seen with just walking 30 minutes a day. So it doesn't require a gym membership. It doesn't require expensive equipment. It just requires having a good pair of sturdy shoes and getting out there and doing it. Whether it's outside or inside, whatever works best for you is the way that you can go about doing it.

Host: Does that research suggest that virtually anyone can reduce colon cancer risk with exercise?

Wolin: Those populations were pretty much average risk. And so one of the questions we haven't really answered yet is whether or not individuals who are at a higher risk can see the same kind of benefit from physical activity. Right now we're doing a study of folks who are at increased risk for colon cancer because they've had a polyp found on colon cancer screening. And we want to see if by involving them in physical activity, we can reduce their risk of polyp recurrence and as a result possibly their risk of developing colon cancer.

Host: Another study you're conducting involves men with prostate cancer. Can you tell me more about that?

Wolin: These are men who have undergone treatment for their prostate cancer and as part of that treatment were on androgen-deprivation therapy, or hormone therapy. And while that hormone therapy has been shown to have beneficial effects in terms of reducing their risk of prostate cancer recurrence, it has some pretty noteworthy side effects. In general, you don't feel good. It's been somewhat compared to going through menopause. It has effects on your bone – you lose bone density – so it can increase your risk of osteoporosis. It causes a loss of lean muscle mass. A lot of people report that it interferes with their sleep. So they're just not sleeping as well. Just sort of a general decline in quality of life. It can result in some weight gain.

So these were all issues that we were concerned with, and we wanted to see if we could offset some of those side effects by using physical activity. We wanted to see if we could improve their body composition. So increasing their muscle mass, increasing their bone density, through exercise. And our question was particularly whether there was a difference in what we saw from having men lift weights and do weight training – a resistance training program – versus men doing an aerobic training program. So as we were talking about before, simply getting out and walking a good amount each day. And so that study has concluded. We are in the process of analyzing the data, and we don't have the results yet. But the thing for us that's really an important question is whether or not we can offset some of the side effects of drugs with something other than drugs. And can we have people undertake behavior changes and lifestyle changes that will improve their health outcomes without having to take another drug, which may have certain side effects.

Host: And one of your studies explored the effect of exercise on incontinence after prostate cancer surgery.

Wolin: Yes. So we did a study based on some data that had been collected here with Dr. Adam Kibel in urology. What we saw was that we know that incontinence is a really big issue for men after they have prostatectomies. It's a major concern and generally limits their quality of life. And what we saw is that men who are leaner tend to experience less incontinence, and men who are physically active tend to experience less incontinence. In particular, physical activity can help offset some of the negative consequences of being obese in terms of your incontinence. And so we are looking to follow that up with some additional studies and hopefully get to the point where we can start thinking about some weight loss and exercise interventions to offer our patients in that regard.

Host: Are there guidelines for cancer survivors as far as how much or what kind of exercise they should do?

Wolin: Siteman hosted this summer a meeting of experts from around the globe to pull together some exercise guidelines for cancer survivors. So one of the things that's become apparent in clinical care is that physicians and survivors aren't really clear on what is safe for them to do and what the possible benefits and risks are of participating in an exercise program. So if you think back to cardiac rehab a couple decades ago, the thought was that after you have a heart attack you should rest. And you needed to rest in order to recover. And then data started coming out suggesting that actually getting up and moving and being active was more beneficial.

And we are seeing a very similar sort of thing happen in the cancer care community. A lot of the treatments for cancer are debilitating and result in some really serious fatigue and quality of life side effects. The thought was that folks needed to rest in order to counter those effects. What's really starting to emerge is this rapidly increasing body of science that physical activity – and again we're not talking about marathon running here; we're talking about moderate intensity activities like walking or getting on an exercise bike. For people who might have an infection risk and can't get out and walk, that moderate-intensity activity has a whole host of beneficial effects. It can reduce fatigue, which is a major concern for folks undergoing treatment and after treatment. It can improve quality of life.

And so really I think the message that we were able to come to is that under most circumstances, exercise is something that is safe for cancer survivors to undertake. We looked at both adult and pediatric cancer patients. We have a paper in press that reviews the data on exercise interventions for hematologic cancer patients, both adults and children. And again we see even with the limited amount of data that's there that we're not seeing adverse events happening. It's safe for individuals to undertake these supervised moderate-intensity exercise programs in hematologic cancer patients. And for the cancer population more broadly, particularly breast cancer patients where a lot of the research has been undertaken, that exercise is not only safe but has some real benefits.

Host: For some people, it’s difficult to get out and exercise. And some research has been looking into that, right?

Wolin: We know that certain folks just don't have the same kind of access that others do. And it's an area where there’s some really exciting work coming from some of my colleagues here at Washington University. We know that if you live in a neighborhood that has a lot of crime or that you don't feel safe getting out and walking in after work, that's going to limit your ability to be physically active. And so understanding and trying to work with folks so we can find places for them to be active. We can understand what limits their ability to be physically active. Those are all part of what we're trying to do when we're working with cancer survivors or working in a cancer-prevention setting. We really have to be attuned to the different challenges that individuals face based on where they live or their socioeconomic background when we start talking about encouraging folks to be physically active. We have to make sure that we are understanding the context that people are living and working in when we talk about these lifestyle changes.

Host: What can we look forward to in the future on this topic?

Wolin: We have a lot of really exciting research that's going on here at the Siteman Cancer Center across all of these issues. And so we're really going to start seeing a much bigger impact of these things. It 's really exciting to be able to tell people there are things they can do to reduce their risk of cancer and to improve their outcomes after a cancer diagnosis. And we're going to continue to do research in that area and be able to refine that message and give people the best information that we can.

Host: Dr. Wolin, thank you so much for talking with me today.

Wolin: It's my pleasure to be here.

Host: You can find out more about the Siteman Cancer Center's cancer prevention research online. Go to www.siteman.wustl.edu and click on the “Research Programs” link at the top of the page. Follow the links to “Prevention and Control” to explore ongoing research in this area. You can also find out more about Dr. Wolin and her research on the Web site of the Washington University Department of Surgery at www.surgery.wustl.edu. Look for the research faculty directory and you will find Dr. Wolin listed there.