Recommended exercise leads to 'fairly profound' mortality reduction for cancer survivors
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For individuals diagnosed with cancer, guideline-concordant exercise reduced all-cause mortality by 25% compared with patients with cancer who did not exercise, study results published in Journal of Clinical Oncology showed.
The analysis, led by exercise scientist Lee W. Jones, PhD, chief of Memorial Sloan Kettering Cancer Center’s Exercise Oncology Service, reported a difference in median survival time of about 5 years for those who exercised vs. non-exercisers after a cancer diagnosis.
“When we talk to individuals who have been diagnosed with cancer and cancer survivors, one of the most common questions is, ‘What can I do that can potentially impact not only how I respond to treatment, but also minimize the chances of this disease coming back?’” Jones told Healio. “People know that cancer typically will have a negative impact on how long they might live, and they are very interested in what they can do — beyond traditional cancer approaches — to live as long as they can with the best quality of life.”
Jones spoke with Healio about the motivations for this study, its findings, and his hopes for its long-term impact on cancer care and survivorship.
Healio: What inspired you to conduct this study?
Jones: There haven’t been many studies on this topic, and the studies that have been done are quite small and focused on one cancer type at a time. So, there hasn’t been a comprehensive assessment of this question across all different types of cancers. We had an opportunity to work with a robust dataset in the context of the Prostate, Lung, Colorectal and Ovarian Cancer (PLCO) screening trial that was done many years ago. This is publicly available data — the only difference is, I went in and looked at the data available on individuals diagnosed with cancer. It turned out there were over 11,000 individuals with follow-up data. We could also look at the relationship not only between exercise and overall survival, but also cause-specific survival, which is very important.
Healio: How did you identify and assess this patient population?
Jones: Part of the PLCO screening trial looked at the effect of screening on cancer mortality. This was a very large study with approximately 140,000 individuals. Of course, over a period of 20 years, many of those individuals were diagnosed with cancer. In this particular study, the participants were sent a survey about 9 years after they enrolled. It asked various questions, including those about exercise.
We knew it was likely that quite a few individuals were diagnosed with cancer who had also completed this questionnaire, so we went through the database and extracted that data. This is where the 11,000 or so individuals came from, and they represented a broad range of cancers. This was not just breast cancer or prostate cancer — it included 19 different types of cancer. This allowed us to take a pan-cancer approach to our analysis.
In the context of this study, the exercise exposure was self-reported exercise. These were individuals who were reporting how much exercise they had done in the past and how much exercise they were doing currently. We had to rely on people’s honesty and accurate recall. However, I think these questionnaires are good at determining whether a person is exercising or not. From that, we could then determine how many were meeting the current national guidelines vs. those who weren’t. Then we looked at things like overall survival and cancer-specific survival after controlling for these other potential confounders.
Healio: What did you find?
Jones: In terms of overall survival, we found there was a significant benefit from being a regular exerciser according to the guidelines vs. not exercising (not meeting guidelines). Compared with not exercising, exercise consistent with guidelines was associated with a significant decrease in the risk for all-cause mortality, which was derived from a reduction in the risk for dying of cancer and dying of other, non-cancer-related causes.
You could say that is to be expected, but there’s a bit of a difference between individuals who have been diagnosed with cancer vs. the general population. It’s a different circumstance. There is often a perception that when a patient is diagnosed with cancer, the treatments can have an effect, but that there’s not much they can do beyond that. I believe these results show that if you exercise, it can have an impact on overall survival. The survival benefit was about a 5-year additional survival benefit. In other words, looking at median survival in those who didn’t exercise, the survival was about 14 years, whereas for those who did exercise it was 19 years. That’s profound — if a drug demonstrated that kind of impact, it would be major news.
The caveat, of course, is that this was not a randomized trial. We weren’t assigning individuals to exercise vs. not. It’s an association; it’s not causality. However, it’s a strong signal and gives us confidence now to move forward with randomized trials to see if we can replicate that benefit.
It was also very encouraging to see that the overall benefit was significant in most of the cancers we studied, which is encouraging for individuals diagnosed not only with breast cancer, but maybe liver cancer or colorectal cancer. There was a profound overall survival benefit that was consistent across cancers.
Healio: Why was the decrease in all-cause mortality especially encouraging?
Jones: Something we tend to forget about individuals diagnosed with cancer is that they’re at increased risk for recurrence, but they are also at increased risk for dying of something else, such as cardiovascular disease. We’ve studied this issue for a long time. We know that although cancer treatments are effective at slowing tumor growth, they also have detrimental effects on other organs in the body, such as the heart and lungs. Additionally, cancer survivors have a 30% increased risk for developing cardiovascular disease.
If you think about all the drugs we test, what are we concerned about? We are interested in the efficacy of the drugs, of course, but we are also concerned about the potential toxicity. It’s always that balance of efficacy vs. toxicity. Many cancer drugs have a cancer-specific benefit, but then toxicities overtake or attenuate that progress. The result is that the overall survival benefit can often end up being lower than anticipated.
So, with something like exercise, we get a double whammy. What’s novel is that these patients not only appear to get a cancer-specific benefit, but they also receive cardiovascular benefits as well. When you put those things together, you get a fairly profound overall survival benefit.
Healio: How do you hope these findings will impact the way exercise is recommended for patients with cancer?
Jones: There is a viewpoint that because guidelines are in place recommending exercise for these patients that we’ve done everything we need to do. I don’t believe that is the case at all. Just because there are guidelines in place doesn’t mean that oncologists or other oncology providers are now recommending exercise to their patients. One reason they might not is because of the level of evidence. I hope that although these guidelines are in place, this study and others like it can further confirm their value.
The current guidelines haven’t been driven by a survival benefit — they’re driven by exercise as a beneficial effect on things like quality of life and fatigue. In oncology, what moves the needle is being able to improve these hard clinical endpoints. This isn’t to say that quality of life and fatigue aren’t important, but when it comes to clinical recommendations, we typically make them based on hard clinical benefit. Although these data are observational, I would hope that this association with overall survival benefit would encourage more clinicians to recommend exercise to individuals with cancer. The findings reinforce that the guidelines are important and have merit. I hope these results encourage more oncologists and oncology professionals to apply those guidelines.
Healio: Is there anything else you’d like to mention?
Jones: We must keep in mind that this is association data, not causality. It’s always important to emphasize that although these data show that there might be a signal, we now need to prove this in randomized, controlled trials. That’s something we hope to discuss a few years from now.
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For more information :
Lee W. Jones, PhD, can be reached at Memorial Sloan Kettering Cancer Center, 1275 York Ave., New York, NY 10065; email: jonesl3@mskcc.org.
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