This finding makes it clear that patients should be advised that they need to achieve a certain fitness level, and not just be told that they need to exercise. Unlike patient-reported exercise behavior, Lakoski said, fitness can be objectively and accurately measured in a clinical setting.
Telling patients to exercise is not enough. Physicians can now be clear that the likelihood of developing or even dying from cancer will rise if patients fail to maintain good cardiovascular health, according to the lead author of a study released today that explores the links between fitness and cancer.
The prospective Cooper Center Longitudinal Study, formally unveiled in Chicago at the Annual Meeting of the American Society of Clinical Oncologists (ASCO), found that men with a high level of cardiovascular fitness at middle age reduced their risk of developing lung and colorectal cancer. While these men still developed prostate cancer at rates similar to the overall population, those in better health trimmed their chances of dying from any of the three diseases.
The study, which took place over a 20-year period and included 17,049 men, looked at lung, colorectal and prostate cancer because they are the most common cancers seen in men. “This is the first study to explore fitness as a marker of future cancer risk prognosis,” Susan G. Lakoski, MD, assistant professor of Medicine, University of Vermont, the lead author, said recently.
“This finding makes it clear that patients should be advised that they need to achieve a certain fitness level, and not just be told that they need to exercise.” Unlike patient-reported exercise behavior, Lakoski said, fitness can be objectively and accurately measured in a clinical setting.
At a mean age of 50 years, study participants had a single cardiovascular fitness assessment, consisting of walking on a treadmill at various speeds and elevations. The participants were divided into five groups depending on fitness performance, based on established units of fitness called metabolic equivalents (METs). The research team then analyzed Medicare claims over a median follow-up period of 20 to 25 years to identify participants who had developed lung, colorectal, or prostate cancer.
The analysis found that 2332 men had been diagnosed with prostate cancer, 276 with colorectal cancer, and 277 with lung cancer. Of the total number of participants, 347 had died of cancer and 159 had died of cardiovascular disease.
The risk of lung cancer was reduced by 68% (hazard ratio [HR] = 0.32; 95% CI, 0.20-0.51; P < .001) in men who had the highest level of fitness compared to those with the lowest level. The risk of colorectal cancer was reduced by 38% (HR = 0.62; 95% CI, 0.40-0.97; P = .05), but the risk of prostate cancer showed no significant change.
Among those who developed cancer, men who had a higher level of fitness at middle age had a lower risk of dying from lung, colorectal, and prostate cancer, as well as from cardiovascular disease. A small difference in fitness (1MET) resulted in a 14% reduction in the risk of dying from cancer (HR = 0.86; 95% CI, 0.81-0.91; P < .001) and a 23% reduction in the risk of dying from cardiovascular disease (HR = 0.77; 95% CI, 0.69-0.85; P < .001).
Researchers adjusted for smoking and other factors, such as body mass index and age. Men on the lower end of the fitness scale had an increased risk of cancer and cardiovascular disease, even if they were not obese.
“We really need to think about measuring fitness formally to detect cancer risk, but we also need more information,” Lakoski said. There also remains a need for data on other types of cancers, data on women, and data on change in fitness as it relates to outcome.
Although more studies are needed, “these results indicate that people can reduce their risk of cancer with relatively small lifestyle changes,” said ASCO President Sandra M. Swain, MD.
Lakoski SG, Barlow C, Gao A, et al. Cardiorespiratory fitness and risk of cancer incidence and cause-specific mortality following a cancer diagnosis in men: The Cooper Center longitudinal study. J Clin Oncol. 2013(suppl; abstr 1520)