Susan G. Lakoski, MD
Men with a high level of cardiovascular fitness at middle age had a reduced risk of developing and dying from lung and colorectal cancer later in life, according to the results of a study presented at a press conference prior to the 2013 American Society of Clinical Oncology (ASCO) Annual Meeting.
The prospective Cooper Center Longitudinal Study, which took place over a 20-year period and included 17,049 men, also found that high levels of fitness reduced the risk of dying from, though not developing, prostate cancer. Lung, colorectal, and prostate cancer are the most common types of cancer among men in the US.
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
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.
“This is the first study to explore fitness as a marker of future cancer risk prognosis,” said Susan G. Lakoski, MD, assistant professor of Medicine, University of Vermont, and the study’s lead author, in a statement. “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.
“We really need to think about measuring fitness formally to detect cancer risk, but we also need more information,” Lakoski said at the ASCO press conference. 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, in a statement.
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).
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