CHICAGO—Cardiovascular fitness in middle-aged and older men is a strong independent predictor of incident lung and colorectal cancer and remained a robust predictor of cause-specific mortality in those diagnosed with lung, prostate, or colorectal cancer, according to 20-year follow-up results of a study reported at the 2013 American Society of Clinical Oncology (ASCO) Annual Meeting.
“While poor fitness is already known to predict future cardiovascular disease, this is the first study to explore fitness as a marker of future cancer risk prognosis,” said Susan G. Lakoski, MD, MS, who is an assistant professor of medicine at the Vermont Cancer Center, University of Vermont, Burlington. “These findings provide support for the utility of fitness testing in the preventive health care settings to determine cancer risk and prognosis after cancer.”
Noting “few studies have examined the prognostic importance of cardiorespiratory fitness to predict cancer incidence or cause-specific mortality” following a diagnosis of cancer in men, the investigators examined relationships between baseline cardiorespiratory fitness and subsequent diagnosis and cause-specific mortality in the Cooper Center Longitudinal Study, a prospective observational cohort of 17,049 men undergoing a preventive health examination. Mean age was 50± 9 years.
The fitness test entailed walking on a treadmill under a regimen of changing speed and elevation. The men’s performance was recorded in established units of fitness, metabolic equivalents (METs).
Analysis of Medicare claims identified study participants who had developed lung, colorectal, or prostate cancer, the three most common cancer types among men in the United States. Mean times from assessment of cardiorespiratory fitness to cancer incidence was 20.2 ± 8.2 years and death from cancer, 24.4 ± 8.5 years. During this time, 2,332 men were diagnosed with prostate cancer, 276 with colorectal cancer, and 277 with lung cancer. All-cause mortality was 769 deaths; 347 deaths were due to cancer and 159 to cardiovascular disease.
Compared with men in lowest cardiorespiratory fitness quintile, the adjusted hazard ratio (HR) for incident lung, colorectal, and prostate cancer among men in the highest cardiorespiratory fitness quintile was 0.32 (95% CI: 0.20-0.51; P<0.001), 0.62 (95% CI: 0.40-0.97; P=0.05), and 1.13 (95% CI: 0.97-1.33; P=0.14), respectively.
“In men developing cancer, both cancer-specific mortality and cardiovascular-specific mortality declined across increasing cardiorespiratory fitness quintiles,” they noted (all P<0.001). A 1-MET increase in cardiorespiratory fitness was associated with a 14% reduction in cancer-specific mortality (HR, 0.86; 95% CI: 0.81-0.91; P<0.001), and a 23% reduction in cardiovascular-specific mortality (HR, 0.77; 95% CI: 0.69-0.85; P<0.001).
Men who had low fitness had an increased risk of cancer and cardiovascular disease even if they were not obese, suggesting patients should focus on improving their fitness, regardless of body weight. In this study, men who fell in the lowest quintile for fitness achieved less than 13.5 minutes during the treadmill exercise test if they were 40 to 49 years old, less than 11 minutes if they were 50 to 59 years, and less than 7.5 minutes if they were 60 years or older.
Dr. Lakoski concluded, “these findings provide support for the utility of fitness testing in the preventive health care settings to determine cancer risk and prognosis after cancer.”
ASCO President Sandra M. Swain, MD, FACP, said, “This important study establishes cardiorespiratory fitness as an independent and strong predictor of cancer risk and prognosis in men. While more research is needed to determine if similar trends are valid in relation to other cancers and among women, these results indicate that people can reduce their risk of cancer with relatively small lifestyle changes.”
This research was supported by the National Cancer Institute.