Roxanne Nelson

May 16, 2013

Cardiorespiratory fitness (CRF) appears to be a strong independent predictor of not only developing 2 common cancers, but also the prognosis.

The risk of developing both lung and colorectal cancer were decreased by 68% and 38%, respectively, in men with the highest levels of fitness, as compared with those who were the least fit, according to a new study.

A high level of fitness was also associated with a 14% reduction in cancer-specific mortality (hazard ratio [HR], 0.86; P < .001), and a 23% reduction in cardiovascular-specific mortality (HR, 0.77; P < .001).

"It is well accepted that fitness is a powerful way to predict cardiovascular disease and survival, even above other risk factors including self reported physical activity, said lead study author Susan Lakoski, MD, assistant professor of medicine at the University of Vermont, in Burlington."Unfortunately, little is known about fitness as a predictor of cancer incidence and subsequent outcomes in patients who develop cancer."

"This is important to identify robust predictive markers as its becoming increasingly necessary as cancer incidence is projected to increase over the next 2 decades," said Dr. Lakoski. "Patients are now expected to live sufficiently long to be at risk for non–cancer related mortality, specifically cardiovascular disease."

Dr. Lakoski presented the findings of her research at a press briefing held in advance of the 2013 annual meeting of the American Society of Clinical Oncology® (ASCO).

Few studies have examined the prognostic importance of CRF in relationship to cancer incidence or cause-specific mortality following a cancer diagnosis in men. In the current study, Dr. Lakoski and colleagues evaluated the association between CRF and the incidence of prostate, lung, or colorectal cancer in men, and subsequent cause-specific mortality among men who had received a cancer diagnosis.

The cohort included 17,049 men (mean age, 50 years) who had received a single cardiovascular fitness assessment as part of a specialized preventive health check-up visit that was offered at the Cooper Institute, in Dallas, Texas. Performance was recorded in established units of fitness called metabolic equivalents (METs). The participants were then separated into 5 quintiles according to their fitness performance.

Medicare claims were then subsequently analyzed to identify the participants who had developed lung, colorectal, or prostate cancer. The mean times from their initial CRF assessment to cancer incidence and death were 20.2 ± 8.2 years and 24.4 ± 8.5 years, respectively. During this time period, a total of 2885 men were diagnosed with prostate, lung, or colorectal cancer (2332 with prostate cancer, 276 with colorectal cancer, and 277 with lung cancer).

Within the study period, a total of 769 men died of all-cause mortality, with 347 of those deaths due to cancer, and 159 to cardiovascular disease.

"Fitness did not significantly impact prostate cancer risk," Dr. Lakoski said. "The data was also adjusted for risk factors such as body weight and age."

Compared with men in the lowest CRF quintile, the adjusted hazard ratio for lung, colorectal, and prostate cancer incidence among men in the highest CRF quintile was 0.32 (95% confidence interval [CI], 0.20 - 0.51; P < .001), 0.62 (95% CI, 0.40 - 0.97; P = .05), and 1.13 (95% CI, 0.97 - 1.33; P = .14), respectively. For men who developed cancer, cancer-specific mortality and cardiovascular-specific mortality decreased across increasing CRF quintiles (P values < .001).

For example, even a small improvement in fitness levels (1-MET increase in CRF) was associated with a 14% reduction in cancer-specific mortality (HR, 0.86; 95% CI, 0.81 -  0.91; P < .001) and a 23% reduction in cardiovascular-specific mortality (HR, 0.77; 95% CI, 0.69 - 0.85; P < .001).

Everyone Can Benefit

The study authors also found that that even if the men weren't obese, those who had low fitness had an increased risk for cancer and cardiovascular disease.

Fitness is a strong independent predictor of incident lung and colorectal cancer in men, and also a robust predictor of cause-specific mortality in middle-aged and older men diagnosed with lung, prostate, or colorectal cancer, Dr. Lakoski concluded. "These findings provide support for the utility of fitness testing in the preventive healthcare settings to determine cancer risk and prognosis after cancer."

This is one of the first studies to establish CRF as an independent and strong predictor of cancer risk and prognosis, commented ASCO President Sandra M. Swain, MD, FACP. "A really interesting finding is that even if men aren't obese, they can still have an increased risk of cancer even if they're not fit."

"This suggests that everyone can benefit from improving their fitness," said Dr. Swain, who served as a comoderator of the briefing.

This research was supported by the National Cancer Institute. Coauthor Jeffrey M. Peppercorn, MD, MPH, reports relationships with GlaxoSmithKline, Bayer, and Genentech.

2013 Annual Meeting of the American Society of Clinical Oncology: Abstract 1520. Will be presented June 2, 2013.

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