Fitness levels linked to lung, colorectal cancer risk, outcomes
High levels of cardiorespiratory fitness appeared associated with reduced risk for lung and colorectal cancer, as well as lower risk for death after diagnosis with these cancers, according to study results published in Cancer.
“Our findings are one of the first, largest and most diverse cohorts to look at the impact of fitness on cancer outcomes,” Catherine Handy Marshall, MD, MPH, assistant professor in the department of oncology at Johns Hopkins University School of Medicine, said in a press release. “Fitness testing is commonly done today for many people in conjunction with their doctors.”
In the retrospective cohort study, Handy Marshall and colleagues evaluated 49,143 consecutive adults (median age, 54 years; 46.1% women; 63.9% white; 29.3% black: 0.7% Hispanic) who participated in clinician-referred exercise stress testing between 1991 and 2009. The researchers limited the study to cancer-free adults aged 40 and 70 years who were treated within the Henry Ford Health System in Detroit.
Researchers collected clinical history from data available at the time of testing and/or through electronic medical records. They obtained information about age, sex, smoking history, height and weight at the time of the stress test.
Cardiorespiratory fitness was measured in metabolic equivalents of task (METs), with participants classified according to levels less than 6 (reference), 6 to 9, 10 to 11, and 12 or greater.
The researchers acquired information on incident cancer through linkage with the Henry Ford Cancer Institute tumor registry, and accessed all-cause mortality using the National Death Index. They used Cox proportional hazard models to separately evaluate correlations between cardiorespiratory fitness and lung and colorectal cancer.
Incident lung cancer and colorectal cancer served as the study’s primary outcomes. All-cause mortality from the stress test date among those diagnosed with lung or colorectal cancer served as the secondary outcome.
Median follow-up was 7.7 years.
The Cox proportional hazard models, adjusted for age, race, BMI, smoking history and diabetes, revealed that participants with the highest fitness level (METs 12) had a 77% lower risk for lung cancer (HR = 0.23; 95% CI, 0.14-0.36). These participants also had a 61% lower risk for colorectal cancer (HR = 0.39; 95% CI, 0.23-0.66), with further adjustment for aspirin and statin use.
Those subsequently diagnosed with lung cancer who were in the highest fitness tier had a 44% decreased risk for death (HR = 0.56; 95% CI, 0.32-1), whereas those at the highest fitness level who were diagnosed with colorectal cancer had an 89% reduced risk for death (HR = 0.11; 95% CI, 0.03-0.37).
Fitness testing may be useful in assessing risk for these cancers, as well as for other diseases, according to Handy Marshall.
“Many people might already have these results and can be informed about the association of fitness with cancer risk in addition to what fitness levels mean for other conditions, like heart disease,” she said in the press release. – by Jennifer Byrne
Disclosures: Handy Marshall reports a grant from the Conquer Cancer Foundation from Bristol-Myers Squibb for study-related work, a consultant role with McGraw-Hill and travel fees from Dana Oncology for work performed outside of the current study. Please see the study for all other authors’ relevant financial disclosures.