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Fitness may affect risk of colorectal cancer and survival likelihood after diagnosis

Fri, 05/03/2019 - 10:07
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Adults who were the most fit had the lowest risk of developing colorectal and lung cancer, and among individuals who developed lung or colorectal cancer, those who had high fitness levels before their cancer diagnosis were less likely to die compared with those who had low fitness levels. The findings, ‘Cardiorespiratory Fitness and Incident Lung and Colon Cancer in Men and Women: Results from the Henry Ford Exercise Testing (FIT) Cancer Cohort’, were published in Cancer, a peer-reviewed journal of the American Cancer Society.

According to the study’s authors, the relationship between cardiorespiratory fitness (CRF) and lung and colorectal cancer outcomes is not well established. To investigate, Dr Catherine Handy Marshall of Johns Hopkins School of Medicine, and her colleagues studied 49,143 adults who underwent exercise stress testing from 1991-2009 and were followed for a median of 7.7 years.

The patients ranged in age from 40 to 70 years, were without cancer, and were treated within the Henry Ford Health System in Detroit, Michigan. CRF, measured in metabolic equivalents of task (METs), was categorized as <6 (reference), 6 to 9, 10 to 11, and ≥12. Incident cancer was obtained through linkage to the cancer registry and all‐cause mortality from the National Death Index.

Participants had a mean age of 54±8 years. Approximately 46% were female, 64% were white, 29% were black, and 1% were Hispanic. The median follow‐up was 7.7 years. The study represents the largest of its kind, as well as the first of its kind to involve women and a large percentage of non-white individuals.

Cox proportional hazard models, adjusted for age, race, sex, body mass index, smoking history, and diabetes, found that those in the highest fitness category (METs ≥12) had a 77% decreased risk of lung cancer (hazard ratio [HR], 0.23; 95% CI, 0.14‐0.36) and a 61% decreased risk of incident colorectal cancer (HR, 0.39; 95% CI, 0.23‐0.66; with additional adjustment for aspirin and statin use). Among those diagnosed with lung and colorectal cancer, those with high fitness had a decreased risk of subsequent death of 44% and 89%, respectively (HR, 0.56 [95% CI, 0.32‐1.00] and HR, 0.11 [95% CI, 0.03‐0.37], respectively).

"Our findings are one of the first, largest, and most diverse cohorts to look at the impact of fitness on cancer outcomes," said Marshall. "Fitness testing is commonly done today for many people in conjunction with their doctors. 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."

Additional studies are needed to expand on these results and to determine if improving fitness can influence risk and mortality rates of cancer.