Liz Meszaros, MDLinx | March 13, 2019
In men, higher cardiorespiratory fitness may be associated with a lower incidence of lung cancer and, in those with lung cancer, reduced mortality and longer survival, according to results from a study published in the Journal of Science and Medicine in Sport. Based on these results, possible future public health strategies to prevent lung cancer and its consequences could include screening, early detection, and intervention for low cardiorespiratory fitness.
Researchers undertook this prospective study to assess the associations between cardiorespiratory fitness and the incidence of lung cancer and lung cancer mortality in men.
“Despite the fact that smoking increases the risk for lung cancer about 25-fold, the majority of cigarette smokers do not develop lung cancer and thus there may be other factors besides smoking that modify the risk. Mounting evidence has firmly established that low cardiorespiratory fitness (CRF) is an important risk factor for the incidence of many chronic conditions as well as all-cause and cardiovascular mortality,” wrote the authors, led by Baruch Vainshelboim, PhD, assistant professor, Master of Cancer Care Program, School of Health Sciences, Departments of Cancer Care and Physical Therapy, Saint Francis University, Loretto, PA.
Dr. Vainshelboim and colleagues included 4,920 men (mean age: 59.2 years; 58% Caucasian; 20.6% African American; 8.7% Hispanic; 8.3% Asian) from the Veterans Exercise Testing Study who were free from any malignancies. At baseline, 29.3% were current smokers, and 34.1% had a history of smoking. They followed subjects for a mean of 12.7 years.
In all, 2.1% of the men developed lung cancer during follow-up, and 79% of them died from cancer a mean of 3.6 years after diagnosis. Subjects who received a diagnosis of lung cancer were older, more likely to currently smoke, and had lower baseline cardiorespiratory fitness levels.
Researchers found that cardiorespiratory fitness was inversely and independently associated with cancer outcomes. For every 1-MET increase in cardiorespiratory fitness, they found a 10% reduction in the incidence of lung cancer and a 13% reduction in cancer mortality. For those with moderate cardiorespiratory fitness, there was an associated 47% reduction in lung cancer incidence and a 58% reduction in cancer mortality. Finally, in subjects with high cardiorespiratory fitness, they found a 65% reduction in the incidence of lung cancer and a 76% reduction in cancer mortality (P=0.002 for all comparisons).
Significantly longer survival was seen in subjects who had a diagnosis of lung cancer but had moderate or high cardiorespiratory fitness at baselines compared with those with low baseline cardiorespiratory fitness (P < 0.001). Population attributable risk (PAR) percentages were 8.7% for the incidence of lung cancer and 18.5% for cancer mortality (P=0.001 for both).
“Participants diagnosed with lung cancer who had moderate or high [cardiorespiratory fitness] CRF levels at baseline exhibited a longer survival time compared to those with low CRF. In addition, the results suggest that by eliminating the risk factor of low CRF, 8.7% of lung cancer incidence and 18.5% of cancer mortality in those diagnosed with lung cancer could potentially be prevented,” noted Dr. Vainshelboim and colleagues.
They also stressed the importance of these results in public health efforts to prevent lung cancer.
“Given that lung cancer is one of the most prevalent cancers with a 5-year survival of only 10%–17%, the current findings have important public health implication for primary and secondary prevention of lung cancer. In particular, screening, early detection and treating low [cardiorespiratory fitness] could be a potentially important strategy for prevention programs, which aligns with the recent recommendation of the American Heart Association to adopt [cardiorespiratory fitness] as a vital sign,” they concluded.