Cardiorespiratory Fitness, Lung Cancer Incidence, and Cancer Mortality in Male Smokers.

INTRODUCTION: The preventive role of cardiorespiratory fitness in lung cancer among smokers is unknown. This study aims to evaluate the association between cardiorespiratory fitness and lung cancer incidence and cancer mortality in former and current male smokers.

METHODS: From 1987 to 2014, cardiorespiratory fitness (quantified from treadmill exercise testing) was assessed in 2,979 men (former smokers, n=1,602; current smokers, n=1,377) aged 59.1 (SD=17.4) years and prospectively followed up for 11.6 (SD=7) years. Multivariable Cox hazard models and population attributable fraction of low cardiorespiratory fitness (<5 METs) for cancer outcomes were analyzed during 2018.

RESULTS: Of the 99 case patients diagnosed with lung cancer, 79 died of cancer 3.6 (SD=4.6) years after diagnosis. Among former smokers, 1-MET increase and categories of moderate and high cardiorespiratory fitness were associated with 13% (p=0.016), 51%, and 77% (p-trend=0.015) reductions in lung cancer incidence, respectively. Among current smokers who were later diagnosed with lung cancer, 1-MET increase and categories of moderate and high cardiorespiratory fitness were associated with 18% (p=0.008), 84%, and 85% (p-trend<0.001) reductions in cancer mortality, respectively. The population attributable fraction for lung cancer incidence was 10.8% among former smokers and 22.3% for cancer mortality among current smokers.

CONCLUSIONS: Higher cardiorespiratory fitness is associated with lower risk of lung cancer incidence in former smokers and reduced risk of cancer mortality in current smokers who were diagnosed with lung cancer. Screening for low cardiorespiratory fitness and achieving at least moderate cardiorespiratory fitness could potentially reduce lung cancer morbidity and mortality, providing a preventive strategy for smokers.