Fitness reduces risk of lung cancer, death from cancer
BY WILL PASS
MDedge News
A high level of cardiorespiratory fitness (CRF) is associated with a significantly lower risk of lung cancer, based on a retrospective analysis involving almost 50,000 patients.
Fitter individuals were also less likely to die during follow-up, reported lead author Catherine Handy Marshall, MD, of Johns Hopkins University in Baltimore, and colleagues.
Fitter individuals were also less likely to die during follow-up
“[T]here are limited data to date regarding the relationship between CRF and cancer incidence and mortality,” the investigators wrote (Cancer. 2019 May 6. doi: 10.1002/cncr.32085). Prior studies have reported an inverse relationship between CRF and incidence of lung cancer, and cancer mortality; however, these previous study populations lacked diversity, the investigators noted.
“To the best of our knowledge, the current study is the largest cohort with exercise fitness testing and the first study to include females to address this question,” the investigators wrote.
The study involved 49,143 patients referred for exercise stress testing within the Henry Ford Health System in Detroit during 1991-2009. Patients were aged 40-70 years and were cancer free. The exercise stress test measured CRF in units of metabolic equivalents of task (METs), with scores grouped into four categories, from least fit to most fit: less than 6, 6-9, 10-11, and 12 or higher. After stress testing, patients were followed for cancer through May 2010 using the Henry Ford Cancer Institute tumor registry. If cancer was diagnosed in a patient during this follow-up period, the investigators cross-referenced the Social Security Death Master File to check for subsequent death. Primary outcomes were lung cancer and colorectal cancer. For those diagnosed with these diseases, the secondary endpoint was all-cause mortality. Multivariable model adjustments incorporated a variety of other patient factors, such as age and sex; comorbidities, such as diabetes and hypertension; and, where applicable, relevant treatments and medications. About two-thirds of patients were white (64%), about one-third were black (29%), and a small percentage were Hispanic (1%). Slightly fewer than half were female (46%).
Data analysis after a median of 7.7 years of follow-up showed that the fittest patients had a 61% decreased risk of colorectal cancer and a 77% decreased risk of lung cancer, compared with least fit individuals. For lung cancer, this decreased risk held consistent throughout all subgroups by smoking status, race, and sex. In contrast, highly fit women and black patients did not show decreased risks of colorectal cancer, compared with least fit individuals in the same subgroups; however, the investigators suggested cautious interpretation of these findings because of the relatively small sample sizes and suggested that other factors may be at play.
For lung cancer, this decreased risk held consistent throughout all subgroups by smoking status, race, and sex.
Compared with least fit patients, when highly fit individuals were diagnosed with colorectal or lung cancer, they had an 89% and 44% decreased risk of dying during follow-up, respectively.
The investigators pointed out that the reported relationships between high fitness and lower risks of lung and colorectal cancer and subsequent death were consistent with previous studies.
“The results of the current study support the idea that clinically obtained cardiac stress testing provides important additional information regarding cancer risk and mortality after cancer diagnosis in a general, clinically referred population,” the investigators wrote. “The protective effect observed could be due to the positive effects of fitness, including improved respiratory function, decreased bowel transit time, better immune function, or reductions in systemic inflammation for example, which is an active area of research.”
The protective effect observed could be due to the positive effects of fitness, including improved respiratory function, decreased bowel transit time, better immune function,
The investigators concluded their article with a look at the road ahead.
“Future research is needed to determine whether this association is similar in the general population and to determine whether improving fitness can influence cancer and mortality rates,” the investigators wrote. “In addition, patients who undergo stress testing also should be counseled regarding the importance of the results to their cancer risk and mortality, not just their cardiovascular risk.”
The study was funded by Bristol-Myers Squibb through the Conquer Cancer Foundation Young Investigator Award. The investigators reported relationships with McGraw-Hill, Dava Oncology, AstraZeneca, Pfizer, and others.
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