New Orleans, LA—If you cannot get your patients with lung cancer to stop smoking, at least encourage them to exercise. That is the message from research conducted on a large cohort of individuals in the Third National Health and Nutrition Examination Survey (NHANES III), which showed that markers of inflammation were significantly reduced among men with lung cancer who smoke, if they exercised.
These important findings were presented at the 2016 American Association for Cancer Research annual meeting by Marisa A. Bittoni, PhD, Research Scientist, Ohio State University Comprehensive Cancer Center, Columbus.
“Our results are in line with those of our [previous] prospective cohort study, which showed substantial reductions in lung cancer deaths (30% to 50%) from increased physical activity and healthier eating, primarily in smokers and males,” Dr Bittoni said. “The theory was that smokers with lung cancer had more of an inflammatory environment, because of the smoking.”
However, little effect was observed among women, especially nonsmokers, she added.
Inflammation and Cancer
Chronic inflammation is associated with adverse lifestyle factors, including poor diet, lack of physical activity, and smoking. Systemic inflammation plays an important role in carcinogenesis for several cancers, including lung cancer. C-reactive protein (CRP) is a protein that is elevated in response to acute inflammation, infection, and tissue damage. CRP levels have been shown to be moderately elevated in persons with chronic inflammatory diseases, including cancer, the researchers noted.
The purpose of this study was to simultaneously examine the associations between lifestyle factors and CRP levels, and to look for differences according to smoking and sex, Dr Bittoni said.
NHANES III
Data from cancer-free individuals aged >40 years in NHANES III (1988-1994) were examined to assess potential relationships between exercise patterns, dietary habits (measured by the Healthy Eating Index), and inflammation.
The researchers identified 5405 persons with normal CRP levels (<3 mg/L), and 3545 with elevated CRP levels (≥3 mg/L).
Elevated CRP levels were more likely among smokers than nonsmokers (56.5% vs 53.6%; P <.0001), and in people with poor diets compared with those with healthy diets (35.7% vs 31.7%; P <.0001).
On a multivariate analysis, smoking raised the risk for elevated CRP levels by 41% (P <.0001), and exercise reduced the risk by 22% (P = .0001).
Other types of physical activity were also significantly related to lower CRP levels, but walking had the strongest association. On a univariate analysis, the odds ratio (OR) for walking 1 mile within the past 30 days was 0.43.
Dr Bittoni acknowledged that walking for 1 mile in the past month is not a very strenuous definition of physical activity, but she suggested that a “yes” answer may identify people who tend to exercise more regularly.
With regard to other lifestyle factors, the OR estimates for selenium remained similar and statistically significant in all groups (P <.05). The ORs for serum vitamin D levels (0.90) and Healthy Eating Index scores (0.92) were only significant for male smokers.
The greatest effect on CRP levels, she reiterated, was seen with walking, “which was out-doing healthy eating” as a means of reducing inflammation.
Reduction in inflammation is important, Dr Bittoni said. “Inflammation is part of the tumor microenvironment. If you reduce inflammation, you reduce the chance of getting cancer. Anything that does that should be helpful,” she emphasized.
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