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Established, Modifiable Cancer Risk Factors

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According to a new American Cancer Society report published by Gapstur et al in CA: A Cancer Journal for Clinicians, the highest priority in a national cancer control plan is the expansion of tobacco control—the intervention with the largest potential health benefits. This report is the second in a series of articles that together inform priorities for a comprehensive cancer control plan.

Led by Susan M. Gapstur, PhD, MPH, American Cancer Society Senior Vice President of Behavioral and Epidemiology Research, the report focuses on several important modifiable risk factors.

Tobacco

More than half of the 26% decline in cancer mortality rates in the United States since 1991 is due to reductions in tobacco smoking. Despite this progress, tobacco smoking (active and second-hand smoke) remains the most common cause of cancers diagnosed (19.4%, n = 304,880 [year 2014]) and cancer death (29.6%, n = 173,670 [year 2014]). Moreover, the annual direct health-care costs of tobacco in the United States are estimated to be $170 billion, and tobacco use results in $156 billion in lost productivity.

There is considerable evidence that tobacco control can prevent more cancer deaths than any other primary prevention strategy. The demographic profile of today’s smoker has changed over the past half century. Enhanced efforts to reach groups that are more likely to smoke are needed to further reduce the prevalence of tobacco use.

Obesity and Overweight

In the United States, approximately, 7.8% of cancer cases in 2014 were attributed to excess body fatness, second only to cigarette smoking. Its contribution was higher among women (10.9% of cases) than among men (4.8% of cases). Among women, 60.3% of uterine cancer and, among men and women combined, more than 30% of gallbladder, liver, and kidney/renal cancers as well as esophageal adenocarcinoma were attributed to excess body fatness. Despite clear evidence that excess body fatness contributes substantially to cancer risk, the full impact of the obesity epidemic on the cancer burden, including the long-term effect of obesity that begins in childhood, is yet to be completely understood.

Alcohol

Alcohol is the third most-important major modifiable contributor to cancer, associated with 6.4% of cancers in women and 4.8% of cancers in men in 2014. However, for some cancers, the attributable fraction exceeds 10%; among men and women combined, an estimated 40.9% of oral cavity/pharynx cancers, 23.2% of larynx cancers, 21.6% of liver cancers, 21% of esophageal cancers, and 12.8% of colorectal cancers were attributed to alcohol consumption. Notably, among women, alcohol intake accounted for 16.4% of all cases, or 39,060 breast cancers in 2014.

Diet

The combination of low calcium, fiber, and fruit and vegetable intake and high red and processed meat intake is estimated to cause 4.2% of cancers among men and women combined. However, there was considerable variation across specific dietary factors and types of cancer. For example, 5.4% of colorectal cancers are associated with high red meat consumption causes, 8.2% with high processed meat consumption, and 10.3% and 4.9% for low dietary fiber and calcium consumption, respectively. Low fruit and vegetable consumption was attributed to 17.6% and 17.4% of oral cavity/pharynx and larynx cancers, respectively. A lack of clear evidence about the role of early life dietary exposures as well as many other dietary hypotheses means the percentage of cancers attributable to diet may continue to rise beyond current estimates once more is known.

Physical Inactivity 

It is estimated that 2.9% of all cancer cases in the United States in 2014 were attributable to low physical activity, with the contribution greater among women (4.4%) than among men (1.5%). The cancer with the highest percentage related to low physical activity was uterine cancer (26.7%), followed by colorectal cancer (6.3% among men and women combined). As additional cancer types are determined to be causally associated with low amounts of physical activity, the total number of cancer cases attributed to low physical activity will continue to rise.

“A comprehensive cancer control plan designed to support the implementation of evidence-based interventions, including cancer prevention interventions like those we described, has enormous potential to substantially reduce the number of individuals diagnosed with and dying from cancer,” said Dr. Gapstur in a statement. “It is the responsibility of government and industry as well as the public health, medical, and scientific communities to work together to invest in and implement a comprehensive cancer control plan at the national level and support and expand ongoing initiatives at the state and local levels. If we fail to do so, we will slow progress in our national efforts to reduce the burden of cancer.”

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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