About 42 percent of all cancer cases and roughly 45 percent of cancer deaths in the United States are attributable to modifiable risk factors, said Susan Gapstur, PhD, senior vice president of behavioral and epidemiology research for the ACS. Dr. Gapstur detailed the evidence regarding modifiable cancer risk factors in a seminar hosted by Wiley Science Talks. While some risk factors are well-known, such as the link between smoking and lung cancer, studies are revealing a range of lifestyle habits and behaviors that influence a range of cancer types. Public health officials are focused on four risk factors that appear to have the biggest influence on cancer development: Tobacco, alcohol, excess weight, and lack of exercise. RELATED: Metastatic Non-Small-Cell Lung Cancer: Finding the Right Care for You
Smoking: Not Just a Risk for Lung Cancer
Worldwide, smoking is responsible for about 71 percent of lung cancer deaths and about 22 percent of all cancer deaths, according to a study published in October 2016 in The Lancet. Tobacco usage has been linked to around 15 different types of cancer, including oral cancers, cancers of the lung, liver, stomach, bowel, and ovaries, and some types of leukemia, according to the Union for International Cancer Control (UICC). Quitting at any age is deemed helpful to reduce cancer risk. Within five years of quitting smoking, an individual’s chance of developing cancer of the mouth, throat, esophagus, and bladder is cut in half, according to the Centers for Disease Control and Prevention (CDC). Ten years after quitting, the chances of developing lung cancer is reduced by half. More effort should be made to help smokers quit, Gapstur said. RELATED: Smoking Increases Risk for Depression and Schizophrenia, Study Suggests
Alcohol: Many People Are Unaware That It Raises Risk for Cancer
Cancers associated with alcohol use include head and neck cancer, esophageal cancer, liver cancer, breast cancer, and colorectal cancer, according to the National Cancer Institute (NCI). In women, about 6.4 percent of all cancer cases are attributable to alcohol use, Gapstur said, adding. “It accounts for more than 16 percent of all cases of female breast cancer.” Moderate to heavy use increases the risk most dramatically, but even light drinkers (no more than one drink a day) have a modest increase in the risk of some cancers, according to the NCI. Moreover, a study published in the American Journal of Public Health showed that about 3.5 percent of cancer deaths in the United States are alcohol-related. Despite these statistics, Gapstur said, public awareness on the link between cancer and alcohol use is low, “even among healthcare providers,” Gapstur said. Moreover, she said, cancer control plans often leave out alcohol as a modifiable risk factor. RELATED: San Antonio Breast Cancer Symposium: New Therapies for Women With HER2-Positive Breast Cancer Highlighted on Day 1
Excess Body Weight: Second Only to Smoking as a Cancer Risk
In the past 20 years, more evidence has emerged that excess body weight and obesity contribute to several types of cancer, Gapstur said. An estimated 7.8 percent of U.S. cancer cases are linked to excess body fat — a risk factor that is second only to tobacco usage in its effect on cancer development. More than 65 percent of U.S. adults are overweight or obese. “We can now conclude that excess body weight increases the risk of 13 types of cancer,” she said. The strongest links between being overweight and developing cancer are for endometrial cancer and adenocarcinoma of the esophagus. An estimated 60 percent of cases of endometrial cancer can be attributed to excess body weight. Evidence is also emerging linking particular types of foods to cancer risk, she said. For example, red meat and low dietary fiber is associated with an increased risk of colorectal cancer. RELATED: The Link Between Stress and Obesity
Physical Activity: Reduces Inflammation and Regulates Hormones
The lack of physical activity and the obesity epidemic go hand-in-hand, said Gapstur. According to the NCI, exercise lowers cancer risk by reducing inflammation, improving immune system function, regulating hormones in blood that contribute to cancer risk, speeding food digestion (which reduces exposure to dietary carcinogens in the gut), and reducing body fat. An earlier meta-analysis of 52 epidemiologic studies that examined the association between physical activity and colon cancer risk, published in the British Journal of Cancer, found that the most physically active individuals had a 24 percent lower risk of colon cancer compared with those who were the least physically active. RELATED: Can Exercise Prevent Some Types of Cancer?
Other Risk Factors Play a Role
Experts are also focusing on a range of other modifiable risk factors for cancer. These include:
Ultraviolet Radiation UV radiation from the sun or tanning beds increases the risk of all types of skin cancer.Workplace Hazards This can include exposure to asbestos and some chemicals.Viruses Viruses such as human papillomavirus (HPV), the Helicobacter pylori virus (H. pylori), and hepatitis B (HBV) are responsible for about 16 percent of all cancers worldwide, according to the UICC. Vaccines are available to reduce infection with hepatitis B and HPV, thus reducing the risk of liver cancer associated with hepatitis B and several types of cancers linked to HPV (cervical, anal, penile, and oral cancers).
RELATED: New AAD Guidelines Address Best Practices for Preventing and Treating Basal Cell and Squamous Cell Skin Cancer
Decreasing Cancer Risk — a Complex Task
Effort will be required by policy makers, from the federal government to local communities, to address modifiable cancer risks, Gapstur said. “We live in a very complicated society where we have many demands on our time, and gaining access to healthy environments is a challenge,” she said. “This is really going to involve a comprehensive approach at changing multiple sectors in order to allow people to have access to information as well as to live in healthier environments.” Information and help should be tailored to specific communities, she added, noting that some groups are more affected by cancer than others. “People with lower education and lower incomes as well as people facing mental health challenges are far more likely to use tobacco,” she said. Sometimes, people simply don’t know they are increasing their risk of cancer, Gapstur said. For example, studies suggest that only about 25 to 40 percent of people know that alcohol use can drive up cancer risk. Healthcare professionals should do more to help people who have risks that can be addressed, she said. For example, “More than 65 percent of smokers want to quit. Each year more than 50 percent attempt to quit. Conversations about cessation must be part of routine primary care,” Gapstur said. Well-known strategies, such as taxing cigarettes, can prompt some people to quit. Medical groups and policy makers are also trying new strategies, such as banning alcohol advertisements on city buses, trains, and train stations, and, recently, a law passed by Congress to raise the minimum age to purchase tobacco products to age 21. RELATED: E-cigarettes Raise Risk of Chronic Lung Disease, Long-Term Study Finds
