Shelby Scott, M.D., FACSM, FAAFP, is part-time faculty at Natividad Medical Center in Salinas, CA, and associate clinical faculty at University of California-San Francisco School of Medicine. She practices Family Practice and Sports Medicine in the Santa Cruz area of California.
Although heart disease is the number one cause of death (COD) in the United States, cancer is more feared by most Americans. This may be with good reason too. According to the Department of Health and Human Services, the incidence of cancer is increasing. In 2006, one in every four deaths in the United States was due to cancer (1). Awareness of heart disease and its causes and prevention have been in the forefront of public health since the 1960s. As a result, the percentage of deaths caused by heart disease has decreased. During the same period, the percentage of total deaths attributed to cancer has increased. If the trend continues, within the next 10 years, cancer may surpass heart disease as the leading COD (Table 1) (1).
There are many different types of cancer, but all cancers are defined as uncontrolled growth and spread of abnormal cells. If the growth of these abnormal cells remains uncontrolled, the result is death. Cancers result from a combination of external and internal forces. External, or environmental, forces include tobacco, carcinogenic (or cancer-causing) chemicals, radiation, and various types of infection. Internal, or intrinsic, causes of cancer include mutations to the cellular deoxyribonucleic acid strands or the proteins controlling their replication, hormones and hormone receptors, genetic susceptibility factors, and metabolic mutations (1).
The National Cancer Institute estimates that the lifetime risk of developing cancer is approximately 50% for men and 34% for women (1). In 2002, combined cancer-related deaths surpassed cerebral vascular accidents as the number two COD (5). There are 1,500 cancer-related deaths every day. Lung cancer is the number three COD; and colon cancer, the number five COD in the United States. The rates of various cancers, like lung and breast cancers, are increasing (3). Breast cancer is the number one cause of cancer-related death for Hispanic women and the second leading cause of cancer-related deaths for White, Black, Asian, and Native American women (3).
The National Institutes of Health estimated the cost of cancer in the United States in 2005 at $209.9 billion. Most of this cost is from lost work production ($17.5 billion) and premature death of a productive community ($118.4 billion). Approximately 75% of cancers are diagnosed in people older than 55 years (1). As the age of the working public increases, the amount of productivity lost will increase. Therefore, it becomes increasingly important to prevent cancer and improve screening to facilitate earlier treatment.
According to the American Cancer Society (ACS), cancers related to cigarette smoking and alcohol consumption are totally preventable. In 2006, there were 170,000 preventable tobacco-related cancer deaths. One in every three of the 564,830 cancer deaths in 2006 were due to poor nutrition, decreased physical activity, and overweight or obesity. All these deaths were preventable with education about proper diet and activity. Approximately 35% of cancer is attributed to dietary factors; and 30%, to cigarette smoking. One million squamous and basal cell skin cancers could have been prevented with use of sun protection. Other cancers related to hepatitis B virus (HBV), human immunodeficiency virus (HIV), human papillomavirus (HPV), and Helicobacter pylori infections could be prevented with lifestyle changes, education, immunizations, and antibiotic treatment (Table 2) (1). In 1996, the ACS added regular physical activity to the list of recommended preventive measures.
There are many studies demonstrating the link between decreased physical activity and cancer (1,7-9). Sedentary jobs are associated with a 60% increased risk of colon cancer (9,10). Men who exercise 1 to 2 hours a day have a 50% decrease in colon cancer. The Harvard University study of 48,000 professional men controlled for dietary factors including fiber intake and found that physical activity alone lowers risk of colon cancer (10). Similar studies have demonstrated that a sedentary lifestyle is associated with increased risk of breast and uterine cancer for women and prostate cancer for men (9,11).
The American College of Sports Medicine, ACS, and the American Heart Association recommend at least 30 minutes of brisk physical activity-above usual physical activity-on five or more days per week to reduce the risk of various types of cancers (1,12). Increasing to 45 to 60 minutes of exercise further reduces the risk of colon and breast cancers. Activity recommendations extend to children and adolescents. There is an increasing trend of overweight and obesity in young people, thereby increasing their lifetime risk of cancer. To counter this trend, the ACS recommends at least 60 minutes of moderate-to-vigorous physical activity at least 5 days of the week (11). Previously sedentary men older than 40 years or women older than 50 years or people with cardiovascular risk need to consult with a physician before starting a new exercise program. The same is true for sedentary people with chronic medical conditions.
Dietary changes are important for prevention because of the link between overweight and obesity and cancer (7,8,11). Increased calorie intake and weight gain are associated with increased circulating insulin and hormone levels. Hormones are associated with the regulation of growth and replication of different cell types; excessive levels may lead to increased growth of abnormal cells. Eating five servings of fruits and vegetables each day is important. Besides increasing dietary fiber, fresh fruits and vegetables contain cancer-fighting antioxidants, vitamins, and minerals. Properly prepared fruits and vegetables are usually lower in calories than processed foods, helping to control weight. Eating more whole-grain foods and less processed and red meats helps to reduce risk of colon cancer (9,11).
Another simple measure to prevent cancer is the use of proper sun protection. More than one million squamous and basal cell skin cancers can be prevented every year with the use of sunscreen and by limiting sun exposure. Simple vaccinations for HPV and HBV vaccines can prevent cancer. Proper treatment of H. pylori and HIV infections can prevent other cancers.
Screening also is important in both cancer prevention and early treatment. Cancer-related costs of indirect morbidity (time lost for illness) and direct mortality demonstrate the need for early diagnosis and effective treatment. Currently, more than 17% of Americans younger than 65 years do not have any health insurance, and many more lack adequate coverage. Of Americans older than 65 years, 25% have Medicare insurance only (1). Although there are screening tools for many types of cancer, the lack of adequate health care coverage prevents many from being screened. Another obstacle is the lack of education about the need for screening.
The U.S. Centers for Disease Control and Prevention (CDC) provides funding for screening programs and community education to increase awareness of cancer prevention and facilitate early treatment (Table 3) (5,8). The National Breast and Cervical Cancer Early Detection Program provides 6.5 million screening and diagnostic breast examinations for low-income women every year. It pays for breast examination, mammogram, and Papanicolaou screening with participating providers. Screen for Life: National Colorectal Cancer Action Campaign promotes screening for colorectal cancer in low-income individuals older than 50 years. The program is only available to people in a few states but is evaluating barriers to proper screening nationwide. The CDC has a lung cancer initiative to prevent and control tobacco use, especially in young people. Because there is no screening test for lung cancer, it is very important to prevent starting and promote smoking cessation. The Division of Nutrition and Physical Activity has a national campaign-Promote a Healthy Diet: 5 a Day-to reduce risk of cancer by encouraging people to eat five or more fruits or vegetables a day. Other CDC funding includes programs for prostate (Prostate Cancer Screening: A Decision Guide) and skin (Guidelines for School Programs to Prevent Skin Cancer) cancers.
In summary, more than one third of all cancers can be prevented. Increased physical activity can prevent many forms of cancer. Tobacco avoidance, cessation of smoking, weight loss, and other lifestyle modifications can further reduce cancer risk. Appropriate screening can diagnose some common forms of cancer early, facilitating cancer treatment and extending productive life.
1. American Cancer Society. Cancer Facts and Figures-2006
. Atlanta: American Cancer Society, 2006.
6. Grulich, A.E., M.T. van Leeuwen, M.O. Falster, et al. Incidence of cancers in people with HIV/AIDS compared with immunosuppressed transplant recipients: a meta-analysis. The Lancet
10. Neiman, D.C. The Exercise-Health Connection
. 1st ed. Champaign: Human Kinetics, 1997.
12. Haskell, W.L., I.M. Lee, R.R. Pate, et al. Physical activity and public health: updated recommendation for adults from the American College of Sports Medicine and the American Heart Association. Circulation