Although there is appropriate focus on finding cures for cancer, most cancers could be prevented with currently available programs. Public health progress is essential to winning the war on cancer.
Cancer is far more easily prevented than cured. Primary prevention works through reduction in risk factors and changes to the environment, especially reducing tobacco use. The World Health Organization's MPOWER package outlines effective action to protect people against tobacco.
Cancer can also be prevented by reducing alcohol consumption through policies such as alcohol taxes and limits on alcohol sales, and by restoring caloric balance through policies such as creating healthier food environments and engineering the built environment to increase opportunities for physical activity.
Vaccination is an effective approach to preventing specific virus‐associated cancers, such as human papillomavirus vaccine to prevent cervical and oropharyngeal cancer and hepatitis B virus vaccine to prevent hepatocellular cancer.
Secondary prevention reduces cancer mortality through screening and early treatment; this approach has been used successfully for breast and cervical cancer and is particularly underused against colon cancer.
Progress can be made in all three approaches to cancer prevention, but will require a greater emphasis on public health programs and public policy. Winning the war on cancer will require a much larger investment in prevention to complement efforts to improve treatment.
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Ever since 1971, when the United States declared a "War on Cancer", and even before, there has been appropriate fear and focus on defeating cancer. Siddhartha Mukherjee's fantastic book, Emperor of All Maladies, recounts the biography of cancer.
Although there has been progress in the past 50 years, cancer remains a leading cause of death, particuarly among younger people. What's particularly tragic is that many means to reduce cancer are readily available, but not being implemented.
First and foremost is tobacco control. Tobacco causes about one third of all deaths from cancer. The MPOWER package outlines what's needed to reduce tobacco use.
Of the main interventions for tobacco control, taxation is the most important. Countries could end the tobacco epidemic by taxing, increasing tax enforcement with a track and trace approach, fully funding comprehensive tobacco control, and by regulating the nicotine content in combustible tobacco down to non-addictive levels and allowing use of controlled-dose non-combustible nicotine as this is done.
Alcohol causes nearly 4% of the global cancer burden. Daily alcohol consumption, even in low amounts, can enhance carcinogenesis. Chronic heavy alcohol use is associated with cancers of the oral cavity, larynx, pharynx, esophagus, liver, colon, rectum, and breast.
Many public policy options exist for alcohol control. Alcohol availability can be reduced through various regulations, and as with tobacco control, taxes can increase the price of alcohol, the social environment can be altered to discourage consumption, and assistance can be provided to those with or at risk for problem drinking.
Obesity is associated with a higher incidence of many cancers, including cancers of the endometrium, kidney, gallbladder (in women), breast, colon, and esophagus. It has been estimated that, in the U.S., if the prevalence of overweight and obesity was reduced, some 90,000 cancer deaths could be prevented every year.
Obesity has more than doubled in the U.S. in the past 25 years. Human genes have not changed rapidly enough to cause this epidemic; changes in diet and physical activity over the past few decades are to blame. These changes are caused by the transformation of the modern environment. A public health approach to obesity must alter the environmental context for healthy eating and increased physical activity.
An international review estimated that increased fruit and vegetable consumption could prevent 5%–12% of the worldwide cancer burden, and 20%–30% of upper gastrointestinal cancers. Specific dietary patterns may also be associated with greater risk from, or protection against, certain cancers.
Certain viral infections are proven to cause cancer, and vaccination against these viruses can prevent cancers from developing. Cervical cancer and hepatocellular cancer are strongly linked to infection with human papilloma virus (HPV) and hepatitis B virus (HBV), respectively. There is increasingly strong evidence of the association of many oropharyngteal cancers with HPV as well. Prevention of both these virus‐associated cancers rests on strong government policies and programs to ensure high levels of vaccination coverage in entire populations. These include broad‐based rather than targeted recommendations about who should be vaccinated, vaccination mandates enforced at the time of school entry, government subsidies that offer vaccination at reduced or no cost, and convenient provision of vaccines.
HPV can be detected in virtually every case of cervical cancer. More than 20 million people in the U.S. are currently infected with this sexually transmitted infection, with 6.2 million people infected annually. The HPV vaccine protects against most oncogenic HPV.
Hepatocellular cancer, which kills about 320,000 people globally each year, is believed to be attributable in about 80% of cases to viral hepatitis, particularly HBV. Infants infected perinatally have a 90% risk of developing chronic HBV infection, whereas <5% of those infected at ≥5 years of age will develop chronic infection. The risk of developing hepatocellular cancer is 100 times higher among those with chronic HBV infection.
Many countries attempt to vaccinate all infants against HBV, a practice that has contributed to dramatic declines in HBV prevalence. It is also important to provide postexposure prophylaxis to infants born to hepatitis B surface antigen–positive women.
Screening is responsible for important progress in cancer prevention, reducing mortality from cancers of the breast, cervix, skin, colon, and possibly prostate. Yet screening for colon cancer, the second leading cause of cancer death in the U.S., lags. Although detecting colorectal cancers when still localized results in a 90% survival rate, most are not diagnosed at these early stages. Mammography and Papanicolaou testing have achieved much higher coverage in their respective target populations.
Patients are also reluctant to undergo colonoscopy or sigmoidoscopy because it is a complex procedure that requires uncomfortable preparation. Many interventions to increase screening rates have been devised, some with significant success; a patient navigator system in three New York City hospitals increased screening volumes by 50%, and overall colonoscopy screening rates increased from 42% to 60% between 2003 and 2006.
As with infectious disease control in the past century, public health strategies that implement a range of interventions can have a dramatic effect reducing cancer. It's time to greatly strengthen prevention, especially primary prevention, to the paradigm of cancer control, and to recognize that prevention requires not just medical care but also strong public health and primary care systems and effective public policy.
