Preventing Cancer

Preventing cancer is much better than trying to find ways to treat it after it has occurred. Cancer prevention has much to do with identifying and avoiding risk factors that may trigger the disease. Most cancers take a long time to develop, and the way people take care of their bodies may help determine their susceptibility to cancer. However, experts do not agree about many supposed risks for cancer, leaving many people unsure of what to avoid and what precautions to take. Still, educating oneself about proven risks is a necessary strategy if one is to avoid or overcome the disease.

Control of Risk Factors

Some cancer risk factors cannot be controlled. Age—the single most important risk factor for cancer—is one over which people have no control. More than half of all cancers occur in older people. The other risk factor beyond human control is heredity. People cannot choose the genes they inherit. Although cancer caused by inherited genes is infrequent, if a certain type of cancer has occurred in close relatives, a person may opt to have more frequent screenings or to undergo genetic tests. But beyond these two uncontrollable risk factors, most proven risk factors can be avoided or controlled.

Tobacco

In 1982 the surgeon general of the United States reported that cigarette smoking was the major cause of cancer deaths in the country. This statement is still true. Experts estimate that one-third of all cancer deaths are caused by the use of tobacco. The American Cancer Society reports that most lung cancer deaths are caused by smoking. Smoking is also a major cause of cancers of the larynx, throat, oral cavity, esophagus, and bladder. It also contributes to the development of cancers of the pancreas, cervix, kidney, stomach, and some leukemias.

Cigarette smoke contains dozens of chemical carcinogens, and it can harm nearly every organ in the body. In addition to cancer, it causes heart disease and other serious illnesses. Smoking costs billions of dollars in health care each year. It is the most avoidable environmental cause of cancer, yet Americans still light up. Every two years the federal government conducts a Youth Risk Behavior Survey of students in grades nine through twelve. The survey tracks a variety of risk behaviors, including drug, alcohol, and tobacco use. In June 2008 the results of the latest survey showed that one out of every five students in the survey smoked cigarettes regularly.

Experts agree that choosing “light,” “low-tar,” or “mild” cigarettes does not reduce the health risk associated with smoking.

When Smoking Was In

Until late in the twentieth century, cigarette smoking was more in the public eye. In the early days of TV, many newscasters used cigarettes as sophisticated props. There were clever ads for smoking on TV, and magazines were filled with colorful full-page ads for different brands of cigarettes. Cigarette companies even advertised in medical journals. During World War II, the government regularly issued cigarettes to everyone in the armed forces. In movies, leading characters often smoked, making the habit seem glamorous to viewers.

Today, the trend has been reversed. Laws have banned cigarette advertising on billboards and in public venues frequented by children. Several states have antismoking laws in restaurants, malls, and other public places. On television, smoking has been banned since 1971, but it persists in movies. In July 2008, however, six major studios announced plans to include antismoking announcements on millions of DVDs of motion pictures that include smoking. The main force behind these bans and announcements has been the U.S. surgeon general's persistent warning that smoking is linked to several ailments, including cancer. The surgeon general first made this public pronouncement in 1964, and, overnight, smoking became less a matter of personal choice than an issue of public health.

There is no such thing as a safe cigarette. Cigar smoking is also associated with cancers of the lip, tongue, mouth, and throat as well as of the lung. Like cigarette smokers, cigar smokers who start early in life and smoke most often are at the greatest risk.

Chewing tobacco contains twenty-eight carcinogens. It is sometimes called “spitting” tobacco because people spit out the tobacco juices that combine with saliva and build up in their mouths. In 1986 the surgeon general concluded that the use of smokeless tobacco “is not a safe substitute for smoking cigarettes. It can cause cancer and a number of noncancerous conditions and can lead to nicotine addiction and dependence.”⁶

Secondhand Smoke

A person does not have to be a smoker to be at risk for harm caused by tobacco smoke. Secondhand smoke is smoke released from the end of a lit cigarette or cigar or smoke exhaled by a smoker. Nonsmokers who are exposed to secondhand smoke absorb nicotine and other toxic chemicals just as smokers do. The U.S. Environmental Protection Agency (EPA) and the International Agency for Research on Cancer (a branch of the World Health Organization) have classified secondhand smoke as a “known human carcinogen.”⁷

The 2006 U.S. surgeon general's report reached the conclusion that secondhand smoke causes lung cancer and that there is no safe level of exposure to secondhand smoke. The report said that ventilating buildings and separating smokers from nonsmokers is not enough to protect nonsmokers. It recommended banning all smoking in buildings and spaces where smokers and nonsmokers are together.

Children are especially sensitive to secondhand smoke. Even if they don't live in a home with a regular smoker, they can be exposed to secondhand smoke in public places such as shopping centers, public transportation, and restaurants. For adults, the workplace is a major source of secondhand smoke exposure. Today, more and more nations are enacting clean indoor air laws to protect people from secondhand smoke.

Ultraviolet (UV) Rays

Skin cancer is the most common of all types of cancer. Most skin cancers are caused by exposure to too much ultraviolet (UV) radiation from the sun or tanning beds.

It is estimated that more than 1 million new cases of skin cancer occur each year. In recent decades, the rates of all kinds of skin cancers have been increasing. Certain people are more susceptible to skin cancer. This high-risk group includes those who work outside, like to sunbathe, use a tanning bed, have a family history of skin cancer, are fair skinned, or have a lot of moles.

Basal and squamous cell skin cancers are the most common varieties. They are also referred to as non-melanoma skin cancers to differentiate them from the more deadly form of skin cancer called melanoma. Basal and squamous cell skin cancers appear mainly on parts of the body exposed to the sun. They seldom spread, but if left untreated they can grow quite large and invade and destroy nearby tissues.

Melanoma is responsible for 77 percent of all skin cancer deaths, but if it is caught and treated early, the cure rate is about 95 percent. Melanoma can spread to major organs such as the lungs, the liver, and the brain. For 2008 the National Cancer Institute estimated a total of more than sixty-two thousand new cases of melanoma in the United States and more than eight thousand deaths from it. Many of those deaths could be prevented if everyone were aware of the warning signs of skin cancer and took precautions to protect their skin cells from damage by excessive UV rays.

Three important warning signs people should watch for are:

• Spots that grow in size and do not heal
• Moles that grow, itch, or change shape or color
• Bleeding sores that do not go away

Commonsense preventive measures include:

• Limiting exposure to the sun between 10 a.m. and 4 p.m.
• Wearing broad-brimmed hats while outdoors in the sun
• Wearing tightly woven protective clothing while outdoors in the sun
• Using a waterproof sunscreen with a sun protection factor (SPF) of 15 or higher
• Staying out of tanning beds
• Having a doctor check any suspicious-looking skin lesions

Radon Gas

Radon, an invisible, odorless gas, is the leading cause of lung cancer among nonsmokers in America. The Environmental Protection Agency says it claims about twenty-one thousand lives annually. Radon, which is produced from the natural decay of uranium, is found in nearly all soils. Radon moves up through the ground to the air above and into houses through cracks and holes in the foundations. The house then traps radon inside. Over time, the radon can accumulate to high levels.

Dangerous Research

Working as a team in France, Pierre and Marie Curie were husband-and-wife scientists who spent much of their lives investigating radiations given off by radioactive substances. From tons of uranium ore, they isolated small amounts of two highly radioactive new chemical elements, naming them radium and polonium. In 1903 they were awarded the Nobel Prize in Physics for their work. When Pierre died suddenly in an accident three years later, Marie carried on with their research. In 1911 she received the Nobel Prize in Chemistry.

During World War I, Marie, with the help of her daughter Irene, worked on X-rays for medical diagnosis in the treatment of wounded soldiers. After the war, Marie continued her research in radiation therapy, for which she won international acclaim. When she became ill with leukemia and died, Irene and her husband carried on with the work. Like her mother, Irene became ill with leukemia and died from it in 1956 in the Curie Hospital in Paris.

The EPA estimates that about one in every fifteen homes in the United States has dangerous radon levels. Kristy Miller, spokeswoman for the EPA's Office of Radiation and Indoor Air says, “You can't touch it, you can't feel it. It is an inert gas. It's in your home for a long time, leaving no trail of evidence. It's only your proactive interest and testing that's going to prevent this health risk.”⁸

Relatively inexpensive radon test kits are sold at hardware stores, and some local health departments sell them at cost to homeowners. If high levels of radon are discovered, a radon contractor can be hired to fix the problem. Some states require radon testing be done before a home can be sold, and some new homes are being built to be radon resistant.

Nuclear Radiation

Nuclear radiation has caused thousands of cancer deaths. In World War II, when atomic bombs were dropped on the Japanese cities of Hiroshima and Nagasaki, the bombs released huge amounts of nuclear radiation. Among those who survived the explosions, many were diagnosed with leukemia in the following years. There was a 50 percent increase in the number of leukemia cases in Japan from 1946 to the early 1950s.

Sadako Sasaki was two years old when the atomic bomb exploded over her home in Hiroshima. She survived to become a runner who won many races at her school. When she was eleven, shortly after winning an important race, she was diagnosed with leukemia. On October 26, 1955, a small article in the Hiroshima newspaper briefly reported her death. It said, “The death of Sadako Sasaki is the fourteenth death in Noboricho Junior High School this year. She had been sick since last fall with the atomic bomb disease. She was exposed to the atomic bomb ten years ago, and now she is gone … fourteenth death in this school … seventh grader … age twelve.”⁹

The enthusiasm for nuclear power plants as a source of energy has been dampened by fear of accidents at the plants, which can lead to deaths from cancer caused by radiation. In March 1979 the nuclear reactor at Three Mile Island in Pennsylvania experienced a major accident. To prevent a disastrous meltdown, radioactive air was pumped into the atmosphere. Conservative estimates put the number of people who died from leukemia and other cancers because of exposure to the toxic air at more than three hundred. Cleaning up the plant took more than six years and cost $1 billion.

In April 1986 there was an even more horrendous accident at the Chernobyl nuclear power plant in the Soviet Union. A reactor melted down, spewing radioactive materials over a wide area. Whole communities around Chernobyl were devastated, and the soil was so contaminated that crops could no longer be grown there. In addition to the people who were killed or injured in the accident, numerous cancer deaths have occurred over the years from the radiation. Scientists on the International Commission on Radiological Protection have said that the exact number of radiation-related cancers resulting from the Chernobyl disaster will never be known. They have, however, estimated that at least nine thousand fatal radiation-induced cancers resulted from this disaster. The accidents at Three Mile Island and Chernobyl have resulted in a greater understanding of the cancer risk of radiation and a tighter control of nuclear power.

Industrial Chemicals

People who are constantly exposed to carcinogens in their workplaces are at an increased risk for cancer. The more frequent the exposure and the higher the level of exposure, the greater the risk. Manufacturers and farmers who handle fertilizers and pesticides may be at risk. Truck drivers and tollbooth workers on busy highways are exposed to high levels of diesel exhaust. People who work as dry cleaners or furniture finishers handle solvents and other materials that are carcinogenic. So do people who work in laboratories and chemical factories. Many known carcinogens used in industries have been banned by the government, like asbestos, or regulated, like benzene, nickel, and petroleum. Federal, state, and local governments also protect public health by regulating emissions of hazardous materials that pass into air, water, and land during the manufacturing process.

Viruses

During the past two decades scientists have demonstrated that viruses do cause some cancers. Experts estimate that viruses cause about 5 percent of cancer deaths in the United States today. Certain viruses can damage the DNA and then kill the host cell, increasing the risk of cancer.

The common wart-causing human papillomavirus has been linked to many cases of cervical cancer. Other papillomaviruses are linked to skin cancer. Hepatitis B and C viruses are associated with deadly liver cancer, sometimes many years after the patient has been infected with either one. The human T-cell leukemia/lymphoma virus (HTLV) damages white blood cells called T cells and causes leukemia in adults. Cases of leukemia caused by this virus have been reported in the southeastern United States as well as in Japan, Africa, Italy, and South America.

The Epstein-Barr virus, a herpes virus that causes mononucleosis, has been linked to Burkitt's lymphoma, which is found mainly in children in Africa. It is also associated with Hodgkin's disease, which occurs most often in adolescents and young adults. The human immunodeficiency virus (HIV), well known as the cause of AIDS, is linked with non-Hodgkin's lymphoma and Kaposi's sarcoma.

Ways to prevent infections caused by these dangerous viruses are still being studied, and the concept that viruses can cause cancer is fairly new. With viruses that are sexually transmitted, like HIV and hepatitis, practicing safe sex is a good precaution. And washing hands carefully and not touching the mouth and nose is a good way to avoid germs of all kinds.

Vaccines

The use of vaccines is a preventive measure under extensive study. There are two types of cancer vaccines. One is intended to treat existing cancers, and the other is intended to prevent cancers from developing. As of mid-2008, the United States Food and Drug Administration (FDA) has licensed two vaccines to prevent viruses that can lead to cancer.

The hepatitis B virus (HBV) causes a serious disease that affects the liver. It can cause an acute short-term illness, which in some people may go on to cause a chronic long-term infection. Chronic HBV infection can be very serious indeed, leading to liver cancer and death. The Department of Health and Human Services estimates that 1.25 million people in the United States have chronic HBV infection. The department reports that a vaccine can prevent hepatitis B and the serious consequences of HBV infection, including liver cancer. Since routine hepatitis B vaccination of U.S. children began in 1991, the reported incidence of acute hepatitis B among children and adolescents has dropped by more than 95 percent.

In June 2006 the Advisory Committee on Immunization Practices (ACIP) voted to recommend Gardasil, the first vaccine developed to prevent cervical cancer (and other diseases) caused by some types of human papillomavirus. It is recommended for eleven- to twelve-year-old girls and can be given to girls as young as nine. The vaccine is recommended for young girls because ideally it should be administered before one becomes sexually active. The vaccine is given in a series of three shots over a six-month period. Studies have shown that the vaccine provides protection for at least five years, and further studies are being done to see if a booster vaccine is needed later on.

Diet and Cancer

News stories on television and in magazines and newspapers often report studies that indicate certain foods should or should not be eaten to prevent cancer. However, the American Cancer Society advises that it is not a good idea to change one's diet based on a single study or news report. The ACS has made its own studies and come up with guidelines about avoiding cancer risk factors through what people eat and drink.

With regard to drinking alcohol, the ACS reports:

Alcohol raises the risk of cancers of the mouth, pharynx (throat), larynx (voice box), esophagus, liver, and breast, and probably of the colon and rectum. People who drink alcohol should limit their intake to no more than 2 drinks per day for men and 1 drink per day for women. A drink is defined as 12 ounces of beer, 5 ounces of wine, or 1.5 ounces of 80-proof distilled spirits. The combination of alcohol and tobacco increases the risk of some cancers far more than the effect of either drinking or smoking alone.¹⁰

Metabolism is the name given to the chemical changes that are continuously going on in the body's cells. Damage to tissues in the body happens constantly as a result of oxidation (normal metabolism). Antioxidant nutrients (such as vitamins A, C, and E, and beta-carotene) neutralize potential cell damage caused by oxidation. Common fruits and vegetables contain lots of antioxidants and phytochemicals (plant-based chemicals), which have been shown to lower the risk of cancer. Clinical studies have not shown that taking vitamin or mineral supplements works in the same way as eating fruits and vegetables does. In fact, the studies show that some high-dose supplements may actually increase cancer risk. The best advice from medical experts remains to eat at least five servings of fruit and vegetables every day. So far, no research exists to demonstrate whether food labeled “organic” (grown without pesticides and genetic modification) is more effective in reducing cancer risk than the same foods produced by standard methods.

Benefits of a Plant-Based Diet

American Cancer Society guidelines say, “Research studies have found that people who routinely eat large amounts of fruits and vegetables are half as likely to develop cancer as people who don't. The foods within a plant-based diet, mostly fruits and vegetables, contain a variety of nutrients and phytochemicals—fiber and plant chemicals that protect against cancer and other diseases.”

Quoted in “Eat Well, Live Longer,” OncoLog 52, no. 1 (January 2007).

Hot dogs and most lunch meats contain nitrites, which are chemical additives used to preserve and add flavoring. Nitrites can react with chemicals in the body and change into carcinogens. Americans eat more than 20 billion hot dogs each year. A study conducted at the University of Southern California reported that eating large quantities of hot dogs might cause leukemia in children. Today, vitamin C is added to nitrite-containing meats to counteract the carcinogenic effects of nitrites.

Nutritionists say that meat should be cooked well enough to kill harmful germs. Some research, however, suggests that frying, broiling, or grilling meats at very high temperatures forms chemicals that might increase the risk of cancer. Eating excessive amounts of fat, leading to obesity, has also been linked with cancers of the breast, colon, rectum, pancreas, prostate, gall bladder, ovaries, and uterus.

Exercise and Cancer

In addition to the research currently under way to discover exactly how diet contributes to preventing cancer, studies are being done to determine the effects of being overweight and a lack of physical activity on cancer risk. In February 2001 a panel of experts met at the International Agency for Research on Cancer in Lyon, France, and concluded that being overweight and leading a sedentary lifestyle are associated with an increased risk of cancer.

The panel recommended that prevention of obesity, based on healthy eating habits and regular exercise, should begin early in life. Many studies have shown that American children are becoming increasingly obese at an alarming rate. Spending long hours sitting in front of TVs or computers and consuming lots of fried and fatty foods are major contributing factors. The ACS says: “Each year, about 550,000 Americans die of cancer; fully one-third of these deaths are linked to poor diet, physical inactivity, and carrying excess weight. Being overweight works in a variety of ways to increase cancer risk. One of the main ways is that excess weight causes the body to produce and circulate more of the hormones estrogen and insulin, which can stimulate cancer growth.”¹¹

The Sunshine Vitamin

Although too much sun can increase the risk of getting skin cancer, studies show that a limited amount of sun exposure can cut the risk of getting other cancers. A team of researchers at the University of California, San Diego, reports that a daily intake of 1,000 international units (IU) of vitamin D—an important vitamin commonly generated when sunlight strikes the skin—may decrease the risk of common cancers by 50 percent. Although some foods, such as orange juice, are now fortified with vitamin D, it is hard to get enough from a regular diet. For example, a glass of milk contains only 100 IU. The researchers recommend taking a vitamin D supplement along with eating a healthy diet and getting limited sun exposure as the best way to get enough of this important cancer protection.

Not all cancers can be prevented, but experts agree that by adopting a healthy lifestyle, people can significantly reduce their cancer risk. The Department of Health and Human Services says that the number of new cancer cases could be reduced and many cancer deaths could be prevented if everyone followed these effective cancer prevention measures:

Avoiding tobacco
Avoiding sun exposure
Improving nutrition
Increasing physical activity
Achieving optimal weight¹²