Scientists estimate that more than 60 percent of cancer deaths in the United States are preventable through lifestyle changes. Although there is no certain way to avoid all cancers, reducing individual risk factors significantly decreases the likelihood of contracting many forms of this devastating disease.

Lifestyle Changes

The ACS estimates that smoking causes nearly 30 percent of all cancer deaths in the United States—that is, approximately 166,000 cancer deaths each year. All cancer deaths caused by tobacco smoking could be prevented completely by not smoking and not using smokeless tobacco. For those who already smoke, quitting will reduce the risk of developing cancer. Studies show that after about ten years of not smoking, a past smoker’s risk lowers to about the level of those who have never smoked.
After quitting smoking, eating a healthy diet is the best way to lower the risk of cancer. Certain foods have been found to protect against cancer. Among these foods are broccoli, cauliflower, cabbage, tomatoes, soy products, and foods high in vitamins A, C, and E. In addition, green and possibly black teas contain compounds that protect the body from carcinogens. These foods contain substances called antioxidants that block the action of free radicals. Other chemicals in fruits and vegetables are thought to block the cell growth promoting effects of steroid hormones, protecting against cancers of the breast and prostate.
To lower cancer risk, diets should include little or no red meat. Other foods to avoid or consume in moderation include sugar, saturated fat from animal products, and salt. Added fats and oils should come from vegetables, such as olives or corn, rather than from animal sources. Carbohydrates should come from whole grains, such as brown rice and whole wheat bread, rather than from processed foods, such as white rice and white bread.
The risk of cancer of the esophagus increases with heavy alcohol consumption, and many studies suggest that consuming alcoholic beverages increases the risk of breast cancer as well. Studies show that limiting intake to two drinks a day for men, and one drink per day for women, reduces cancer risk.
Low levels of physical activity have been implicated in colon cancer. Moderate activity for 30 minutes a day enhances the immune system, shortens the time food takes to move through the intestines, and alters body composition and hormone levels. Researchers are studying how these effects might lower cancer risk. Physical activity also helps avoid obesity, which is associated with an increased risk for cancers of the colon and rectum, prostate, breast, endometrium, and kidney. By maintaining a healthy weight through regular physical activity and a healthy diet, individuals can substantially lower their risk for these cancers.
Protecting the skin from the sun’s rays could prevent about 80 percent of all skin cancers. When in the sun for prolonged periods, always wear sunscreen with a sun protection factor (SPF) of 15 or greater, particularly if you have fair skin or freckles. Skin needs protection every day, not just on sunny days. The Skin Cancer Foundation also recommends that people avoid the sun at its peak (from 10 am to 4 pm), seek shade, and cover up with clothing and a brimmed hat.
People also can help prevent cancer by practicing safe sex or abstaining from sex. The human papilloma virus (HPV) linked to cervical cancer is the most common cancer-causing virus in the United States. Minimizing the number of sexual partners, using condoms, or practicing sexual abstinence reduces risk of infection with HPV. Infection with the human immunodeficiency virus (HIV), also sexually transmitted, greatly increases an individual’s risk for cancers of the immune and lymphatic system, such as Kaposi’s sarcoma. Infection with the hepatitis B virus (HBV) is the predominant cause of liver cancer in the United States. HBV is transmitted from person to person through unprotected sexual intercourse with an infected person, or through the sharing of infected needles or other sharp instruments that break the skin. Vaccination against hepatitis B reduces the spread of this virus, which leads to reduced incidence of liver cancer.

Screening and Early Detection
Double-Contrast Barium X Ray of the Large Intestine
Detecting cancer in its early stages significantly improves a patient’s chances for survival. The American Cancer Society recommends that symptom-free patients undergo a number of regular screening tests. One such test, a double-contrast barium enema, is used to detect colorectal cancer. Barium, an X-ray opaque material or contrast medium, makes intestinal tumors and other defects stand out as dark spots against the brighter healthy intestinal tissue in X rays. The American Cancer Society recommends people over age 50 have a double-contrast barium enema every 5 to 10 years.

The next best thing to lifestyle changes is early detection to prevent cancer from becoming life threatening. Detecting a tumor while it is still in an early stage is the best predictor of long-term survival. For this reason, the ACS recommends a number of screening tests for people who do not have symptoms. A cancer-related checkup is recommended every three years for people aged 20 to 40 and every year for people over age 40. For more information about other screening tests, see the table on Cancer Screening Recommendations.
In addition to regular cancer check ups, advanced technologies may help detect certain cancers. Scientists have developed tests for the presence of certain genetic mutations. People who test positive for these genetic mutations may take preventive measures such as more frequent cancer screening examinations and dietary modification to reduce their risk. Women who test positive for a mutated breast cancer gene, such as BRCA1 or BRCA2, may choose to have a mastectomy even when no cancer is present. This eliminates most breast tissue before cancer has a chance to form.
The ability to determine a person's genetic risk for cancer years or even decades before it develops has raised a number of ethical, social, and psychological implications. Several government committees have published guidelines to prevent discrimination in hiring or firing employees who have had a genetic test or have tested positive for a particular cancer-causing gene. Families with high risk for cancer are also affected by the psychological implications of knowing which family members are at risk and which are not. In some cases, tests are available to identify people at risk for certain cancers, such as inherited forms of breast or colon cancers, but surefire preventive or treatment measures for these cancers have not been developed yet. While some people would prefer to know their risk for disease so they can make appropriate lifestyle changes, others prefer not to be hampered by this knowledge when no treatment exists for the problem.
Sixty percent of people diagnosed with cancer now survive more than five years. Between 1990 and 1995 cancer incidence and death rates dropped for the first time in 20 years. In 1998 the ACS, the NCI, and the Centers for Disease Control and Prevention (CDC) confirmed that cancer rates are still on the decline. In the past 40 years, the death rate from cancer in children has dropped 62 percent. These improved cancer statistics are due in part to behavioral and lifestyle changes, but equal credit goes to the advances in cancer research that have taken place in the last three decades.

Clinical Trials

Clinical trials are research studies that use human patients to determine if a new treatment is effective. Medical and ethical panels overseen by the Food and Drug Administration (FDA) carefully review the research methods and ethics of a clinical trial before the trial begins, then monitor the trial throughout its four main phases. Phase I of a clinical trial studies a small number of patients to determine the best dosage and delivery method of a new drug treatment. Patients who participate in a Phase I trial usually have advanced cancer and would not be helped by other known treatments. Phase II, conducted with a different group of patients, determines how well the treatment actually works in different types of cancer. Phase III compares the effectiveness of the new treatment in one set of patients to another set of patients who receive the best currently available drug treatment. In Phase IV studies, the treatment becomes part of the standard treatment regimen, but it is tested for how effective it is when combined with other treatments.
Researchers continually study and find new ways to treat cancer. Studies in an area of research called antimetastasis focus on halting tumor cells from spreading and invading new tissues. Other researchers study how to stop a tumor from developing its own blood supply, a process called antiangiogenesis. Two antiangiogenesis drugs, called angiostatin and endostatin, stop the growth of blood vessels and have been quite successful in treating tumors in mice. These two drugs are currently in clinical trials in humans.
Several drugs that block oncogene signals are in clinical trials. Researchers are also introducing genes into immune cells that will specifically recognize and kill cancer cells. Other research is investigating the introduction of a normal gene into a tumor cell to increase the tumor's sensitivity to chemotherapeutic drugs.
A growing field of cancer prevention research is chemoprevention, or the use of natural or synthetic compounds to decrease the number of mutations that may lead to cancer. Chemoprevention research seeks to identify those compounds that reduce risk and use them in pills or food additives as a prevention measure for those who are at high risk for cancer. More than two dozen chemopreventive compounds are currently being studied for how well they work in humans.

Basic Research

Scientists who conduct basic research on the causes of cancer focus on the fundamental genetic mutations that underlie cancer. One goal seeks to identify all of the mutations present in a patient’s tumor, enabling better prediction of the tumor’s future behavior. Developing technologies use a tiny glass chip the size of a computer chip to compare DNA in tumor cells to DNA in healthy cells. This new diagnostic tool will someday help physicians to tailor the treatment of individual patients according to their tumors’ genetic makeup.
Since cancer is uncontrolled cell division, research into the genetic mechanisms that control normal cell division also holds promise. A better understanding of the normal function of a mutated gene may provide better insight into what goes wrong in tumor cells. This may lead to better treatments designed to combat specifically the effects of the mutation.
Contributed By:Karen R. Peterson

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