Page 8 Complete Your CE Test Online - Click Here The International Agency for Research on Cancer (IARC) classifies the ethanol in alcoholic beverages as a Group 1 Carcinogen, meaning that it is known to be carcinogenic to humans. The IARC further notes that acetaldehyde, which is produced in the body after consuming alcohol, is known to be carcinogenic as well. The U.S. National Toxicology Program also lists alcoholic beverages as known carcinogens, although acetaldehyde is still on its list of “reasonably anticipated to be human carcinogens.” The American Cancer Society recommends that people who drink should do so in moderate amounts. Their intake maximums agree with the U.S. Federal government’s Dietary Guidelines for Americans, which defines moderate alcohol drinking as up to one drink per day for women and up to two drinks per day for men. They further define a standard drink as 12 ounces of beer, 5 ounces of wine, or 1.5 ounces of 80-proof liquor. All of these serving sizes contain about 0.6 of an ounce of pure ethanol. Researchers have identified multiple ways that alcohol may increase the risk of cancer: ● ● Metabolizing ethanol acetaldehyde, which is a toxic chemical; acetaldehyde can damage both DNA and proteins. ● ● Generating reactive oxygen species (chemically reactive molecules that contain oxygen), which can damage DNA, proteins, and lipids through a process called oxidation. ● ● Impairing the body’s ability to break down and absorb a variety of nutrients that may be associated with cancer risk, including vitamin A; nutrients in the vitamin B complex, such as folate; vitamin C; vitamin D; vitamin E; and carotenoids. ● ● Increasing blood levels of estrogen, a sex hormone linked to the risk of breast cancer. Some alcoholic beverages may also contain a variety of carcinogenic contaminants that are introduced during fermentation and production, such as nitrosamines, asbestos fibers, phenols, and hydrocarbons. It has been suggested that certain substances in red wine, such as resveratrol, have anticancer properties. However, there is no evidence that drinking red wine reduces the risk of cancer. What happens to cancer risk after a person ceases drinking alcohol? Most of the studies that have examined whether cancer risk declines after a person ceases drinking alcohol have focused on head and neck cancers and on esophageal cancer. In general, these studies have found that stopping alcohol consumption is not associated with immediate reductions in cancer risk; instead, it may take years for the risks of cancer to return to those of never-drinkers. For example, a pooled analysis of 13 case-control studies of cancer of the oral cavity and pharynx combined found that alcohol-associated cancer risk did not begin to decrease until at least 10 years after stopping alcohol drinking. Even 16 years after they stopped drinking alcohol, the risk of cancer was still higher for ex-drinkers than for never drinkers. In several studies, the risk of esophageal cancer was also found to decrease slowly with increasing time since alcohol drinking cessation. A pooled analysis of five case-control studies found that the risk of esophageal cancer did not approach that of never drinkers for at least 15 years after alcohol drinking cessation. Drugs Exogenous hormones Estrogens, a group of female sex hormones, are known human carcinogens. Although these hormones have essential physiological roles in both females and males, they have also been associated with an increased risk of certain cancers. For instance, taking combined hormone therapy to reduce menopause symptoms (estrogen plus progestin, a synthetic version of the female hormone progesterone) can increase a woman’s risk of breast cancer. Menopausal hormone therapy with estrogen alone increases the risk of endometrial cancer and is used only in women who have had a hysterectomy. A woman who is thinking about menopausal hormone therapy should understand the possible risks and benefits before she starts taking it. After the cancer connection was identified, doctors began to prescribe it only for bothersome menopausal symptoms in low doses and for the shortest possible lengths of time. Studies have also shown that a woman’s risk of breast cancer is related to the estrogen and progesterone made by her ovaries (endogenous estrogen and progesterone). Being exposed for a long time or to high levels of these hormones has been linked to an increased risk of breast cancer. Increases in exposure can be caused by early menarche, late menopause, being older at first pregnancy, and never having given birth. Conversely, having given birth is a protective factor for breast cancer. On the other hand, the risk of ovarian cancer decreases with longer years of having taken oral contraceptives. Diethylstilbestrol (DES) is a form of estrogen that was given to some pregnant women in the U.S. between 1940 and 1971 to prevent miscarriages, premature labor, and related problems associated with pregnancy. DES came in many forms, including pills, creams, and vaginal suppositories. Women who took DES during pregnancy may have an increased risk of breast cancer, as may their daughters. Their daughters (“DES daughters”) have an increased risk of a cancer of the vagina or cervix. DES daughters should have annual pap smears from the vagina and cervix, and follow up any abnormalities with colposcopy. The National Cancer Institute recommends that DES daughters rigorously follow the routine breast cancer screening recommendations for their age group. The possible effects on the sons and grandchildren of women who took DES during pregnancy are still being studied. Other drugs There are a number of other drugs on the American Cancer Society combined list of known carcinogens. Adriamycin, alkylating agents, azacitidine, busulfan, CCNU, chlorambucil, chlorozotocin, cisplatin, cyclophosphamide etoposide, melphalan, nitrogen mustard, procarbazine, semustine, and tamoxifen and are some of the cancer treatment drugs that have made the list so far. As with radiation therapy, there are safety trade-offs; a low risk of a possible second cancer in the future is a risk worth taking to most people facing the much more immediate threat of death from existing cancer. Phenacetin, chloral hydrate, chloramphenicol, pioglitazone, and cyclosporine are drugs on the known carcinogen list that are not designated for cancer treatment. Infectious agents Certain infectious agents can cause cancer in infected people or increase the risk that cancer will form. Some viruses can disrupt normal controls on cell growth and proliferation. They may also increase the chance that a person will be affected by other cancer risk factors, such as UV radiation or substances in tobacco smoke that cause cancer. Some viruses, bacteria, and parasites also cause chronic inflammation, which may lead to cancer. Most of the viruses that are linked to an increased risk of cancer can be transmitted through blood or other body fluids. People can lower their risk of infection from many of these by getting vaccinated, not having unprotected sex, and not sharing needles or equipment if they inject drugs. Globally, infectious agents have been estimated to cause 18% of all cancer cases. The burden of cancers caused by infections is much greater in developing nations (26%) than in developed nations (8%). Human papillomaviruses (HPVs) Infection with high-risk types of human papillomavirus (HPV) causes nearly all cervical cancers. Infection with an oncogenic strain of HPV is considered a necessary event for later development of cervical cancer, and vaccine-conferred immunity (available to younger people before sexual initiation) results in a marked decrease in precancerous lesions. Oncogenic strains of HPV also cause most anal cancers and many oropharyngeal, vaginal, vulvar, and penile cancers. In the U.S., the Advisory Committee on Immunization Practices (ACIP) recommends that children aged 11 to 12 receive an HPV vaccine series that helps to prevent infection with the types of HPV that cause most HPV-associated cancers. Children as young as age 9 and adults as old as 26 can also be vaccinated. If an infectious agent is a cause of cancer, then effective anti-infective interventions would be expected in most instances to be effective cancer prevention interventions. This is the expectation with vaccines that protect against infection with oncogenic strains of HPV.