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The scientific basis and rationale for cancer prevention continues to grow and will likely continue to gain momentum. Ob/gyns have enthusiastically embraced cancer screening, sometimes known as secondary prevention. Widespread cervical screening has led to a striking decline in cervical cancer. Breast and colon cancer screening also generally have been incorporated into our practices. Adoption of primary cancer preventive approaches, however, has been less widespread. Our specialty is not unique in this respect and the lack of reimbursement for many preventive services is a significant barrier.
Prevention ultimately may be the most efficient means of reducing cancer incidence. The old adage, "an ounce of prevention is worth a pound of cure," sums up this issue exceedingly well. In my opinion, ob/gyns should be more proactive about offering cancer prevention strategies.
A look back at developments in the 20th century provides evidence of the importance of cancer prevention, which is underscored by dramatic changes in cancer incidence and mortality ascribable to avoidingor not avoidingchemical carcinogens. Take, for example, the use of iceboxes for refrigeration, which were so named because they employed large blocks of ice. Because iceboxes were not very efficient, large amounts of nitrates were added to foods as preservatives. Carcinogenic metabolites of these nitrates strikingly increase the incidence of stomach cancer, which in years past was a leading cause of cancer mortality. Since the introduction of electric refrigerators, nitrate use has decreased and rates of stomach cancer have fallen dramatically. Stomach cancer has gone from being a common killer to a rare entity in the United States.
In contrast to this stunning success story, lung cancer stands out as our society's greatest failure to avoid a chemical carcinogen. Its primary cause, smoking, is an addictive habit that took hold with a vengeance in the 20th century. As smoking gained popularity, lung cancer death rates skyrocketed, and now the disease is the leading cause of cancer deaths in the US. Women initially lagged behind men until they gained equal rights, including the right to smoke. Only recently has lung cancer incidence finally begun to decline.
Ironically, because smoking is associated with earlier menopause, the risk of endometrial cancer is lower in smokers. But in the final analysis, estimates indicate that about half of all cancers worldwide are attributable to tobacco.
Despite the magnitude of the tobacco-associated cancer problem, as ob/gyns, we tend to have blinders on and to narrowly focus our attention on reproductive tract and breast cancers. Let me give you an example from my own personal experience. One of my special interests as a gynecologic oncologist is hereditary ovarian cancer. Genetic testing for mutations in BRCA1 and 2 facilitates prophylactic oophorectomy in high-risk women and we can now prevent about 5% to 10% of these highly lethal cancers. Although this is an important advance, it is easy to lose sight of the fact that there are many more deaths each year from lung cancer than all gynecologic cancers combined.
So, smoking cessation is at the top of my PDA "to do" list for the 21st century. Because smoking involves a chemical addiction to nicotine as well as psychologic dependence, it is not realistic to expect people to stop on their own. Formal smoking cessation programs involving counseling, emotional support, and pharmacologic agents such as nicotine and bupropion are much more effective. Despite the proven efficacy of cessation programs, many insurance companies do not cover these services. I hope this shortsighted approach will change in the future as health-care systems move toward more preventive approaches. Of course, the best preventive approach of all is to ensure that young adults don't become addicted to tobacco to begin with.
Many busy clinicians, myself included, often rationalize that it is "not in our job description" to address tobacco abuse. We are too busy. But consider this: In addition to increased cancer risks, tobacco takes a high toll in cardiovascular and lung disease. "It is difficult to identify any other condition that presents with such a mix of lethality, prevalence, and neglect despite effective and readily available interventions," states the Public Health Service document, Treating Tobacco Use and Dependence, ( http://www.surgeongeneral.gov/tobacco/systems.htm ). Sadly, a recent survey found that only 15% of smokers who saw a physician were offered assistance with quitting and only 3% were given a follow-up appointment to address this issue. So are we truly serving women well if we ignore this health issue? All of us should strongly advise smokers to quit. In addition to discussing the health consequences of smoking, ob/gyns and their nurses should take every opportunity to refer patients to smoking cessation programs.
Diet is the second key cancer prevention opportunity. I believe that in 20 years the typical American diet will be regarded with the same scorn we now reserve for smoking. Unfortunately, as was the case with smoking, there is usually a considerable lag between scientific evidence of harm and actual change in behavior. From the scientific standpoint, it is now abundantly clear that the average American diet can be characterized as carcinogenic! The biggest issuebut by no means the only oneis the total amount of calories we consume from fat and processed carbohydrates. This is best illustrated by "fast food" restaurants that offer "super sizes" and "biggie fries" and "biggie shakes." We have an epidemic of obesity in this country, which not only increases the incidence of cardiovascular disease but also contributes significantly to cancer deaths.
A link between fat intake, body weight, and cancer has long been suspected in cancers of the breast, colon, and endometrium. In addition, it is intriguing to note that severe calorie restriction dramatically decreases cancer incidence. In April, results of the largest and most conclusive study to date addressing the issue of body weight and cancer were published.1 Begun 20 years ago, the study by the American Cancer Society (ACS) involved almost 1 million people and compared death rates from various types of cancers among individuals with normal and elevated body weights. The researchers reported that 4% of cancer deaths in men and 20% in women in the US could be attributed to obesity.
Death rates from most types of cancer were higher in individuals who were overweightincluding several types where this relationship had not previously been suspected. The proportion of cancer deaths attributable to obesity was higher in women than men, because women have a greater propensity to gain excess weight with aging. This is thought to increase cancer risk for several reasons. First, fat tissue produces estrogens, which are known to increase reproductive tract cancers, and the risks of breast, uterine, cervical, and ovarian cancer were all increased. The greatest rise in relative risk was seen for uterine cancer: Overweight women were more than sixfold more likely to develop the disease. In addition to increased hormone levels, high caloric intake is associated with excess production of growth factors. Not only do these substances stimulate the body to grow, but they also have been shown to enhance the development and growth of cancer cells. Finally, because the ACS study focused on cancer mortality rather than incidence, the higher rates observed in the obese may have been partly attributable to the challenges inherent in treating these patients.
How do you determine if a patient is overweight to an extent that will increase her risk of cancer? From a practical standpoint, a relatively simple way to assess whether one is above ideal body weight is to go to the ACS home page to calculate body mass index (BMI) http://www.cancer.org/docroot/PED/ped_3.asp?sitearea=PED . A normal BMI is under 25, which in a 5 ft 5 in woman corresponds to less than 150 lb. People who are overweight with a BMI in the 25 to 30 range (150 to 210 lb for the 5 ft 5 in woman) have modestly increased rates of cancer mortality, whereas those who are obese and have a BMI over 30 have the highest cancer mortality.
Like smoking, obesity is a problem that is better avoided, in this case, by consuming a balanced diet that lacks excess fat and carbohydrates. In contrast to smoking cessation programs, which are effective but frustratingly underemployed, it remains to be seen whether any specific obesity regimen is better than another because of the poor success rates with weight-loss programs. The obesity epidemic has spawned a mega-industry of diets, exercise programs, and surgical options, such as the now-popular bariatric surgery. Antiobesity molecules discovered as a result of the genomics revolution are the therapeutic hope of the future.
Because obesity disproportionately affects women, ob/gyns should take an active role in combating this problem. In addition to giving patients with information on appropriate dietary guidelines at different stages of their reproductive lives, we should increase our familiarity with the various approaches to treating obesity. Although a major reduction in the fraction of women who are morbidly obese will likely depend on changes at a societal level that are beyond a physician's control, ob/gyns and their staffs should be prepared to offer patients referral to reputable weight-loss programs.
The other "carcinogenic" feature of the American diet is its low fruit, vegetable, and whole grain content. This is a critical issue because these foods are the main source of antioxidant vitamins, fiber, and other natural substances that prevent colon and other types of cancers. A huge industry has developed that promotes the virtues of vitamin pills and other supplements. However, we do not understand the complex array of substances in Mother Nature's fruits and vegetables well enough to distill their benefits into a pill. Many people believe that they can eat a lousy diet and make up for it by taking vitamins, but vitamins have only proven beneficial when consumed as part of the foods that comprise a healthy diet.
Although folate in pregnancy and vitamin D and calcium after menopause are accepted preventive interventions for neural tube defects and osteoporosis, respectively, the value of vitamin pills and other supplements for cancer prevention and treatment are unproven. In some cases, there may be a narrow window between recommended daily amounts of vitamins and potentially harmful levels. For example, there is now concern that vitamin A supplements may increase the risk of osteoporosis. Fortunately, the National Cancer Institute is now sponsoring studies that will allow us to draw scientific conclusions regarding vitamins and cancer prevention.
Although smoking and obesity are not typically considered a "bread and butter" part of obstetrics and gynecology, these issues have a great impact on cancer risk and general health. As we strive to fulfill our mission of improving the health of American women, serious consideration should be given to increasing the level of awareness and education regarding smoking and diet. More emphasis on these topics is needed in our residency training programs and in continuing medical education activities. We should increasingly come to appreciate that cancer prevention and the overall health of our patients is best guided by the adage "an ounce of prevention is worth a pound of cure."
Andrew Berchuck. Editorial: An ounce of cancer prevention really is worth a pound of cure. Contemporary Ob/Gyn Aug. 1, 2003;48:8-12.