Descriptive epidemiology: In 2014, the American Cancer Society estimated 1,665,540 new cancer cases and 585,720 cancer deaths in the United States. Cancer incidence and mortality rates are higher among men than women. Furthermore, African Americans have a higher cancer mortality rate than whites, which has been a source of discussion and controversy. Some argue that inherent genetic factors account for the discrepancy, whereas others attribute the difference to an overrepresentation of poverty among African Americans and superior health care received by affluent versus impoverished groups.
The leading cancers in the United States vary slightly for men and women. The five leading cancers for men are prostate, lung and bronchus, colon and rectum, urinary bladder, and melanoma of the skin. For women, the leading cancers are breast, lung and bronchus, colon and rectum, uterine corpus, and thyroid. Americans over the age of sixty-five have an almost tenfold greater risk of developing cancer than do younger Americans. Despite an increase in overall cancer mortality rate between 1950 and 1990, mortality rates for all cancers combined have declined substantially for individuals under age forty-five. They increased in people over age fifty-five, with that increase primarily related to lung cancer deaths, but began declining in the mid-2000s.
These data seem biased and problematic, as smoking is the primary etiologic factor in lung cancer diagnoses and a leading public health issue. Excluding lung cancer from cancer death statistics implies that if lifestyle issues and behaviors relate to etiology, science is not responsible or interested in research to develop effective prevention and treatment strategies. This denies the role of social, political, and economic factors in promoting increasingly prevalent maladaptive behaviors among vulnerable members of society and is an area worthy of aggressive debate and action in terms of research funding.
US Cancer Statistics: 1999–2011 Incidence and Mortality Web-based Report combines the data sources of Centers for Disease Control (CDC), the National Program of Cancer Registries (NPCR), and the National Cancer Institute’s (NCI’s) Surveillance, Epidemiology, and End Results (SEER) Program, producing a collaborative set of federal cancer incidence statistics (newly diagnosed cases) for a single year. Mortality statistics from the CDC’s National Vital Statistics System are also included and report 2011 cancer deaths both nationally and by state.
Analytic epidemiology: The goal of analytic cancer epidemiology is to identify the factors that predispose individuals to a cancer diagnosis and to quantify risk. Cancer risk factors include environmental exposures, genetic susceptibility, and immunosuppressive state and may be secondary to a history of malignancy, viral infection, or medical therapy. These risk factors can account for various aspects of carcinogenesis and assume varied degrees of causal primacy.
Clinical epidemiology: Epidemiologic research plays an important role in the development of cancer-screening modalities and prevention strategies. Cancer prevention focuses on decreasing incidence by lowering risk through changes in lifestyle patterns and behavior. Primary prevention attempts to stop the development of cancer. Secondary prevention aims to improve cure rates by cancer screening and early diagnosis and treatment.
Cancer screening involves testing to detect early-stage cancer in asymptomatic individuals. Ideally, screening tests should be easy to administer, noninvasive, and inexpensive. To be beneficial, early detection should alter prognosis and improve survival.
Emerging data and discovery: New data are rapidly emerging that are changing cancer screening and prevention practices. Although these changes are quite positive, the proliferation of data can create confusion among health consumers and avenues to receive reliable information are needed.
For example, the human papillomavirus (HPV), types 16 and 18, has been causally related to cervical intraepithelial neoplasia. A history of genital warts is linked to human papillomavirus types 6 and 11 and may explain the increased risk associated with multiple sexual partners. Other sexually transmitted viruses, such as herpes simplex virus 2, may interact as etiologic factors. The vaccines Gardasil and Cervarix protect against four HPV types, which together cause 70 percent of cervical cancers and 90 percent of genital warts. Ideally, girls and young women should get the vaccine before they are sexually active because the vaccine is most effective in those who have not yet acquired any of the four HPV types covered by the vaccine. Girls and women who have not been infected with any of those four HPV types will get the full benefits of the vaccine; those who are sexually active may also benefit from the vaccine, although they may get less benefit from the vaccine if they may have already acquired one or more of the HPV types covered.
One would assume that the worldwide annual rate of 266,000 deaths from cervical cancer could easily be reduced by application of the vaccine but this new technology raises questions and obstacles to care, along with offering care. The need to vaccinate women before they become sexually active raises ethical issues, particularly among populations that fear the vaccine will send a message condoning teenage sexual activity. Other issues revolve around who should advertise and promote the vaccine, how it should be promoted in developing nations, and whether parents who resist vaccination should be held liable for their children’s sexual health. These and a host of other issues demonstrate how medical advances complicate cancer epidemiology as well as offering hope.
Sociocultural issues: A sensitive issue regarding cancer screening relates to the fact that cancer prevention and control efforts center on the development of strategies to benefit the general population rather than individual lives. As new knowledge and technologies have proliferated at unprecedented rates, many ethical questions such as fair and equitable allocation of health resources across diverse populations, the priority of individual needs versus those of the social aggregate, and the unfair distribution of resources to privileged groups have come under considerable scrutiny. Some of these issues have become especially poignant as genetic technologies have identified specific ethnic factors to enhance the risk for certain cancers. The incidence increases fiftyfold in whites and thirtyfold in African Americans between the ages of fifty and eighty-five. African Americans have the highest incidence of prostate cancer in the United States, whereas American men of Asian/Pacific Islander descent have the lowest rates. African American men tend to have metastatic disease at diagnosis. The overall survival rate for African American men is 10 percent lower than that for white men, even when they are diagnosed at the same stage of disease. Endometrial carcinoma is the most common gynecologic malignancy. Its incidence is highest among white women, whereas its mortality rates are higher among African American women. Incidence rates have been declining, except among African American women over fifty years old. Cultural, psychosocial, and demographic factors may discourage the use of genetic testing services among individuals who could benefit from them or, conversely, may promote use when testing has the potential to create more harm than benefit.
To develop effective cancer detection and prevention programs, therefore, it is essential to consider cultural, demographic, and psychosocial issues that may foster or hinder utilization. Consumer lead advocacy groups have taken a grassroots approach to soliciting research dollars to fund basic and clinical research programs. That fact alone may skew inquiry toward those cultural, ethnic, and socioeconomic subgroups who value and can interpret results of medical research and who have sufficient personal resources to advocate on their own behalf. Lack of interest in genetic testing has been associated with less education, minority status, lower socioeconomic status, and less performance of other health-promoting behaviors.
Culture plays a central role in determining health beliefs, attitudes, and behavior, but few health care providers realize that health is a cultural concept defined differently across cultures. Many are unaware that the health care system is culturally designed and administered largely according to mainstream values. In genetics, cultural consideration is particularly important. Although knowledge that certain diseases run in families spans all societies, beliefs about causation of familial diseases vary considerably. Cultural attitudes toward disease also differ among ethnic populations. Moreover, culture comes into play in provider-client interaction and communication, which are both key components of genetic counseling. People from cultures that expect authority figures to be directive may find nondirective genetic counseling confusing and bewildering. Between 1970 and 1990, the minority population grew at a rate about three times that of the total population. The US Census Bureau indicates that minorities account for about 25 percent of the US population in 2014. Given these trends, attention to ethnocultural barriers is paramount in achieving universal access to genetic services.
Although cultural competency is not a licensing requirement for health professionals, it is vital in view of the sensitive nature of the issues to be discussed and the need for privacy and confidentiality of information exchanged. The professional genetics community includes few minorities, despite demographic trends further limiting the access of minorities to culturally sensitive and relevant genetic services. This lack of input from minority communities also limits the shaping of public policy and planning of genetic research and counseling in ways meaningful to ethnic minorities.
For individuals to benefit from genetic services, those services must be available, culturally appropriate, accessible, and affordable. Unless such issues are addressed, any attempt to broaden access to genetic services will be limited and perhaps even hazardous to a less informed population. Few primary care providers are ready to take on these new tasks. They need education in understanding not only the scientific advances in genetics but also their ethical, legal, cultural, and psychosocial implications.
Inadequate appropriations to develop the needed service infrastructure have resulted in an inadequate number of genetic specialists, primary care providers, and public health providers prepared to incorporate genetics into practice. Among primary care providers, inadequate preparation in genetics is compounded by the severe time constraints imposed on virtually all service providers and by a lack of reimbursement for cognitive services.
Most consumers also have low scientific literacy and know little about basic genetics or genetic testing. Without a degree of genetics literacy and an understanding of the limitations and risks involved including insurance and employment discrimination, psychological trauma, intrafamilial conflict, and social stigmatization, people cannot make truly informed decisions.
Chemoprevention: A relatively new approach to cancer prevention is through chemoprevention (as opposed to chemotherapy, or drug treatment, following a cancer diagnosis). Cancer chemoprevention is defined as the reversal of carcinogenesis in the premalignant phase. The observation that retinoids, acting as modulators of cell differentiation, are effective in suppressing oral carcinogenesis and, therefore, in preventing second primary tumors in squamous cell carcinoma of the head and neck has led to the evaluation of these agents as chemopreventive therapy for tumors of the upper aerodigestive tract in high-risk populations. Studies of adjuvant hormonal therapy with tamoxifen for breast cancer have shown a 50 percent reduction of contralateral disease, which led to a national tamoxifen chemoprevention trial to evaluate risk reduction for primary breast cancer in women at high risk. With the development of new molecular techniques, chemoprevention trials will be aided by the identification of markers for premalignant lesions.
Prognosis for cancer epidemiology: Decision making regarding genetic susceptibility testing, health surveillance, chemoprevention and preventative surgery are being quickly added to the realm of health care options without adequate knowledge among professionals and the public regarding the meaning and practical relevance of this information. Psychosocial, cultural, and economic factors may affect the study, dissemination, and utilization of genetic discoveries to create service barriers and widen the gap between the haves and have nots among health care consumers. Genetic information is received against a backdrop of deeply held personal beliefs. The influence of culture on health beliefs and actions is enormous, and the role that culture, ethnicity, and religion play in formulating an individual’s motivation toward health-seeking behaviors must be addressed in all educational and clinical activities.
American Cancer Society. “History of Cancer Epidemiology.” Cancer.org. American Cancer Society, 12 June 2014. Web. 3 Oct. 2014.
Boffetta, Paolo, Stefania Boccia, and Carlo La Vecchia. A Quick Guide to Cancer Epidemiology. New York: Springer, 2014. Digital file.
Centers for Disease Control. US Cancer Statistics: 1999–2011 Incidence and Mortality Web-Based Report. Division of Cancer Prevention and Control, National Center for Chronic Disease Prevention and Health Promotion, 2 Sept. 2014. Web. 3 Oct. 2014.
Dennis, Leslie K., and Deborah Dawson. “Meta-analysis of Measures of Sexual Activity and Prostate Cancer.” Epidemiology 13.1 (2002): 72–79. Print.
Gandini, S., H. Merzenich, C. Robertson, and P. Boyle. “Meta-analysis of Studies on Breast Cancer Risk and Diet: The Role of Fruit and Vegetable Consumption and the Intake of Associated Micronutrients.” European Journal of Cancer 36 (1990). Print.
Green, Lawrence W., and Marshall W. Kreuter. Health Promotion Planning: An Educational and Ecological Approach. 3rd ed. Mountain View: Mayfield, 1999. Print.
Harris, Randall E. Epidemiology of Chronic Disease: Global Perspectives. Burlington: Jones, 2013. Print.
Little, Jullian. Epidemiology of Childhood Cancer. Lyon: Intl. Agency for Research on Cancer, 1999.
Moolgavkar, S., et al., eds. Quantitative Estimation and Prediction of Human Cancer Risks. Lyon: Intl. Agency for Research on Cancer.
Soliman, Amr, David Schottenfeld, and Paolo Boffetta. Cancer Epidemiology: Low- and Middle-Income Countries and Special Populations. New York: Oxford UP, 2013. Digital file.
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