Oxford American handbook of oncology. Second Edition. Oxford University Press (2015)
Most cancer patients are diagnosed in late stage, and even those cancers that are diagnosed at an early clinical stage are the manifestation of a much longer preclinical carcinogenic process. These observations have prompted efforts to prevent cancers, particularly in those at highest risk.
- The World Health Organization (WHO ) estimates that approximately one-third of all cancers are preventable through currently available strategies.
Overall cancer mortality rates have begun to decline in the United States, with an accelerated rate of decline observed in most recent years. This trend is thought to be due in part to more widespread adoption of primary and secondary (early detection) cancer prevention strategies.
The field of cancer prevention brings together the following disciplines:
- Experimental therapeutics
- Molecular biology
- Infectious diseases
- Public health
Approaches to cancer prevention include avoidance of chemical and physical carcinogens, excision of preinvasive lesions, prevention and eradication of cancer-associated infectious diseases, removal of organs at high risk for cancer, and chemoprevention.
Chemoprevention is the use of chemical agents or dietary compounds to reduce the incidence of cancer.
The chemical compounds could be trace elements, hormones, molecularly targeted agents, or other compounds; the dietary compounds could be fiber, nutrients, vitamins, or extracts of foodstuffs. A thorough understanding of the causes and mechanisms of carcinogenesis is the best guide to the designing of effective prevention strategies.
However, incomplete information for causation of a particular cancer type is the norm, thus the rationale for prevention strategies has often been based on epidemiological associations.
- For example, colorectal cancer is almost unknown in numerous tribes in Africa, possibly due to their high-fiber diet.
- Similarly, several studies have associated breast cancer with obesity and numerous studies have subsequently attempted to explore the relationship of fat in the diet and the onset of breast cancer.
Prevention strategies have appropriately been directed to individuals at highest risk for the target cancer.
Most current risk assessments are based on traditional clinical characteristics such as age, known exposure to carcinogens (e.g., tobacco), and presence of associated disease (e.g., ulcerative colitis).
Although some preventive approaches are now being applied more broadly to populations, such as vaccination against human papilloma virus, there is increasing emphasis on focusing prevention through use of genetic risk and more sophisticated biomarkers of cancer risk based on genomics and proteonomics. Having understood the cancer process and defined the population at greatest risk, it is easier to implement prevention approaches that are ultimately proven to decrease cancer incidence.