The American Cancer Society’s cancer prevention studies help researchers identify cancer risk factors by allowing them to study large groups of people over long periods of time.
The American Cancer Society first began conducting long-term prospective studies (also called follow-up studies) in the 1950s. For these studies, large groups of individuals were recruited through a successful partnership between American Cancer Society researchers and volunteers. The study populations provide information (e.g. lifestyle, medical, or behavioral) at the time of enrollment and then are followed over time to assess their health outcomes. The commitment of the study participants and the volunteers who recruited them has been vital to the success of these studies.
The Hammond-Horn cohort study, conducted from 1952-55, was the first cancer prevention study that the American Cancer Society conducted. It provided the first U.S prospective evidence confirming the association between cigarette smoking and lung cancer, cardiovascular disease and other conditions in men. This cohort included 188,000 men recruited by 22,000 volunteers.
The success of this early cohort led the Society to invest in a series of large prospective cohort studies to identify the causes of cancer: Cancer Prevention Study I (CPS-I, 1959-72), CPS-II (1982-present), sub-cohorts of CPS-II, and the newest cohort CPS-3 (2006-present).
Contributions of the Cancer Prevention Studies
The Cancer Prevention Studies have provided unique contributions both within the American Cancer Society and in the global scientific community. These contributions allow the Society to focus its resources on factors most important in preventing cancer and promoting health.
American Cancer Society epidemiologists have published more than 750 scientific articles from these studies, the findings of which have significantly contributed to tobacco-related research, and to the understanding of obesity, diet, physical activity, hormone use, air pollution, and various other exposures in relation to cancer and other diseases.
Key findings from these studies include:
- The link between smoking and lung cancer: Early American Cancer Society epidemiologic studies provided some of the strongest evidence linking smoking with lung cancer and higher overall death rates. This evidence led to the Surgeon General’s landmark 1964 conclusion that smoking causes lung cancer, helping drive a decline in adult smoking rates from over 40% in 1964 to less than 20% today. American Cancer Society epidemiologic studies continue to document the ongoing health impact of smoking. In 2014, the Surgeon General used our results to show that over 480,000 Americans die each year from smoking cigarettes.
- The risks of obesity: CPS-I provided the first epidemiologic evidence that obesity increases risk of premature death, and subsequent studies from CPS-II helped to establish the link between obesity and death from breast, colorectal and other cancers.
- The possible role of aspirin in cancer prevention: In the early 1990’s, CPS-II was the first prospective study to find a link between regular aspirin use and lower risk of colorectal cancer, a finding confirmed by many later studies. These results opened the door to ongoing studies in the U.S. and internationally to find out if aspirin might lower risk of other cancers and to better understand the overall risks and benefits of aspirin use.
- The evidence basis for the Society’s Guidelines on Nutrition and Physical Activity for Cancer Prevention: Our studies showing that high red and processed meat and alcohol intake, low physical activity and longer sitting time increase risk of cancer or mortality have contributed to the scientific evidence based for the development of the Society’s Guidelines on Nutrition and Physical Activity for Cancer Prevention. Moreover, findings from CPS-II were used to demonstrate the lifesaving potential of a lifestyle consistent with our guidelines.
- The connection between air pollution and mortality: Findings from CPS-II contributed substantially to the scientific evidence associating increasing levels of specific types of air pollution with higher deaths rates from cardiovascular disease and lung cancer. These studies are cited prominently by both the Environmental Protection Agency and World Health Organization in policies and recommendations for U.S. and world-wide air pollution limits.
- The identification of important genetic mutations associated with certain cancers: CPS-II data and biospecimens have been included in the identification or validation of nearly every confirmed breast, prostate and pancreatic cancer genetic variant known to date. This work has led to a better understanding of family history of these cancers. The long-term aim of this research is to identify men and women at particularly high risk of the disease who may benefit most from enhanced screening, lifestyle modifications and/or chemoprevention.
Future Directions of the Cancer Prevention Studies
American Cancer Society researchers continue to study the CPS-II cohort and, in the future, will begin to study the new CPS-3 cohort to learn even more about cancer risks.
Future research avenues include:
- Cancer risk factors among those aged 65 and older: Given the increasing number of adults aged 65 years and older in the U.S. – this population is expected to go from 40.2 million in 2010 to a projected 88.5 million by 2050 – we will leverage the large size, long-term follow-up and older age of CPS-II participants to study factors associated specifically with cancer risk and with longevity in the elderly.
- Predictors of early onset cancer: The large number of younger women and men in CPS-3 will allow us to study predictors of early onset cancers, such as premenopausal breast cancer.
- Further study of second-hand smoke and e-cigarettes: We will investigate the effects of second hand smoke exposure during childhood on adult cancer risk. In addition, we are beginning new research to determine how e-cigarette use may influence the smoking of regular cigarettes.
- Additional investigation into obesity: With nearly 28% of US adults being obese, we will study the evolving role of diet, physical activity, aging and the built environment on changes in overweight and obesity to better inform cancer prevention programs. In addition, given the increasing number of adults who have lived with obesity throughout adolescence and young adulthood, we will examine long-term obesity in relation to cancer incidence and survival.
- Risk factors for specific molecular subtypes: Collection of tumor tissue specimens will allow us to identify risk factors for specific molecular subtypes of colorectal, prostate, hematologic, ovarian, and breast cancers (for example estrogen receptor positive breast cancer), leading to development of better targets for prevention.
- Cancer survivorship: With over 14 million cancer survivors alive today in the US and an estimated 19 million by 2024, we will utilize the information collected from CPS study participants both before and after a cancer diagnosis to study factors associated with cancer survivorship and to inform cancer survivorship guidelines.
- The relationship between lifestyle and genetics in cancer risk: Utilizing the biospecimens collected from our CPS-II and CPS-3 participants, we will study the interplay between lifestyle and genetic factors in relation to cancer risk and survival.