By Alpa Patel, PhD
How often do you see someone battling cancer and wish there was something tangible you could do to make a difference?
During the past 50 years, more than 2 million volunteer participants have joined the American Cancer Society's Cancer Prevention Studies and have been making a difference simply by giving a little time to fill out surveys and share information about their behaviors, lifestyle, family and personal medical history, and other information. In 1959 and 1982, adult men and women voluntarily joined the Cancer Prevention Studies I, and II, respectively. Their simple actions as study participants have helped us understand much of what we know about how cancer develops in the population.
Today, a new generation can do the same, by joining the Cancer Prevention Study-3 (CPS-3), the Society's newest Cancer Prevention Study.
Teasing out lifestyle risks
So, how can simply providing information about how you live help researchers understand the causes of cancer and how to prevent it?
Studies like CPS-3 enroll large numbers of adults who have never been diagnosed with cancer. These individuals provide information about themselves at the start of the study. Researchers "follow" study participants over time by periodically sending follow-up surveys that ask about changes in lifestyle or behaviors, and about any new health outcomes (like cancer).
Over time, some individuals in the study population will develop cancer and some won't. Using the information provided, researchers compare the people who developed cancer with those who didn't and examine whether specific "exposures" result in a higher or lower risk of developing cancer. For example, a recent study from CPS-II showed that men and women who consumed 3 or more drinks of hard liquor a day were more likely to die of pancreatic cancer compared to those who did not consume alcoholic beverages.
These types of studies are called "epidemiologic cohort studies" and we have learned a lot from them:
- They uncovered the link between smoking and higher risk of lung cancer.
- They found the association between being overweight or obese and more than 10 different types of cancer.
- They showed that physical activity is associated with lower risk of various types of cancer, including breast and colon cancer;
- They uncovered the association between post-menopausal hormone use and higher risk of breast cancer.
The findings from these studies are not just scientific- they also provide the evidence we rely on to help shape health advice for the public, develop nutrition and physical activity guidelines and cancer prevention programs, and contribute to our advocacy efforts to change policies. Think about how difficult it would be to pass a smoke-free law without any scientific evidence that second-hand smoke is harmful!
Without epidemiologic studies, the only way to understand how different factors affect cancer risk would be to conduct a controlled experiment. In a controlled experiment, half of the population would be told to do something -- say, smoke a pack of cigarettes daily -- and the other half would not smoke. Researchers would then examine how smoking affects different health outcomes. Clearly though, it would not be ethical or practical to conduct a controlled experiment on smoking.
In epidemiologic cohort studies, researchers can collect information on what people are already doing in their daily lives, without asking them to change their behaviors. We can simply observe them, and then study the associations with different health outcomes, like cancer.
Paying it forward
CPS-3 is not only collecting information through surveys; when they sign up, participants will also have their waist circumference measured and provide a small blood sample as well. This added information lets the researchers improve their understanding of how genes and lifestyle "interact" to trigger cancer development. Using all of this information together, researchers can examine the interplay between genetic predisposition, lifestyle, behaviors, environment, and different factors in the blood (like proteins, hormones, nutrients, and more), in relation to cancer risk.
In CPS-3, we are also working to recruit a more diverse study population than those in the past. Minority populations have not been well-represented in epidemiologic cohort studies, but CPS-3 aims to include at least 25% non-white participants. The President's Cancer Panel, in a report published in Spring 2011, concluded "The current understanding of cancer risk, progression, and outcomes is based largely on studies of non-Hispanic white populations. The risk factors, screening guidelines, and treatment regimens identified through research are often not appropriate for individuals of non-European descent."
While we have made tremendous progress in the fight against cancer, studies like CPS-3 are essential to help us continue to improve our understanding of how cancer develops in a population. Simple actions truly have the potential to change the face of cancer. Just think about the monumental progress made since the first Cancer Prevention Study was established in 1959 in getting cancer under control. For just one example, as noted above, CPS-I uncovered the link between smoking and lung cancer. At that time, approximately half of American men smoked cigarettes. The findings from these studies have been monumental in providing the scientific evidence that has resulted in changing society's views of smoking, smoke-free legislation, and as a consequence, lower smoking rates.
Each generation of study participants in these American Cancer Society studies paid it forward to help us understand what we know today. With all of the changes in the way we live today compared to the population in CPS-I (recruited in 1959) or CPS-II (recruited in 1982 and on average over 80 years old today), to continue to improve our understanding of cancer for the next generation, we too must pay it forward.
For more information about the Cancer Prevention Studies or to learn more about signing up to be a participant in CPS-3, please visit www.cancer.org/preventcancer.
Dr. Patel is strategic director of the Cancer Prevention Study-3 for the American Cancer Society.