Volume 2, Number 1 ----- Spring/Summer 1999
Amy Subar, who has a Ph.D. in nutrition, is responsible for designing surveys and other tools to study how diet might affect a person's risk for cancer. Her most recent project has been a survey called the "Diet History Questionnaire," which all PLCO participants are being asked to complete.
This confidential and anonymous survey will help researchers see what links exist between what people eat and cancer incidence. It took three years to develop.
"Results from this survey will form a rich bank of information to determine whether and how diet affects cancer risk," said Dr. Subar. Right now, PLCO scientists are focusing on how antioxidants, fiber, and fruits and vegetables might decrease risk of cancers. Scientists are also looking at how fat intake might increase risk for some cancers. "However," Dr. Subar explained, "as research advances and ideas evolve about nutrition and cancer prevention, we will be able to use the database of information provided in the Diet History Questionnaire to generate and explore new theories."
Dr. Subar is particularly interested in the role of fruits and vegetables and diet as a total package. "I don't think the answer will be one magic bullet vitamin or mineral," said Dr. Subar. "There are countless complex interactions among compounds in one food, let alone among foods in a person's total diet. That is why we need to eat a variety of foods in our daily diets. I doubt we will ever isolate a single food, vitamin, or nutrient as a 'cure'."
The survey is a long list of questions, but most participants are able to finish it in about one hour. Participants don't have to finish the survey all at once. "If you want to take a break and come back to the survey another day, that's okay," Dr. Subar advised. "But please be sure to fill out all of the questions on all of the pages." If surveys are only half finished, they will not be accurate and NCI will not be able to use them.
"Thank you very much for your time and honesty. We know it takes a long time to answer all of the questions, but your answers are critical to our understanding of how diet works to prevent cancer," Dr. Subar concluded.
Richard Hayes, Ph.D., is the NCI Principal Investigator responsible for creating and maintaining ways to collect biologic samples and information about participants' lifestyles. He then coordinates scientific studies using this material.
In addition to studying the effectiveness of screening tests, PLCO is also studying how people's lifestyles and biologic makeup, including genetics, interact to develop cancer and other diseases. When they fill out surveys--like the Diet History Questionnaire, participants give lifestyle information such as how much they exercise, what foods they eat, and if they smoke. Screening arm participants can also choose to give a sample of their blood for biologic studies. These samples are stored in a special lab called the "PLCO Biorepository."
Usual care participants will soon have a chance to contribute to these studies. Beginning in October of this year, usual care participants will receive in the mail an envelope with a buccal cell collection kit. Buccal cells (pronounced "buckle") line the inside of the mouth and, like all cells in the body, contain the genetic backbone, DNA.
"Collecting buccal cells is a very simple and painless task that should only take a few minutes in your home," Dr. Hayes said describing the test process. To give a sample:
Participants are free to choose whether or not they want to give samples for these studies. Participation in these studies is completely voluntary. Your samples will be kept confidential. Your name will not be attached to your sample.
If you don't see your kit right away, don't be surprised. There are so many participants in this trial, it may take up to three years to mail out the kits to all usual care participants.
"We have an incredibly powerful opportunity with the PLCO Biorespository to study risk factors for cancer," said Dr. Hayes. "This is research work," he explained, "so we cannot make results available for individual participants."
Participants may be curious to know what types of studies will be conducted. As Dr. Hayes explained, "We believe that biologic factors, including genetics, may determine how the body handles certain chemicals and that the knowledge gained from these studies will point to ways to prevent cancer and other diseases."
Dr. Hayes wishes to thank all of the participants who continue to support the PLCO trial with their time and commitment.