What is the PLCOTrial?
If you are reading this first issue of the national PLCO newsletter, you are considering or have already decided to participate in one of the most important health studies in the United States&emdash;the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial. The information gathered from the 148,000 volunteers like you will influence the health care of Americans over age 54 for generations to come.
The National Cancer Institute (NCI), the Federal Government's primary agency for cancer research, is sponsoring the PLCO Trial to find out if screening tests will reduce the number of deaths from prostate, lung, Colorectal and Ovarian cancers. The men and women who volunteer for this trial are asked to fill out health questionnaires once a year for up to 14 years. By chance selection some volunteers are assigned to receive cancer screening tests at no cost during the initial visit and once every year for the next 3 years. While taking part in PLCO, participants will also have the opportunity to take part in other related scientific studies to examine whether diet and the environment are factors in the development of cancer.
A screening test is an examination performed on healthy people by a health professional. It may find cancer before the cancer causes symptoms, though most people screened will not have cancer. Doctors and scientists know that for a few types of cancers, early detection can improve life expectancy. For example, the Pap smear can detect precancerous cervical cells in women. Cervical cancer can be prevented when these cells are removed. But, for many other kinds of cancer, including the widespread cancers of the prostate, lung, colon and rectum, and ovaries, doctors don't know whether benefits of some screening tests outweigh potential harms.
Different screening tests are being studied in PLCO for each of the four cancers. The specific tests are:
By the end of the PLCO study about ten years from now, researchers expect to understand the benefits and limitations of each test. They expect to learn if using these tests to detect cancers early and treating them appropriately extend lives that might otherwise be lost to prostate, lung, colorectal, or ovarian cancers.
Why two study groups?
To discover the answers to these questions, the PLCO study has been designed in a special way called a "randomized controlled trial" or RCT. This type of clinical trial is the best method of evaluating the effects of medical practices such as screening. In an RCT, half the volunteers are assigned by chance to a group who comes in for screening tests (called the intervention group). The other half are assigned by chance to a group that does not receive any particular screening or treatment other than their usual source of care (called the control group). Both groups are vital to learning the answers and advancing medical care. Volunteers have a 50-50 chance of being assigned to either group. This technique, called randomization, helps avoid biasing or having the study's results inadvertently affected by factors not related to the screening test being studied.
Over the years of PLCO, researchers will compare the health of the two groups. They will see whether the number of deaths from these four types of cancer were the same or different in each group. For participants whose results from a screening test indicate they might have cancer, researchers will examine if and how follow-up diagnostic tests can affect people. For those participants who do develop cancer, researchers will examine the side effects of treating cancers. By examining each of these factors, PLCO researchers will be able to determine if the cancer screening tests had an overall benefit.
You should be proud of your contribution in helping to advance the fight against cancer. Whether you are randomized to the screening or usual care group, your participation is a vital part of the PLCO study. Both groups of participants&emdash;the screening and usual care groups&emdash;are critically needed to determine the answers to cancer screening and prevention questions.
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