Volume 2, Number 1 ----- Spring/Summer 1999
NCI is as anxious as participants are to learn the important results of the PLCO trial. Unfortunately, NCI will not have final screening results from the PLCO trial for many years. Good science cannot be rushed. Clinical trials take time to design, conduct, and analyze. The PLCO trial is a particularly lengthy trial for three reasons:
It is a prospective early detection trial.
These trials enroll healthy individuals and monitor their health as they age. PLCO will not be finished until NCI follows participants' health over the course of 13 or more years, although some scientific results will emerge sooner.
Its statistical power is high.
Scientists rely on "statistical power" to ensure that any effect reported from the final data analysis is not due to chance. To have sufficient statistical power, scientists need a large group of participants. The number of participants in a trial is called the "sample size." It takes time to recruit a large sample size. More than 120,000 men and women are enrolled in PLCO. Another 28,000 participants are yet to be enrolled. Each of the 148,000 participants must be followed for at least 13 years.
It will generate enormous amounts of data.
It takes a lot of time to ensure that all of these data are correctly reported and properly analyzed.
By following this careful research design, NCI ensures that when the results are analyzed and announced, PLCO participants and the medical community will be able to trust the results. As the years progress and as results are produced, we will be sure to share them with you.