Moving into the final recruitment phase, the researchers of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO) are seeking 75,000 more men and women ages 55 to 74 to help them determine whether medical tests to detect some of the most common cancers reduce the number of deaths from these diseases. This largest-ever US cancer screening trial will include a total of 148,000 men and women in 10 cities: Denver, Colorado; Washington, DC; Honolulu, Hawaii; Detroit, Michigan; Minneapolis, Minnesota; St Louis, Missouri; Brooklyn, New York; Pittsburgh, Pennsylvania; Salt Lake City, Utah; and Marshfield, Wisconsin.
Together, prostate, lung, colorectal, and ovarian cancers account for nearly half of all cancers diagnosed and half of all cancer deaths in the United States. Late in 1995, the age range for PLCO trial participants was expanded from ages 60 to 74 to ages 55 to 74. "Almost 80% of cancers occur in people who are age 55 and older," said John Gohagan, phd, Chief of NCI's Early Detection Branch and project officer for the study. "By lowering the age for participation, we are including more people who are already at risk." The investigation began in November 1993.
The tests being studied may detect these cancers before symptoms develop, but whether treatments at this stage will reduce the chance of dying from the diseases is unknown. Some cancer screening tests very clearly reduce the number of deaths from the disease-for example, Pap tests reduce deaths from cervical cancer. But many other medical tests are being routinely used to screen healthy people for cancer when there is no definitive evidence that they reduce the number of deaths from the disease.
PLCO trial participants are being randomized to one of two groups: Half the participants undergo the tests being studied (intervention group), and half receive whatever usual health care their doctors provide (control group). Both groups will answer yearly questionnaires about their health.
Tests Under Study
"Whether the participants receive their usual care from their physicians or receive cancer screening tests at the PLCO centers, they are playing an important role," Dr. Gohagan said. By comparing the numbers of cancers diagnosed, side effects of treating the cancers, and the numbers of cancer deaths in the intervention group with those in the control group, the researchers will be able to determine if the cancer screening tests had an overall benefit. The following tests are being studied:
- For prostate cancer, men have a digital rectal examination of the prostate and a blood test for prostate-specific antigen.
- For lung cancer, both men and women receive a regular chest x-ray.
- For colorectal cancer, men and women are screened with flexible sigmoidoscopy.
- For ovarian cancer, women have a physical examination of the ovaries, a blood test for the tumor marker CA125, and a transvaginal ultrasound.
The intervention group has these tests done at their initial visit and during the third year of participation. Participants in both the intervention and control groups are contacted yearly for at least 10 years from the time they enter the study in order for the researchers to monitor their health.
Men and women interested in participating in the PLCO trial should contact the center nearest them. Locations of the centers can be found by calling NCI's Cancer Information Service at 1-800-4-CANCER (1-800-422-6237). Information about the PLCO trial can also be found on the World Wide Web at http://www.dcpc.nci.nih.gov/PLCO.