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
percent of cancers occur in people who are age 55 and older," said John Gohagan, Ph.D., 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 study got under way in
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, such as Pap tests
which 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 randomized (selected by chance) 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.
"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," said Gohagan. 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 tests being studied are:
For prostate cancer, men have a digital rectal exam of the prostate and a blood test for prostate-specific antigen, known as PSA.
For lung cancer, both men and women receive a regular chest x-ray.
For colorectal cancer, men and women are screened with a lighted instrument called a flexible sigmoidoscope that lets health professionals see the inside of the rectum and the lower part of the colon.
For ovarian cancer, women have a physical exam of the ovaries, a blood test for the tumor marker known as CA125, and a test called transvaginal ultrasound.
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 (Internet) at: http://www.dcpc.nci.nih.gov/PLCO.
The Cancer Information Service provides a nationwide telephone service for cancer patients and
their families, the public, and health care professionals. The toll-free number is
1-800-4-CANCER (1-800-422-6237); services provided in English and Spanish. People with
TTY equipment may call 1-800-332-8615.
This document is available through the NCI's CancerNet services on the Web
(http://cancernet.nci.nih.gov) and through Cancer Fax (dial 301-402-5874 from the handset on
your fax machine).