Initial results from an ongoing study evaluating prostate cancer screening practices demonstrate that the combined use of both standard tests — the prostate-specific antigen (PSA) blood test and the digital rectal exam (DRE) — is optimal for detecting cancer.
The results also confirm that the massive, nationwide study is well-designed to show whether current screening practices reduce death from prostate cancer.
The researchers presented their analyses of the study in two papers, one in the March 16 issue of the Journal of the National Cancer Institute and the other in the March issue of the Journal of Urology.
Begun in 1993 and continuing until 2019, the study is part of the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening trial being conducted by researchers at the School of Medicine and several other institutions to assess the effectiveness of cancer screens.
“We don’t know for certain whether prostate cancer screening saves lives,” said Gerald L. Andriole Jr., M.D., head of the Division of Urologic Surgery. “The PLCO study follows about 75,000 men — half screened by PLCO and half getting conventional care.
“By comparing the groups over the long term, we’ll be able to determine what difference screening makes in survival rates.”
Uncertainty about the need for prostate cancer screens stems from several factors. PSA and DRE tests can be inaccurate, giving both false negatives and false positives.
In addition, neither test indicates how aggressive the cancer is. Furthermore, because prostate cancers grow slowly in many cases and treatments can have unpleasant side effects, treating the disease may be less desirable than leaving it alone, especially in older men.
The PLCO study has screened 34,244 men, ages 55-74, for prostate cancer and followed their subsequent medical history.
About 14 percent of the men had positive screening results, indicative of possible cancer.
Approximately 8 percent screened positive by PSA test, and about 7 percent screened positive by DRE test.
Only about 1 percent of these results overlapped, demonstrating the importance of using both screening methods.
“We were hopeful some years ago that men could just have the PSA blood test because men hate the rectal exam,” Andriole said. “We’ve found that if you omit the DRE, you’ll miss a certain percentage of cancers.”
Men were advised to consult their own physicians for treatment if either of the tests performed by PLCO was suggestive of cancerous growth.
Three-fourths of the men with positive PLCO screens followed up with their personal physicians.
These physicians decided whether to perform a biopsy, which is needed to confirm the presence of cancer.
The initial data indicate that younger men, men with a family history of prostate cancer and African-American men are more likely to have a biopsy after an abnormal screening result.
“The biopsy statistics parallel many medical recommendations and reassure us that good judgment is being applied to the evaluation of the initial screen by physicians,” Andriole said. “So we are confident that when the study is ultimately completed, it will truly measure the effect of current medical practices.”
Overall, 1.4 percent of the men screened were subsequently diagnosed with prostate cancer by tissue biopsy.
The majority of men with prostate cancer had localized cancers. About 10 percent had more serious advanced forms. These advanced cancers were linked to higher PSA numbers and suspicious DRE results.
“We don’t know for certain whether prostate cancer screening saves lives. By comparing the groups over the long term, we’ll be able to determine what difference screening makes in survival rates.”