An initial prostate-specific antigen level of less than 3.0 ng/mL can be safely used to stratify men at low risk of developing prostate cancer, according to data from a large, European population-based study.
The overall risk of prostate cancer death in 15,758 middle-age and elderly men with a PSA level of less than 3.0 ng/mL was 0.14/1,000 life-years, which is 3.5-fold lower than the population-based risk of 0.49/1,000 life-years.
In addition, the risk of prostate cancer death within this low-risk group increased with higher baseline PSA values, senior investigator Monique J. Roobol, Ph.D., said during a Feb. 15 press briefing for the symposium on genitourinary cancers in Orlando, where the data will be formally presented.
Prostate-specific deaths increased fourfold among those with PSA levels between 1.0-1.9 ng/mL and 7.6-fold amongst those with PSAs between 2.0-2.9 ng/mL when they were compared with men who had an initial PSA below 1 ng/mL (0.17% vs. 0.35% vs. 04%, respectively). The median time from diagnosis to death was 8.3 years among men in the lowest PSA group.
The results justify using the PSA threshold of 3.0 ng/mL or more as an indication for biopsy and contribute to risk stratification and management of men in PSA-based screening programs, she said. For example, the favorable outcome in men with initial PSA values of less than 1.0 ng/mL supports prolonging the screening interval for up to 8 years.
Press briefing moderator Nicholas Vogelzang of US Oncology said men with a PSA value less than 1 ng/mL and probably those with a PSA less than 2 ng/mL could be considered for substantially longer intervals of PSA screening.
"I believe this study gives us some confidence that annual PSA screening is going to soon become a thing of the past," Dr. Vogelzang said.
The study, which is part of the larger European Randomized Study of Screening for Prostate Cancer, screened 19,950 men between ages 55 and 74 years and recommended biopsies only for those with PSA levels of 3.0 ng/mL or more. Cancers were identified at rescreens conducted every 4 years or clinically during screening intervals. The median follow-up was 11 years.
Of the 19,950 men screened, 15,758 (almost 80%) had a PSA level less than 3.0 ng/mL, observed Dr. Roobol, an epidemiologist in the department of urology at Erasmus University Medical Center in Rotterdam, the Netherlands. In all, 915 of the 15,758 men (5.5%) were diagnosed with prostate cancer, and 23 died (0.14%) from the disease.
Men with a PSA level of less than 1.0 ng/mL were 2.7-fold less likely than were those with a PSA of 1.0-1.9 ng/mL to develop aggressive prostate cancer, and 6.2-fold less likely to do so than were their counterparts with a PSA of 2.0-2.9 ng/mL.
When asked whether patient age at the time of the initial PSA affects the findings, Dr. Roobol acknowledged that the age range in the study was not very broad but said that the PSA range is much more predictive than age.
Fellow presenter Dr. Neil Fleshner, head of urology at the University Health Network in Toronto pointed out that growing evidence suggests that the PSA test is better in younger men than in older patients where there is confounding with benign prosthetic hyperplasia. He also noted that the entire screening process will be refined with the emergence of new biomarkers in the coming decade.
Dr. Roobol responded that the PSA is very valuable in identifying men at low risk of prostate cancer and can remove almost half of men aged 55 to 74 years from the need for continued testing. Once that’s done, clinicians can use better biomarkers to increase detection in the remaining half.
"I think PSA is a very good first step," she said.
Dr. Meelan Bul, lead author, who is also from Erasmus University Medical Center, will present the study at the symposium, sponsored by the American Society for Clinical Oncology, the American Society for Radiation Oncology and the Society of Urologic Oncology.
Dr. Roobol disclosed a consultant/advisory role with Bechman Coulter, GlaxoSmithKline and Gen-Probe. Coauthor Dr. Fritz H. Schroder also disclosed consulting/advising for GSK. Dr. Vogelzang disclosed relationships with multiple pharmaceutical companies.