Using a selective screening strategy for prostate cancer may reduce the harms associated with prostate-specific antigen (PSA) testing while preserving the number of lives saved, according to a study by Hutchinson Center researchers.
Lead author Dr. Ruth Etzioni and Roman Gulati of the Public Health Sciences Division, along with University of Washington urologist Dr. John Gore, found that compared with a standard screening strategy, using higher thresholds for biopsy referral for older men and screening men with initially low PSA levels less frequently may be a way to improve the tradeoff between screening benefits and overdiagnosis. Their findings were published Feb. 5 in Annals of Internal Medicine.
The researchers used a computer model to compare 35 screening strategies that varied in terms of age of first and last screening, screening intervals, and PSA thresholds for biopsy referral. They looked at false-positive results, cancer detected, overdiagnoses (cancers detected that would otherwise never become clinically significant), deaths from prostate cancer, lives saved, and months of life saved.
Measuring PSA levels can help doctors determine which patients may be at risk for prostate cancer. Patients with an elevated PSA level may require a biopsy to determine if cancer is present. However, biopsies are associated with many troublesome side effects and still cannot tell a doctor with certainty which cases of prostate cancer are life-threatening and require treatment.
Controversial current guidelines
Current prostate cancer screening guidelines have been the source of controversy. Last spring, the U.S. Preventive Services Task Force concluded that the harms of existing PSA screening strategies outweigh the benefits. Other advisory groups are less clear, recommending informed decision-making on an individual level. This can be difficult because there is sparse data available to help doctors have nuanced conversations with their patients about whether and how often to have prostate cancer screening.
The researchers found that doing PSA tests less often in men at low risk of prostate cancer would substantially reduce the harm of overtreatment, while increasing the risk of death only slightly. Specifically, their evaluation showed screening men ages 50 to 74 with low PSA levels every other year instead of annually would increase the lifetime death risk by 0.1 percent, from 2.15 percent to 2.23 percent. At the same time, it would reduce number of PSA tests by 59 percent, and false positives, which often lead to painful biopsies, by almost half.
Setting a higher threshold for PSA levels for older men would accomplish the same thing. In older men, screening up to age 74, but recommending biopsies only in men with PSA levels in the top 5 percent for their age, increased the probability of lives saved more than it increased overdiagnoses.
The National Cancer Institute and Centers for Disease Control and Prevention funded the study.
[Adapted from an Annals of Internal Medicine tip sheet]