Reductions in screening for prostate cancer using prostate-specific antigen (PSA) testing have been associated with recent increases in the diagnosis of metastatic prostate cancer. The findings add weight to recommendations that men discuss PSA screening benefits and harms with their doctor.
PSA screening was found to reduce prostate cancer metastasis and mortality in a large, European, randomized trial, but screening resulted in overdiagnosis and overtreatment of prostate cancer with significant quality-of-life implications. The U.S. Preventive Services Task Force (USPSTF) had insufficient evidence to recommend PSA screening in 2008 and recommended against screening in 2012. Subsequent analyses found that metastatic prostate cancer at diagnoses were rising in the United States.
"Although it is implied that reductions in PSA screening are responsible for the rise in metastases, this has not been directly studied. We used longitudinal statewide variations in PSA screening to test the hypothesis," said lead author Vidit Sharma, MD, health services fellow in urologic oncology at the University of California, Los Angeles, at the 2021 ASCO Genitourinary Cancers Symposium (Abstract 228).
About the Study
Researchers obtained age-adjusted incidences of metastatic prostate cancer at diagnosis per 100,000 men from the North American Association of Central Cancer Registries from 2002 to 2016 for each U.S. state. They also obtained PSA screening estimates for each state from the Behavioral Risk Factor Surveillance System. The system collects this information for men at least 40 years of age every 2 years starting in 2002. PSA screening and metastasis data were collated as a multi-panel time series and then analyzed using a random-effects linear regression model with random effects at the state level.
Key Findings
In the United States, the average percentage of men age 40 or older screened for prostate cancer using PSA decreased from 61.8 percent in 2008 to 50.5 percent in 2016. At the same time, the average number of men diagnosed with metastatic prostate cancer after adjusting for age increased from 6.4 to 9 per 100,000 men.
There was significant variation between states in terms of the percentage of men over 40 years of age who reported ever receiving PSA screening (40.1-70.3%) and in the incidence of metastatic prostate cancer at diagnosis after adjusting for age (range 3.3-14.3 per 100,000 men). A random-effects linear regression model demonstrated that longitudinal reductions across states in PSA screening were associated with increased metastatic prostate cancer. States with larger reductions in PSA screening tended to have larger increases in metastatic prostate cancer diagnoses. Variation in PSA screening explained 27 percent of the longitudinal variation in metastatic prostate cancer within states.
"The variation between states is one of the precise strengths of our study. The magnitude of decreased PSA screening was correlated to the magnitude of increased metastatic disease, suggesting that there may be a link at the population level," said Sharma.
The USPSTF updated screening guidelines in 2018 to recommend that "men aged 55 to 69 years make an individual decision about whether to be screened after a conversation with their clinician about the potential benefits and harms." The task force recommended against PSA screening in men over 70.
In conclusion, Sharma said: "Our study strengthens the epidemiologic evidence that reductions in PSA screening are likely responsible for some of the recent increase in metastatic prostate cancer at diagnosis in the United States. The trend of rising metastatic disease at diagnosis is a worrisome consequence that needs attention. To reduce the incidence of metastatic prostate cancer in the United States, we support shared decision-making policies for PSA screening, such as the 2018 USPSTF update."
The researchers plan to look for correlation between decreased screening and mortality, as well as investigating the effects of other factors.
ASCO expert Robert Dreicer, MD, MS, Deputy Director of the UVA Cancer Center, commented: "This study suggests that reduced PSA screening may come at the cost of more men presenting with metastatic prostate cancer. Patients should discuss the risks and benefits associated with PSA screening with their doctor to identify the best approach for them."
Mark L. Fuerst is a contributing writer.