Vidit Sharma, MD, University of California, Los Angeles, Department of Urology, discusses a study exploring whether reductions in PSA screening are responsible for increased incidence of metastatic prostate cancer in the United States.
The results of this study were presented at the virtual 2021 ASCO Genitourinary Cancers Symposium.
I’m Vidit Sharma, and I’m a health services research fellow in urologic oncology at UCLA. My study’s titled “Reductions in PSA Screening Across States are Associated with an Increase in Metastatic Prostate Cancer in the United States.”
Just some background. PSA screening was found to reduce prostate cancer metastasis and mortality in a large European randomized trial, but PSA screening is also known to cause significant harms in terms of overdiagnosis and overtreatment for low‑risk prostate cancer.
As a result, the United States Preventive Services Task Force found insufficient evidence to recommend PSA screening in 2008 and later recommended against PSA screening in 2012. Several studies have found that there has been a rise in metastatic prostate cancer at diagnosis since that change. Several studies have also found that there’s been a decline in PSA screening since that change.
The implication, when you put both of these studies together, is that the decreases in PSA screening were responsible for the rise in metastasis, but the 2 magnitudes have not been directly linked in the United States.
Our objective was to conduct an epidemiologic study to test this hypothesis by examining statewide variation in PSA screening and statewide variation in the incidence of metastatic prostate cancer at diagnosis from 2002 to 2016.
For our methods, we extracted 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 state.
Survey‑weighted PSA screening estimates were then extracted from another dataset called the Behavioral Risk Factor Surveillance System. This collected data on PSA screening for all men at least 40 years of age every 2 years from 2002 onwards.
The PSA screening and the metastatic prostate cancer diagnosis data was then analyzed as a multi‑panel time series by state, using a random effects linear regression model, with random effects at the state level.
Basically, we found that after 2010, there was a significant decrease in PSA screening across states, and after 2010, there was a significant increase in the incidence of metastatic disease at diagnosis across states.
Regardless of the time we looked, there was significant variation between states in both of these measures. We then performed our regression analysis and correlative analyses that demonstrated that larger declines in PSA screening were correlated to larger increases in metastatic prostate cancer.
The R2 of our regression model was 0.27, indicating that the variation in PSA screening explained about 27% of the variation in metastatic disease at diagnosis. Given that our study is correlative data, there are other factors at play, as indicated, that our regression model doesn’t explain all of the variation, but there’s several other factors that could have explained some of this.
We’re working on other analyses to address this in our upcoming manuscript, but we do conclude that our study strengthens the epidemiologic evidence that reduction in PSA screening may be responsible for at least some of the increase in metastatic prostate cancer diagnosis.
We thus support policies that promote shared decision‑making to optimize PSA screening, such as the updated 2018 USPSTF guidelines, which now recommend shared decision‑making. Ideally, we hope that perhaps we may be able to optimize PSA screening, so that we can still have the benefits of lower overdiagnosis and overtreatment, but perhaps not lead to the rise in metastatic disease at diagnosis.
Thank you very much.