After a recommendation against routine prostate cancer screening, rates of early disease declined while the incidence of advanced disease rose. The trend highlights the difficult balance between screening and potential overtreatment.
The rate of advanced prostate cancer in men aged 50 or older continued to rise between 2005 and 2016, even as the frequency of early stage prostate cancers dropped, according to a study published in the Journal of the National Cancer Institute.
The study’s authors suggest that the redistribution of diagnoses may be associated with recommendations against routine screening for the disease made by the U.S. Preventive Services Task Force (USPSTF) in 2008 and 2012.
In fact, previous studies found that the U.S. incidence of local-stage prostate cancer
dropped while the incidence of regional- and distant-stage disease increased soon after the
USPSTF made its recommendations against routine screening, Dr. Ahmedin Jemal and fellow researchers at the American Cancer Society (ACS) noted. Their study looked at whether these patterns persisted in the longer term, through 2016.
In 2008, the USPSTF recommended against prostate-specific antigen (PSA) testing in men aged 75 and older, and in 2012, the panel of experts recommended against the screening in all men. In 2018, the USPTF recommended individual decision-making about screening for men aged 55 to 69 and said that men 70 and older should not be screened.
PSA is a protein produced by cells in the prostate gland, but if the level of the protein reaches abnormally high levels in the blood, it could signal that prostate cancer is present. PSA testing is controversial because it is not a guaranteed way to detect prostate cancer.
Levels of the protein can rise for reasons other than prostate cancer, leading to unnecessary biopsies that can cause pain, bleeding or infection and raise anxiety for patients. And while a re-analysis of two large clinical trials showed a 25% to 30% relative reduction in the risk of prostate cancer death with screening versus no screening, the testing can lead to the identification and treatment of slow-growing prostate cancers that, if never found, would not be harmful.
In fact, in those two trials and one other, 16.4% to 50.4% of prostate cancers were overdiagnosed, the USPSTF noted in its 2018 recommendation. This is problematic, the organization noted, because treatment for prostate cancer can leave patients with long- term side effects, including incontinence and erectile dysfunction.
The USPSTF’s recommendations have been controversial, with some experts believing the guidelines have led to a larger proportion of prostate cancers being diagnosed at later stages, when they pose a greater threat to patients’ lives and may require more aggressive treatment.
According to the ACS, the rate of routine PSA testing has dropped since the USPSTF recommended against it.
A national survey of men aged 50 and older showed that their past-year routine PSA testing rates declined from 40.6% in 2008 to 38.3% in 2010 and 31.5% in 2013, remaining unchanged in 2015, an ACS press release stated.
In the recent study, the team led by Jemal, a cancer epidemiologist who heads the Surveillance and Health Services Research Program at the ACS and is an adjunct professor at Emory University in Atlanta, used data from the U.S. Cancer Statistics Public Use Research Databases to analyze how much the rate of invasive prostate cancer changed each year from 2005 to 2016 in men aged
50 and older. Within the study, the men were divided into groups based on disease stage (local, regional or distant), age (50 to 74 versus 75 or older) and race/ ethnicity (all races and ethnicities, non-Hispanic Whites and non-Hispanic Blacks).
The researchers found that, across patients of all participating races and ethnicities, the incidence of local disease dropped by 6.4% per year from 2007 to 2016 in men aged 50 to 74. In men aged 75 and older, the incidence of local disease declined by 10.7% annually from 2007 to 2013 and then stabilized from 2013 through 2016.
In contrast, the incidence for prostate cancer that had spread to distant parts of the body rose in both age groups during the study period. For example, distant- stage incidence in men aged 75 and older increased by 5.2% per year from 2010 to 2016.
“These data illustrate the trade-off between higher screening rates and more early stage disease diagnoses (possibly overdiagnosis and overtreatment) and lower screening rates and more late-stage (possibly fatal) disease,” the authors wrote. “Several modeling studies, however, showed that the harms associated with higher PSA screening rates can be mitigated while preserving the benefit of screening.”
That could be done by waiting longer between screenings, raising the PSA level associated with the need for biopsy in older men and restricting routine testing to men younger than age 70, the authors suggested.
Additionally, the study identified a substantial decline in racial disparity in the incidence of distant-stage disease, largely confined to men aged 50 to 74 years, which coin- cided with a steeper increase in distant-stage incidence in non-Hispanic White men. Nevertheless, incidence rates in non-Hispanic Black men remained two to three times as high as in non-Hispanic White men.
“Reasons for this disparity are not fully understood, but in part are thought to reflect differences in lifestyle factors, biological susceptibility and access to care,” the authors wrote. “Obesity and cigarette smoking are more prevalent in (non-Hispanic Black) than (non-Hispanic White) men.
Furthermore, the association of obesity with prostate cancer risk is stronger in (non-Hispanic Black) men.”
Across the whole study population, the researchers suggested that family history and cigarette smoking were unlikely to be responsible for the changes in prostate cancer incidence. However, they said that the importance of an increase in excess body weight since the 1970s deserves study.
Their analysis did not cover the period after 2018, when USPSTF recommendations changed again; the impact of that change on prostate cancer rates has not yet been measured, according to the ACS.
“Regional- and distant-stage prostate cancer incidence continue to increase in the U.S. in men aged 50 years or older, and future studies are needed to identify reasons for the rising trends,” the authors concluded.
Jemal said that all men aged 50 and older with a life expectancy of at least 10 years should receive information about the potential benefits, risks and uncertainties of prostate cancer screening in order to make informed decisions with their health care providers about whether to undergo testing.