A large new study of U.S. veterans suggests that when prostate cancer screening rates go down, the number of men diagnosed with advanced cancer then rises.
Researchers found that across 128 U.S. veterans health centers, the rate of PSA screening for prostate cancer declined between 2008 and 2019 -- a period where guidelines came out recommending against routine screening.
But patterns varied among the individual centers, with some maintaining high screening rates.
And in subsequent years, the study found, a trend emerged: VA centers with higher PSA screening rates had fewer cases of metastatic prostate cancer, while more cases were diagnosed at centers with lower screening rates.
Metastatic refers to prostate cancers that have spread to distant sites in the body and cannot be cured.
Experts said the findings do not mean that all men at average risk of prostate cancer should be routinely screened for the disease.
But the results do add to a longstanding debate over the issue.
Prostate cancer is very common: About 1 in 8 men will be diagnosed with the disease in their lifetime, according to the American Cancer Society. But the cancer is often slow-growing, and may never progress to the point of threatening a man's life: About 1 in every 41 men actually die of the disease.
That's why routine screening -- with blood tests that measure a protein called PSA -- has been controversial. The main concern is that it may often detect small tumors that would never have become harmful -- leading to "over-treatment" that exposes men to the risks of side effects such as incontinence and erectile dysfunction.
Adding to that, two major trials published about a decade ago came to conflicting conclusions about the value of screening. One, done in the U.S., found that annual PSA screening did not reduce men's risk of being diagnosed with metastatic prostate cancer, or of dying from the disease.
The other trial, done in Europe, found that screening did reduce advanced cancer diagnoses.
In 2012, the U.S. Preventive Services Task Force (USPSTF) recommended against routine PSA screening for average-risk men.
Studies since then have charted an increase in metastatic prostate cancer among U.S. men. But it has not been clear whether declines in PSA screening, and missed chances to catch early cancer, are to blame.
The new findings suggest that declines in screening are part of the story, according to lead researcher Dr. Alex Bryant.
"I think it is likely that part of the recent increase in metastatic prostate cancer cases is due to historical declines in PSA screening," said Bryant, a radiation oncologist at the University of Michigan Rogel Cancer Center in Ann Arbor.
But, he added, it's "unlikely to be the full story."
According to the researchers, the magnitude of the increase in metastatic cancers does not appear to be explained by the change in PSA screening alone. It's not yet clear what the other explanations might be, Bryant said.
The findings were published Oct. 24 in JAMA Oncology and presented Tuesday at a meeting of the American Society for Radiation Oncology, in San Antonio.
The study showed that between 2005 and 2019, VA centers' PSA screening rates fell from about 47% to 37% -- meaning the proportion of men age 40 and up who'd been screened that year.
Meanwhile, metastatic prostate cancer rates rose from roughly 5 per 100,000 men in 2005, to almost 8 per 100,000 in 2019. Comparing health centers, the researchers found, those that maintained higher screening rates had fewer advanced cancer cases: For every 10% increase in the screening rate, the incidence of metastatic cancer dipped by 9%.
Experts not involved in the study were divided on whether that information is useful to individual men.
Dr. Anthony Corcoran, who directs urologic oncology at NYU Langone Hospital - Long Island, said it is.
In 2018, the USPSTF again updated its recommendations, saying that for 55- to 69-year-old men, the decision on whether to have PSA screening should be individualized -- after a discussion of the pros and cons with their doctor.
Corcoran said the new findings are another piece of evidence that screening lessens the chances of being diagnosed with metastatic cancer. But, he said, that still has to be balanced against the downsides of screening for any one man.
Age alone should not be the deciding factor, Corcoran said. A 70-year-old in good health could have many years of life ahead and benefit from PSA screening; a 70-year-old in poor health may not.
"The decision to screen should be based on a patient's overall health and what they value," Corcoran said.
Dr. Robert Dreicer, deputy director of the University of Virginia Cancer Center in Charlottesville, did not consider the findings useful for individual decision-making.
"The data here are interesting and provocative," said Dreicer, who is also an expert with the American Society of Clinical Oncology. But, he added, they only show a relationship between facility-level PSA screening rates and metastatic cancer cases -- which is not proof that screening will protect men from developing advanced cancer.
However, all three doctors agreed that those one-on-one discussions are key to making screening decisions.
Dreicer said it's important for men to understand their baseline risk of prostate cancer, since those at increased risk stand to benefit more from screening.
That group includes Black men and men with a father or brother who developed prostate cancer before age 65. The American Cancer Society recommends that they talk with their doctor about PSA screening starting at age 45. That discussion should take place sooner -- age 40 -- if a man has more than one first-degree relative who developed prostate cancer at an early age.
The American Cancer Society has more on prostate cancer screening.
SOURCES: Alex Bryant, MD, MS, radiation oncologist, University of Michigan Rogel Cancer Center, Ann Arbor; Anthony Corcoran, MD, MS, assistant professor, urology, NYU Long Island School of Medicine, director, urologic oncology, NYU Langone Hospital - Long Island, Garden City, N.Y.; Robert Dreicer, MD, deputy director, University of Virginia Cancer Center, Charlottesville, and volunteer expert, American Society of Clinical Oncology, Alexandria, Va.; JAMA Oncology, Oct. 24, 2022, online; American Society for Radiation Oncology meeting, Oct. 25, 2022, San Antonio