Prostate Cancer Diagnoses Fall as Use of PSA Test Declines

Pam Harrison

May 23, 2017

Rates of prostate cancer in the United States dropped by 53% from 1992, when prostate-specific antigen (PSA) testing was widely used, to 2013, the latest year for which data are available. The finding is highlighted in a commentary in JAMA Oncology published online May 11, which asks whether this is good or bad news.

It's a bit of both, the editorialist write. "The decline in cancer incidence in elderly men is probably mostly good news.... In contrast, the decline in prostate cancer diagnosis among younger men is ominous."

"It's not that there is less cancer — there's the same amount of cancer — it's just being diagnosed less," editorialist Meir Stampfer, MD, DrPH, Brigham and Women's Hospital and Harvard Medical School in Boston, Massachusetts, told Medscape Medical News.

"The reason why this is more ominous in younger men than in old men is because prostate cancer has a very long natural history, so a large proportion of old men, even if they have a potentially aggressive cancer, will likely die of something else because of their advanced age.

"But in young men, we are missing out on an opportunity to prevent prostate cancer deaths by failing to detect them early, and the fact that incidence rates of prostate cancer have gone down means that detection has declined but the cancer's still there."

No Cause for Celebration

"Normally, we would celebrate a decline in cancer incidence rates," the editorialists write.

"But for prostate cancer, changing rates largely reflect screening practices and do not reflect the enormous prevalence of undetected prostate cancer," they add — an estimated 42 million US men today have undetected prostate cancer. Fewer than 3 million have been diagnosed with prostate cancer.

"The major concern, of course, is whether the decline in mortality will stop or even reverse as the impact of decreased screening takes effect," they write.

SEER Analysis

In addition to Dr Stampfer, the authors are Mary Downer, Brigham and Women's Hospital and Harvard Medical School in Boston, Massachusetts, and Matthew Cooperberg, MD, MPH, Helen Diller Family Comprehensive Cancer Center, San Francisco, California.

For their article, the team conducted an analysis of Surveillance, Epidemiology and End Results Program (SEER) data. They determined that in 2013, the age-adjusted diagnostic rate was 112 prostate cancer diagnoses per 100,000 men.

This is the lowest incidence rate since 1984, before PSA screening entered the arena, the editorialists point out.

The fact that the incidence of prostate cancer in 2013 was less than half the rate it was some 20 years ago can be explained by two factors, the authors write.

"First, after more than 3 decades of widespread PSA screening to detect prostate cancer, there are few men with high PSA levels that haven't already been diagnosed," they write.

More importantly, PSA screening is less frequent now. The US Preventive Services Task Force initially recommended against PSA screening in older men, then in 2012, they recommended against screening for men of any age.

"Screening then declined in all age groups," the experts note.

However, evidence shows that mortality from prostate cancer is lower when men are screened for it. In one study cited by the editorialists, investigators reported that mortality from prostate cancer was almost 50% lower at 14 years of follow-up in men who underwent PSA testing every 2 years compared to men who did not undergo PSA testing.

"Further evidence for the national impact of PSA screening can be found in the marked decline in US prostate cancer mortality rates," the editorialists continue.

After peaking at 39 deaths per 100,000 men in 1993, mortality from prostate cancer had dropped substantially by 2013.

During that interval, the number of men who were found to have distant or advanced disease at diagnosis also declined, as they note.

Estimates suggest that an increase in PSA testing during those intervening years was responsible for about 80% of the decline in diagnoses of distant or advanced-stage disease.

A reduction in the number of men with distant or advanced disease at diagnosis does not necessarily mean lower mortality rates from prostate cancer, the editorialists point out, and they cite "disquieting" signs.

"For men younger than 65 years, mortality has stopped declining altogether, staying at 1.66 deaths per 100,000 men from 2010 to 2013," they explain.

Moreover, researchers are beginning to report that incidence rates of metastatic disease at diagnosis have recently increased in men older than 75 years, whereas rates of local and regional disease at diagnosis are down sharply.

Others have reported an increase in the incidence of metastatic disease in men with prostate cancer from 2011 to 2013.

"Because repeated PSA screening provides an average lead time of perhaps 11 years, we will likely see an increase in distant stage disease owing to decreased screening in younger age groups in a few years," the editorialists predict.

Adds Dr Stampfer: "The PSA test is a simple blood test. It provides information that is reliable, but it doesn't automatically trigger an inexorable set of steps leading to surgery or radiation," he said.

"So by not having the PSA test, basically you are throwing away the potential for information, which always seems like a bad idea," he added.

None of the authors have disclosed any relevant financial relationships.

JAMA Oncol. Published online May 11, 2017. Abstract

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