A new study published Tuesday in the journal Prostate Cancer and Prostatic Disease finds a sharp increase in the number of advanced and metastatic prostate cancer cases detected annually since 2004. But the study’s other findings also reveal a complicated picture surrounding the necessity of prostate cancer screening.

Chicago researchers analyzed nine years’ worth of prostate cancer diagnoses taken from the National Cancer Data Base, spanning 2004 to 2013. They found a pattern that has continued since 2007 onwards: The number of diagnosed cases where the cancer spread beyond the prostate, or became metastatic, has risen. The annual incidence of these more life-threatening cases rose 72 percent during the study period, from 1,685 cases in 2004 to 2,890 in 2013, and the largest relative increase was seen among men aged 55 to 69.

Altogether, there was 767,550 men diagnosed with prostate cancer throughout the study’s length, with 3 percent of cases being metastatic.

“Beginning in 2007, the incidence of metastatic prostate cancer has increased especially among men in the age group thought most likely to benefit from definitive treatment for prostate cancer,” the authors wrote.

An Unneeded Test?

In 2008, the U.S. Preventive Services Task Force (USPSTF) issued a far-reaching recommendation regarding one of the most popular forms of prostate cancer screening, a prostate specific antigen (PSA) test. They advised that men over the age of 75 no longer receive the test, which measures the level of a substance released from the prostate that’s oftentimes higher in men who have prostate cancer. In 2012, the agency went even further, recommending that no men with an average risk of prostate cancer get tested for PSA.

They did so because evidence indicates that PSA tests are more trouble than they’re worth for most men. Strange as it seems, the majority of prostate cancer cases progress slowly, if at all, are very rare before age 50, and even when untreated, are rarely fatal. While prostate cancer remains among the most commonly diagnosed cancers, with 180,000 cases estimated to be found in 2016, the actual lifetime risk of a man dying from it is only 2.7 percent. Indeed, most prostate cancer patients, especially if older, will die from a myriad of other causes long before the cancer becomes an issue.

Positive PSA tests are effectively a double-edged sword for many men then, leading to invasive surgeries and exhaustive chemotherapy sessions for a medical condition that may never become serious. When it comes to false positives, which happen fairly often, a patient’s treatment ordeal would be completely unnecessary. These treatments, while relatively safe, can carry a variety of very inconvenient side effects like incontinence. There’s also no strong evidence that the other major form of screening, digital rectal exams, does much to reduce deaths from prostate cancer compared to no screening either.

The current study’s findings don’t contradict the consensus on screening, though they possibly add some nuance. For one, the annual increase in advanced cases actually began before any of the USPSTF’s new recommendations were issued, meaning that the trend can’t be completely explained by them. Secondly, the annual incidence in prostate cancer cases overall hasn’t significantly changed since 2004, indicating that while fewer men are getting screened, doctors are still catching plenty of cancers. Meanwhile, there was a sharp reduction in the number of so-called low-risk cases from 2007 to 2013, suggesting that the recommendations did help to prevent people from getting unnecessarily diagnosed.

In the wake of the study’s release, there have also been severe criticisms made by prominent cancer experts concerning how the study was conducted. And even whether the reported rise is real.

“The way epidemiologists measure things like incidence and mortality is to study rates, the number of cases per a number of people (usually per 100,000) to look for trends,” explained Dr. Otis W. Brawley, Chief Medical Officer of the American Cancer Society, in a statement released Tuesday. “But this study, done by a group of urologists, didn’t do that. Rather than measure rates of metastatic disease, they looked at the number of cases. That is far from the same thing.”

The authors, while expressing their belief that prostate cancer screening can save lives in following interviews, did note this limitation in their paper, as well as admitting that the increase in advanced cases began before 2008.

People in the study who were diagnosed with metastatic prostate cancer in 2013 had higher PSA levels than did those in 2004, indicating a greater degree of disease at the time of their diagnosis (metastatic prostate cancers are largely incurable, though again, some patients die of unrelated causes first). That trend as well as the possible increase in advanced cases could have several explanations according to senior author Dr. Edward Schaeffer, chair of urology at Northwestern University’s Feinberg School of Medicine.

"One hypothesis is the disease has become more aggressive, regardless of the change in screening," said Schaeffer in a statement. "The other idea is since screening guidelines have become more lax, when men do get diagnosed, it's at a more advanced stage of disease. Probably both are true. We don't know for sure but this is the focus of our current work."

Brawley, however, put forth yet another explanation in an interview with The New York Times: Doctors may have simply gotten better at detecting advanced cases, thanks to improvements in magnetic resonance imaging scanning.

And though Schaeffer and his colleagues believe their findings suggest that current prostate screening guidelines need to be refined, Brawley was emphatic that this study doesn’t come anywhere close to supporting such a change. “The issue of whether and how screening may affect deaths from prostate cancer in the U.S. is an incredibly important one,” he said. “[But] this study and its promotion get us no closer to the answer, and in fact cloud the waters.”

All this aside, should the average man with no history of prostate cancer in his family between the ages of 55 to 69 get screened for it? That’s a decision that should be left to the man himself and his doctor, obviously, but the evidence still suggests that the vast majority won’t benefit from it.

Source: Weiner D, Matulewicz R, Eggener S, et al. Increasing incidence of metastatic prostate cancer in the United States (2004–2013). Prostate Cancer and Prostatic Disease. 2016.

Update/Correction: This article originally detailed several criticisms of the study’s overall findings and made clear the current scientific consensus on the health benefits and risks of prostate cancer screening, but it has since been amended to include statements from Dr. Brawley of the American Cancer Society. Additionally, it has been corrected to note the study was released Tuesday, July 19, not Wednesday, July 20.