A surge in the rate of incurable prostate cancer cases could be a sign to rethink Canada’s stance on screening for one of the most common diseases for men, according to new research.
The new study, published in Current Oncology, looked at decades of prostate cancer cases and deaths. It found rates of late-stage cancers have gone up while mortality rates — which had been dropping for years — have levelled off.
“Although we couldn’t tell who was screened, the sheer number of cases allows us to draw some conclusions about what happens when you screen or don’t screen,” said Dr. Anna Wilkinson, lead author and family physician with the University of Ottawa.
But some cancer doctors disagree with how the data has been interpreted and maintain that the screening tool — known as a prostate-specific antigen (PSA) test — isn’t accurate and could lead to overdiagnosis and the harms of unnecessary treatment.
Shifts in screening
The Canadian task force in charge of prevention has never advocated for prostate cancer screening.
But in the early 1990s, the U.S. approved the use of the PSA test, which Wilkinson says led to a big uptake here, too. In the early 2010s, the U.S. shifted and both countries were aligned against screening, which allowed researchers to study how case and death rates changed against the backdrops of shifting recommendations.
“What we actually found is that since recommendations against screening in the U.S.,” Wilkinson said, referring to between 2010 and 2021, “metastatic or stage four prostate cancer has gone up by 50 per cent in men aged 50 to 74, and by about 65 per cent in men in their late 70s.”
The study also found that mortality rates plunged when screening was more widely supported, and plateaued following the recommendations against it.
But to Bishal Gyawali, an oncologist and associate professor at Queen’s University in Kingston, Ont., that’s a continuing sign of progress.
“No matter what [screening] recommendation you are doing, the mortality rates keep falling. So that means this has probably more to do with all the advances in treating prostate cancer that we have achieved over the last few decades.”
James Dickinson, one of the authors who recommended against the PSA test in Canada, says the data is sound but disagrees with the interpretation.
He says the higher incidences of late-stage cancer can be attributed to improvements in imaging technology — but also is a byproduct of less screening.
“If less screening occurs, then less cancer will be found,” said Dickinson, who teaches family medicine at the University of Calgary. “And more will be found when it presents with symptoms, so likely [would] be at later stages, in older men.”
Simple yet controversial test
One of the key issues is the PSA screening itself, a blood test which measures a protein that a prostate makes. Too much, and it can be a sign of a problem.
“The test itself is not so accurate,” said Suping Ling, who researches cancer care at the London School of Hygiene and Tropical Medicine. “For a screening test, it may identify lots of false positive cases.”
That inaccuracy, she and other experts argue, will lead down a potentially more harmful path.
“There will be more people who need to get followup to get a more accurate diagnostic test, [such as] MRI, biopsy, which is invasive,” Ling said. The U.K. used some of this reasoning in its draft recommendation against prostate cancer screening.
Gyawali agrees, saying the harms of acting on PSA results are real and not often talked about — including surgeries that may lead to incontinence or sexual dysfunction. Furthermore, he says not all cancers have to be removed, so we need a test that can be more specific.
“We need to differentiate between prostate cancer that’s going to take your life … versus prostate cancer that might just be there and grow slowly,” Gyawali said.
Wilkinson, the study author, agrees but says that we have made progress in minimizing the harms, including the choice to do nothing.
“There’s been a shift to decouple diagnosis and treatment,” Wilkinson said.
“Active surveillance is following those lower-risk prostate cancers so you don’t have harms of treatment, but you’re ready to jump in when you need to.”
Burden of knowing
Denis Farbstein, 72, knows both the benefits and risks of screening. His “adventure,” as he calls it, started with a PSA test at the age of 48 — but involved testing and monitoring for six years.
“I was followed for six years, having PSAs about every 18 months and my numbers would elevate,” Farbstein recalled. He even had biopsies, one of which gave him an infection. He eventually had surgery and has been cancer-free for nearly two decades.
“Had I not been screened, it could have gone into other parts of my body, and then I would have been in trouble. So, for me, personally, I was very fortunate,” he said from a Toronto clinic where he volunteers, helping newly diagnosed prostate cancer patients.
His case isn’t unique, but indicative of a culture that, Gyawali says, has formed around screening — where the success of individual cases are used to justify population-level decisions. He says whether screening finds something or not, there is relief and that taking intervention is self-justifying.
“There are so many people who have these benign cancers who undergo these procedures, but some of them end up suffering the complications of those procedures for the rest of their life,” said Gyawali.
“But even these people will always look back upon their screening as something that was the right thing that they have done.”
New guidance on all cancer screening is expected next year, following an external review that paused the work of the body in charge, the Canadian Task Force on Preventive Health Care. While prostate cancer guidelines were due for an update, public health officials tell CBC News, the pause includes “guidelines under development, including screening for prostate cancer.”
Both the Canadian Cancer Society and Canadian Urological Association advocate for PSA screening, but only after discussing the harms and benefits with your doctor.
