An increase in the rate of incurable prostate cancer cases could be a signal to rethink Canada’s stance on screening for one of the most common diseases among men, according to new research.
The new study, published in Current oncologyanalyzed decades of prostate cancer cases and deaths. It found that rates of late-stage cancers have increased while mortality rates, which had been declining for years, have stabilized.
“Although we could not find out who was tested, the large number of cases allows us to draw some conclusions about what happens when the test is performed or not,” said Dr. Anna W.Ilkinson, lead author and family physician at the University of Ottawa.
But some oncologists disagree with how the data has been interpreted and argue that the screening tool, known as prostate-specific antigen (PSA) testing, is inaccurate and could lead to overdiagnosis and the harms of unnecessary treatment.
Detection changes
The Canadian prevention task force has never advocated for prostate cancer screening.
But in the early 1990s, the United States approved the use of the PSA test, which Wilkinson said led to wide acceptance here as well. In the early 2010s, the United States changed and both countries aligned against screening, allowing researchers to study how case and death rates changed in the context of changing recommendations.
“What we really found is that since the recommendations against screening in the U.S.,” Wilkinson said, referring to between 2010 and 2021, “stage four or metastatic prostate cancer has increased by 50 percent in men ages 50 to 74, and by about 65 percent in men over 70.”
The study also found that mortality rates plummeted when screening received broader support and stabilized after recommendations against it.
But for 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 making, mortality rates continue to fall. “That means this probably has more to do with all the advances in prostate cancer treatment we’ve made over the last few decades.”
James Dickinson, one of the authors who recommended against PSA testing in Canada, says the data is strong but disagrees with the interpretation.
He says the increased incidence of late-stage cancer can be attributed to improvements in imaging technology, but is also a byproduct of less detection.
“If you do less screening, you’ll find less cancer,” said Dickinson, a professor of family medicine at the University of Calgary. “And more will be found when you have symptoms, so it is likely [would] be in later stages, in older men.”
Simple but controversial test
One of the key issues is the PSA test itself, a blood test that measures a protein produced by the prostate. Too much and it could be a sign of a problem.
“The test itself is not that accurate,” said Suping Ling, who researches cancer care at the London School of Hygiene and Tropical Medicine. “For a screening test, it can identify many cases of false positives.”
That inaccuracy, she and other experts maintain, will lead down a potentially more damaging path.
“There will be more people who will need follow-up to get a more accurate diagnostic test,” [such as] “MRI, biopsy, which is invasive,” Ling said. The United Kingdom 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 can lead to incontinence or sexual dysfunction. Furthermore, he says that not all cancers need to be removed, so we need a test that can be more specific.
“We need to differentiate between prostate cancer that will take your life… and prostate cancer that might just be there and grow slowly,” Gyawali said.
Wilkinson, the study’s author, agrees, but says we have made progress in minimizing harm, including the option of doing nothing.
“There has been a shift toward dissociating diagnosis and treatment,” Wilkinson said.
“Active surveillance involves following those lower-risk prostate cancers so that treatment is not harmful, but you are ready to intervene when necessary.”
burden of knowledge
Denis Farbstein, 72, knows both the benefits and risks of screening. His “adventure,” as he calls it, began with a PSA test at the age of 48, but involved testing and follow-up for six years.
“They followed me for six years, taking public service tests every 18 months, and my numbers were going up,” Farbstein recalled. They even did biopsies, one of which caused an infection. He eventually underwent surgery and has been cancer-free for nearly two decades.
“If they hadn’t examined me, it could have gone to other parts of my body and then I would have had problems. So, personally, I was very fortunate,” he said from a Toronto clinic where he volunteers, helping patients with newly diagnosed prostate cancer.
Her case is not unique, but it indicates a culture that Gyawali says has formed around screening, where the success of individual cases is used to justify decisions at the population level. He says whether screening tests find anything or not, there is relief and that intervening is justified in itself.
“There are many, many people with these benign cancers who undergo these procedures, but some end up suffering from the complications of those procedures for the rest of their lives,” Gyawali said.
“But even these people will always consider their exam to be the right thing to do.”
New guidance on all cancer screenings is expected next year, following an external review that halted the work of the responsible body, the Canadian Task Force on Preventive Health Care. While prostate cancer guidelines were due to be updated, public health officials told CBC News, the pause includes “developing guidelines, including prostate cancer screening.”
Both the Canadian Cancer Society and the Canadian Urological Association advocate PSA screening, but only after discussing the harms and benefits with your doctor.
