New statistics from the Australian Government show that prostate cancer continues to be the most commonly diagnosed cancer for Australian men. But a recent publication has predicted that 41% of prostate cancer diagnoses in Australia have been unnecessary. Over-diagnosis due to PSA-testing has been a controversial issue for many years. This week’s blog reports on prostate cancer diagnosis and overdiagnosis rates in Australia.
Prostate cancer diagnosis rates in Australia
New figures from the Australian Institute of Health and Welfare (AIHW) predicted that prostate cancer continues to be the most commonly diagnosed cancer in Australian men. But these figures do not include non-melanoma skin cancer, which is higher. The new data come from a recent report called Cancer in Australia 2019. We expect an estimated 19,508 men to be diagnosed in 2019 through prostate biopsies. This number doesn’t include men who have a high PSA or positive MRI, but who refuse a biopsy. The AIHW also predicts that over 3,300 men will die from prostate cancer this year.
The good news is that the 5-year survival rate is now at an estimated 95.2%. For men diagnosed with stage 1, 2 or 3 prostate cancer, these rates are close to 100%. So nearly all of men diagnosed at these early stages remain alive 5 years after their diagnosis.
The latest report in Cancer in Australia 2019 as also tells us:
- In the 2-year period 2015-2016, there were 1,355,803 men who received a Medicare-subsidised PSA test.
- Prostate cancer was the most common cancer in men for which radiotherapy was used. 25.8% of radiotherapy services in men were for treatment of prostate cancer.
- In the 2011-2015 period, prostate cancer had the 3rd highest 5-year survival rate amongst cancers in men. Leading prostate cancer were testicular cancer and thyroid cancer.
Prostate cancer diagnosis rates in Australia have varied considerably over the past 30 years. Soon after PSA testing for men without symptoms was subsidised by Medicare, diagnosis rates rose rapidly. These peaked in 1994 (dark blue line on the graph below). A rapid fall after this time is not surprising, as many men with high PSA levels had already been diagnosed in the past couple of years. A second peak occurred in 2009. We don't really undestand why diagnosis rates were so high at this time. There were probably many different factors affecting this second peak.
Despite the rapidly changing patterns in diagnoses, the mortality rate from prostate cancer (light blue line on the graph below) has been dropping consistently since the early 1990s. This has probably been due to a number of different factors, such as early detection from PSA-testing and new and improved treatments.
Overdiagnosis of prostate cancer in Australia
In the years following the uptake of PSA-testing, it’s been recognised that prostate cancer has been over-diagnosed and over-treated. This refers to diagnosing and treating prostate cancer in men for which that cancer was not going to kill them or even lead to symptoms.
Why is this happening? The PSA test can detect prostate cancer that is very slow growing. Men with very low-risk prostate cancer have a very low chance of dying from this disease, even if they receive no treatment at all. Diagnosis of very low risk prostate cancer is considered harmful. It leads to enormous distress and pressure on these men and their families. Before active surveillance became popular, the majority of these men had treatment. They then suffered the side effects of treatment, such as urinary and bowel incontinence, infertility and problems having sex. We now know that these very low-risk prostate cancers would not have led to death, and many not even have led to any symptoms, in the vast majority of these men. So the damaging treatment they had did not help them.
The harms of treatment, for the majority of these men with very low risk disease, did not outweigh the benefits. This is called over-treatment.
We have known for quite some time that we are diagnosing and treating some men with prostate cancer who were very unlikely to die, and even unlikely to ever have symptoms from this disease. This is exactly why PSA testing is so controversial.
PSA-testing does, however save lives. PSA testing also detects the higher risk cases of prostate cancer that need treatment. But it does so at a cost of over-diagnosis and over-treatment for some men.
A recent scientific publication has predicted that, from the years 1982-2012, 41% of Australian men diagnosed with prostate cancer were “over-diagnosed”. Over-diagnosis was defined, in this study, as diagnosing a man with prostate cancer when that cancer was not going to lead to any symptoms. Therefore, the diagnosis, and any treatment, were unnecessary and potentially harmful.
41% may sound surprisingly high. But their results are similar to other international studies.
It’s likely that this over-diagnosis rate won’t be so high going into the future. This analysis ended in 2012. Since that time, diagnosis rates have dropped. PCFA’s PSA-testing guidelines, released in 2016, are helping to ensure that PSA-testing is used by the men who will benefit from it, reducing over-diagnosis. PCFA recommends that men between the ages of 50 and 69 should talk to their doctor about the pros and cons of PSA-testing. If they choose testing, a test every 2 years is recommended. If PSA is over 3 ng/ml, then this should be followed-up. But for a man with a family history of prostate cancer, testing should start before 50 years of age.
It’s also worth noting that over-diagnosis does not necessarily mean over-treatment. In the past, up until about the year 2000, most men diagnosed with low-risk prostate cancer were treated. Now active surveillance is very common. About 70% of men with low-risk prostate cancer now choose active surveillance. This means that they delay their treatment until it becomes necessary, if it does so. By reducing over-treatment, the harms of over-diagnosis are being reduced.
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