Prostate cancer is the most common cancer among men in the UK and the second most common after skin cancer in the USA – about 1 in 4 cancers diagnosed in men are prostate cancer. Prostate cancers vary enormously in terms of how aggressive they are. At one end of the spectrum are ‘hawks’ – aggressive cancers which spread to other parts of the body and account for many of the 10,000 UK and 26,000 US deaths a year. At the other end of the spectrum are ‘doves’ – slow-growing cancers that wouldn’t have caused any symptoms or spread if they hadn’t been found. The treatments for these are very different.
What was the study about and why?
Doctors have been looking at new ways of making a final diagnosis of prostate cancer in men who have a raised PSA level, and who might have prostate cancer.
They want more accurate ways of telling the difference between hawk and dove cancers, so they can treat the former quickly and decisively but avoid unnecessary overtreatment for the latter. Doctors work out the difference by a combination of the PSA level, the type of cells found in the cancer and how far it has spread.
About ¾ of men who have a raised PSA turn out not to have prostate cancer at all. PSA naturally rises with age, and a common non-cancerous condition called benign prostatic enlargement also puts it up. These are known as ‘false positive’ tests – people who have a positive result (raised PSA) but who turn out not to have the condition you’re looking for (prostate cancer). Doctors also want accurate ways of ruling out prostate cancer without patients needing invasive tests.
Catching prostate cancer before it spreads is crucial, caught early, 99% of men will still be alive five years later. If the cancer has already spread when it’s diagnosed, five-year survival drops to 28%. But treatment can cause side effects, including incontinence and erectile problems. Treating a very slow-growing cancer in an 80-year-old, who would have lived a normal lifespan in blissful ignorance if the cancer hadn’t been found, would be cruel and unnecessary.
Traditionally, many men with possible prostate cancer undergo biopsies, taken under ultrasound control through the rectum. This removes small samples of tissue that can be examined under the microscope to test for cancer. It’s not ideal – it can be difficult to find the cancerous tissue accurately using this technique; it’s an unpleasant procedure to go through; and complications include pain, infection and bleeding.
MRI scans could give a more accurate picture of how far the cancer has grown. The study was also designed to see whether some of these patients could have cancer reliably ruled out without having to go through a biopsy.
How did they do it?
This new study used multi-parametric MRI scanning – a sophisticated technique that measures not just the size and shape of the prostate but also the blood flow through it. It involved 576 UK men who underwent both MRI scanning and traditional trans-rectal ultrasound guided biopsy (TRUS-biopsy).
They also had another form of biopsy called trans-perineal prostate mapping (TPM-biopsy), with the needle inserted through the skin of the perineum, between the base of the penis and the rectum. TMP-biopsy is the ‘gold standard’ in terms of diagnosis at the moment, but is more invasive and so isn’t routine practice in the UK. All these men would have gone through the TRUS-biopsy process if they had been referred today on the NHS – the triple investigation allowed the accuracy of current and possible future tests to be directly compared.
What did the results show?
Of the 576 men in the study, 408 were diagnosed with cancer. However, almost 44% of these turned out to have a ‘clinically insignificant’ cancer.
The MRI identified that 27% of men didn’t have a clinically significant cancer – their raised PSA had been a false positive result. This means that if MRI scanning were routinely done before a biopsy, 1 in 4 men would not have needed a biopsy at all. In this study, nearly 6% of men having a biopsy had complications, including 1.4% developing sepsis. Men given the all clear through MRI scanning, who did not need to go on to have a biopsy, would obviously avoid these risks.
The MRI also picked up 93% of ‘clinically significant’ cancers – more than the TRUS-biopsy, which picked up 48%.
However, the MRI had a lower level of specificity. If a test is 80% specific, this means that 80% of the positive results it gives really are positive, while 20% are false positives who don’t actually have the disease. The specificity of the MRI was 41%, compared to a 96% specificity for TRUS-biopsy. If MRI scans were used alone, many people might progress to full treatment unnecessarily.
What does it mean for patients?
This study showed that using multi-parametric-MRI scanning as the first investigation for patients with possible prostate cancer could reduce the number of men needing biopsies by 25%. Other patients would still need a TRUS-biopsy as well, but the combination of the two could almost double the chances of picking up aggressive cancers.
The National Institute for Health and Care Excellence (NICE), are apparently looking into the possibility of changing their recommendations on the standard investigation for prostate cancer to include multi-parametric-MRI scanning.
The other cancer story this week is about how burnt toast can increase your risk of developing cancer, all due to acrylamide.
Read on to my other blog article here to find out more about this risk.
Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. Patient Platform Limited has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.