Preventing Overdiagnosis of Prostate Cancer with Improved Diagnostic Accuracy

by Dato’ Setia Dr Tan Hui Meng, Consultant Urologist, Subang Jaya Medical Centre (SJMC)

Prostate cancer is the third most common cancer among the male population in Malaysia after colorectal and lung cancer. However, despite these staggering numbers, compared to breast cancer, prostate cancer screening appears to be a very controversial topic in medicine.

To date most health professionals and the public at large are still lost and uncertain on how to go about preventive measures and the treatment of prostate cancer. Sometimes, early prostate cancers are localised and contained within the prostate. The cancer grows very slowly and may not cause problems for years or may not even become advanced cancer. In cases like these, patients do not need to be treated.

In the United States, the Preventive Services Taskforce (USPSTF) gave a Grade C recommendation on screening for prostate cancer, which means individuals do not necessarily need to screen for prostate cancer unless they have concerns and should discuss their concerns with their physicians. This recommendation came about as to reduce the overdiagnosis and overtreatment of prostate cancers.

This decision, however, has resulted in an increasing trend of prostate cancer mortality and morbidity, causing much suffering and compromising the quality of life for patients. The challenge today is to come up with a strategy to screen the right population and find lethal prostate cancers. Equally important, we will also need new treatments which are less invasive and cause less morbidity to individuals.

Improved accuracy with mpMRI screening

For more than 30 years, the medical profession did not make headway with regards to the diagnosis and management of prostate other than developing robotic techniques and better radiotherapy to remove the tumours. The diagnosis using systematic non-targeted transrectal ultrasound scan (TRUS) guided biopsy is highly inaccurate as it has high false negative rate. This is dangerous as it misses at least 50% of cancer.

The transformative advancement in the diagnosis and treatment of prostate cancer was the development of multiparametric MRI (mpMRI) of the prostate. Using mpMRI as a triage can spare significant number of men from undergoing unnecessary prostatic biopsies and avoiding both the physical and psychological trauma and morbidity especially if TRUS biopsies are performed.

Many studies have confirmed that mpMRI is highly reliable in identifying more than 90% of men with clinically significant and lethal prostate cancer. This method was reported to be much more sensitive (93%) in detecting prostate cancers compared to TRUS biopsies (48%). MpMRI as a triage also detects much fewer clinically unimportant prostate cancer (54% fewer) compared to using the traditional TRUS biopsy.

In other words, mpMRI reduces overdiagnosis of clinically unimportant cancer prostate and improves detection of clinically significant and deadly prostate cancer.

To screen or not to screen for prostate cancer?

Many screening studies have shown that men diagnosed with prostate cancers whether they are treated or not, their survival outcome is generally over 10 year or so. This shows that a majority of the men with prostate cancer detected by screening do not benefit from treatment. Instead, they suffer the consequence of treatment like losing potency, and experiencing urinary or rectal symptoms with occasional incontinence.

However, long term studies show the benefits of screening are observed after consistent follow ups for 12 years or more. The Goteborg Randomised Cancer Prostate Screening Trial done in Sweden revealed that for men who have undergone over 14 years of follow up and completed the screening, there was a 66% decrease in advanced prostate cancer in the screened population compared to the population of men who were randomised to non-screening arm.

Therefore, one can conclude that men who have serial PSA screening and then treated if prostate cancer is detected, they have a 66% less chance of developing advanced prostate cancer--which often results in very painful bone metastases. There was also a 56% lower mortality rate in the screened population. Extrapolating from this result, in the Swedish population, PSA screening can save 5,700 out of 1 million screened men from dying of prostate cancer.

The best way forward for prostate cancer screening & treatment

In summary, prostate cancer is still a significant life-threatening disease.

Early detection and early prediction of the disease is crucial, whereas screening in men with long life expectancies is beneficial. Overdiagnosis and overtreatment issues can be addressed with targeted screening and biopsy only for at-risk patients. This aims for early detection & diagnosis of localised lethal prostate cancer, which is fully curable.

If diagnosed with non-lethal prostate cancer (especially low-grade cancer), individuals only require good active surveillance with a follow-up mpMRI. They should also repeat biopsy of the prostate if necessary. It is crucial for those with intermediate grade prostate cancer (ISUP 2) or large volume low grade prostate cancer (> 6mm core cancer tissue) to receive careful active surveillance paired with good clinical judgement and a follow up mpMRI as well.

Men with localised lethal prostate cancer will need ablative treatment with surgery, radiotherapy or occasionally brachytherapy. Counselling for adverse events like erectile dysfunction and occasional urinary incontinence following ablative treatments should also be given.

MpMRI has greatly improved the diagnosis of clinically important prostate cancer and better genomics will help predict prognosis of the disease. Transperineal mpMRI – ultrasound fusion prostatic biopsy is the way forward. Focal therapy like HIFU, Irreversible Electrophoresis or targeted ablation will probably play an increasing role especially for patients with favourable intermediate risk or low grade large volume prostate cancer.

The future is definitely clearer with both the medical community and public being more confident in this era of advanced diagnostic and treatment of prostate cancer covering the whole spectrum of the disease.

Source: New Straits Times