The continuing debate about prostate-specific antigen testing for the diagnosis of prostate cancer could be potentially resolved by the use of magnetic resonance imaging, according to the authors of a Perspective published in the Medical Journal of Australia.
Authorities in both the United States and Canada have advised physicians against prostate-specific antigen (PSA) testing because of the "overdiagnosis and overtreatment of indolent
prostate cancer".
However, Dr Jeremy Grummet and Associate Professor Richard O'Sullivan, from Epworth
Healthcare in Melbourne, wrote that in Australia, "instead of population-based screening, decisions about PSA testing of men aged 55–69 years should be shared by doctors and individual patients".
An elevated PSA level typically leads to a transrectal ultrasound-guided (TRUS) biopsy, they wrote.
"The poor specificity of PSA for significant prostate cancer is well known. What may not be such common knowledge is that about half of all TRUS biopsies are negative for cancer.
"A large proportion of the prostate cancer currently diagnosed by the combination of an elevated PSA level and a TRUS biopsy is actually low-risk disease. The vast majority of such cases require nothing more than active surveillance, but many of the men involved, unfortunately, are subjected to unnecessary treatments, although this is improving."
Grummet and O'Sullivan suggested that multiparametric magnetic resonance imaging (mpMRI) may be a diagnostic tool that can more reliably detect significant prostate cancer, while excluding indolent disease, by directing a subsequent biopsy to suspicious areas seen on mpMRI.
Two studies, one conducted in Sydney and one in Brisbane, have found that "mpMRI was
considerably more sensitive than TRUS biopsy in detecting significant cancer" — only 3% were missed by mpMRI in the Brisbane study, compared with 28% not detected by TRUS biopsy.
The overdiagnosis of low-risk cancer could also be significantly reduced by mpMRI-targeted
biopsies, and the need for biopsy by around 50%.
"These landmark reports argue in favour of a significant future role for mpMRI in the diagnosis of prostate cancer", they wrote.
Even though mpMRI is not currently reimbursed by Medicare, "it may ultimately be cost-effective".
However, mpMRI is complex imaging with a significant learning curve. For mpMRI to be of true benefit, it is therefore critical that they are ordered by the patient's treating urologist and reported by a radiologist experienced in the test. Further long-term assessment of patient outcomes werealso needed, Grummet and O'Sullivan wrote.
"The role of mpMRI in prostate cancer detection is rapidly evolving.
"By enabling targeted biopsies that exclusively detect significant cancer, mpMRI may provide the diagnostic accuracy that has been so sorely lacking.
"As such, it has the potential to revolutionise both the diagnosis and treatment of prostate cancer."