UROLOGY : CLINICAL UPDATES FROM THE PRACTICE
UTILIZATION OF MULTI-PARAMETRIC MRI OF THE PROSTATE IN THE TRIAGE EVALUATION OF AN ELEVATED PSA
AUTHOR Jamie C . Messer MD
The utilization of Prostate Specific Antigen ( PSA ) screening for prostate cancer remains a controversial topic since the 2012 decision by the US Preventative Service Task Force ( USPSTF ) to recommend against the routine utilization of PSA screening . 1 While prostate cancer is the most common solid organ malignancy , diagnosed in approximately 1 in 9 men , the risk of death from it is much lower than the incidence at around 1 in 37 lifetime risk of death from prostate cancer . Evidence regarding PSA screening impact on Prostate Cancer Mortality is contradictory at best , with screening leading to a small reduction in risk of death from prostate cancer . 2 , 3 The classic screening for prostate cancer would include PSA , digital rectal examination ( DRE ), and then random sampling of the prostate by Transrectal Ultrasound guided ( TRUS ) prostate needle biopsy with 12 cores . This diagnostic pathway is unfortunately very imprecise , which can lead to both over-diagnosis of clinically insignificant prostate cancer , and failure to detect clinically significant prostate cancers . This standard diagnostic pathway may lead to the over-diagnosis and potentially the over-treatment of up to 45 % of men diagnosed with prostate cancer - those who have indolent tumor biology . 3
Conversely , TRUS with standard 12 core biopsy may miss the diagnosis of clinically significant cancers in up to 30 % of patients , leading to inappropriate risk stratification and under-treatment . 2 ,
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The diagnostic lack of precision of standard TRUS with 12 core biopsy , coupled with over-treatment potentially of clinically indolent cancers was a significant factor influencing the US Preventive Services Task Force ( USPSTF ) recommendation against PSA screening . After this decision , however , there was an increase in the diagnosis of higher grade and locally advanced tumors . Thus the USPSTF softened the recommendation against PSA screening , stating instead that we screen men aged 55-69 after shared decision making with the patient regarding the risks and benefits of treatment . 1
This situation spurred many urologists and urologic oncologists to investigate modulating this diagnostic pathway to improve the diagnostic accuracy of PSA screening prior to invasive testing .
The goal is to improve the diagnostic accuracy for clinically significant cancer while avoiding the over-diagnosis / over-treatment of indolent prostate cancers . A promising addition to this diagnostic pathway is multiparametric Magnetic Resonance Imaging of the prostate ( mpMRI ). Initially introduced in the 1980s to improve staging of prostate cancer , the technology has seen a resurgence within the past decade thanks to improvement in imaging resolution and refinement and standardization of results reporting with the Prostate Imaging and Reporting Data System ( PIRADs ). 5 The PIRADs scale results in a less subjective 1-5 scoring system for MRI lesions , better correlating with the risk of significant prostate cancer . PIRADs 1 goes with very low risk , and PIRADs 5 with high risk of a clinically significant cancer . In 2014 , the PIRADs version 2 was published with a significant improvement in the algorithm and simplification of the interpretation , designed to yield greater reproducibility of this scoring system . 6 The scoring system utilizes T2 weighted imaging intensity , Diffusion Weighted Imaging ( DWI ) and dynamic contrast enhancement ( DCE ) in conjunction with size to assign a PIRADs score .
To date , mpMRI has been used mostly in men who have undergone a previous standard 12 core TRUS biopsy with a persistently elevated PSA , at risk for clinically significant cancer . This pathway evaluates high risk lesions which may have been missed on standard biopsy template ; it helps to avoid repeat biopsy if the MRI lacks high risk lesions ( typically classified as PIRADs 4 or 5 ). 7 Recently , much research has focused on choosing this technique as the initial screening examination in the biopsy naive patient . This pathway could lead to avoidance of biopsy in patients with a normal mpMRI and / or biopsy solely of lesions noted on mpMRI in those patients with a high risk mpMRI lesion . Currently , the European Association of Urology ( EAU ) and the National Comprehensive Cancer Network ( NCCN ) state that evidence is insufficient to recommend routine use of mpMRI in biopsy-naive men , although these guidelines strongly recommend using mpMRI in patients with prior negative biopsy . Ideally , the utilization of mpMRI could allow assessment of the risk of a clinically significant cancer prior to initial biopsy and therefore potentially avoid biopsy altogether in those patients with a negative mpMRI . While the evidence is conflicting with regards to this question , a recent study ( PROMIS ) reported that
6 LOUISVILLE MEDICINE