Munich, Germany (UroToday.com) Dr. Thoeny gave an overview of the role of pre-biopsy MRI for screening and diagnosis of prostate cancer and highlights that there is a clear role for pre-biopsy MRI. Currently, TRUS systemic biopsy is considered the gold standard in the diagnosis of prostate cancer. However, systemic TRUS is associated with various complications including hemorrhage and prostatitis, which may hamper image interpretation of mpMRI if it is done subsequent to a biopsy. Only 25% of men who undergo prostate biopsy with PSA 3-10ng/ml have prostate cancer and most have clinically insignificant prostate cancer.
Therefore, 75% of men undergo an unnecessary biopsy. Dr. Thoeny highlights that the problem with current methodology with systemic TRUS biopsy is a significant over-diagnosis of clinically insignificant cancer and under-diagnosis of clinically significant prostate cancer. She states that we need a diagnostic tool to detect significant prostate cancer and multiparametric MRI (mpMRI) serves that role.
Dr. Thoeny then highlights several recent studies on multiparametric MRI. Introduction of MR/TRUS fusion biopsies resulted in a higher detection rate of clinically significant prostate cancer compared to the higher detection rate of insignificant prostate cancer by random TRUS biopsy (Siddiqui et al, JAMA 2015). Targeted biopsies resulted in 30% more high-risk cancers and 17% fewer low-risk cancers than standard biopsies (Siddiqui et al, JAMA 2015). In one study, cancer positivity rate for significant prostate cancer is 40% on targeted biopsy versus 20% on systemic biopsy (Grenabo et al, Eur Urol 2016). Additionally, risk of finding significant prostate cancer increases with increasing PIRADS score (PIRADS 3 = 23%, PIRADS 4 = 75%, PIRADS 5 = 100%). Negative predictive value of mpMRI is 63-98% depending on patient selection. However, many of the recent studies indicate a NPV of up to 95% for detection of high-grade disease. Dr. Thoeny presented a study with 830 men with elevated PSA who had negative mpMRI and subsequently underwent a biopsy. The biopsy resulted in 121 patients with prostate cancer. Of which, 18 were high-grade but 15 of these were all organ confined. This resulted in NPV of 95% (Visschere et al, Eur Radiology).
Dr. Thoeny summarizes that that published data clearly suggests a role of MRI based prostate cancer screening for patients with elevated PSA. However the question is how do we make mpMRI and MRI/TRUS fusion biopsies economically feasible in a health care system. She proposes that we can investigate the minimum number of MRI sequences to get an optimized detection of clinically significant prostate cancer (T2W and DWI but no contrast medium and no endorectal coil). In her institutional study, this resulted in a sensitivity of 89-91 % and specificity of 77-81% (Bains LJ, J Urol, 2014).
While the costs of mpMRI may still be high despite limiting the sequences, it will lead to increase detection rate of significant prostate cancer. Additionally, it may allow us to forego a biopsy in up to 75% of patients with elevated PSA, which may make screening for prostate cancer more affordable. Strong collaboration between radiologists and urologists is the prerequisite for optimal patient management.
Presented By:
H. Thoeny, Berne (CH)
Reported By:
Mohammed Haseebuddin, MD, at the 31st Annual EAU Congress - March 12 - 15, 2016 – Munich, Germany
Fox Chase Cancer Center