Active surveillance is a viable and preferred option for patients with low risk prostate cancer. However, the strategies to follow patients have been largely defined arbitrarily, since there is still a lack of high level evidence to support specific methods for surveillance such as schedule, role of biomarkers, optimal biopsy scheme, and triggers for further diagnostic procedures or interventions. Currently, the most accepted trigger for intervention is presence of higher-grade cancer (i.e. Gleason ≥ 7) in subsequent biopsy.
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It is well known that a significant proportion of patients initially classified as “low risk” actually harbor higher-grade tumors that go undetected with the traditional risk stratification methods like systematic biopsy. We designed a study to evaluate the efficacy of MRI and MRI-targeted biopsies to detect higher-grade prostate cancer in a cohort of patients with Gleason grade 3+3 prostate cancer.
We aimed to determine: (1) The negative and positive predictive values of an MRI Likert score to rule out or predict presence of Gleason score ≥ 7 in the combined biopsy strategy of systematic and MR-targeted biopsy, and (2) the relative values of MR- targeted and systematic biopsies in this population.
In this study all patients underwent a multiparametric MRI and a subsequent biopsy. A systematic biopsy was performed in all patients, and consisted of 14 cores obtained using trans-rectal ultrasound guidance. An MRI-targeted biopsy was performed in all patients with regions-of interest on MRI (i.e. MRI score ≥ 3), and included two biopsy cores obtained using visual registration (cognitive biopsy) and two cores obtained using software registration (MR-targeted biopsy). We used a computer-assisted elastic image fusion system with real-time 3D tracking technology.
Our cohort was composed by 206 patients with a previous diagnosis of Gleason grade 3+3 prostate, who were managed with active surveillance. Men with a previous diagnosis of Gleason score ≥ 7 prostate cancer, and those who had received any kind of treatment for prostate cancer were not included. The majority of patients had 2 or more positive cores with cancer, and median PSA density was 0.13 ng/ml2. Regions-of-interest suspicious for cancer were detected on MRI in two thirds of this cohort and defined by a Likert score of 3 or greater.
We found that the MRI Likert score was significantly associated with the probability of finding Gleason score ≥ 7 prostate cancer in the subsequent systematic and MRI-targeted biopsy. Patients with no suspicious areas on MRI had a low, but not negligible probability of harboring Gleason score ≥ 7 prostate cancer (11%). In patients with regions-of-interest on MRI, the degree of suspicion (represented by the MRI score) was associated with an increasing probability of detecting Gleason grade ≥ 7 prostate cancer. Specifically, patients with a region-of-interest defined by a MRI Likert score of 3, 4 and 5 were found to harbor Gleason score ≥ 7 prostate cancer in 28%, 46%, and 100% cases, respectively.
Overall, Gleason score ≥ 7 prostate cancer was not identified by MRI-targeted biopsy in 25/206 (12%) patients, and distributed fairly evenly across MRI scores. Of the cancers not detected using MRI-targeted biopsy, 3 (1.4%) patients had Gleason score 4+3, and 1 (0.4%) patient had Gleason score 4+4 prostate cancer.
A systematic and MRI-targeted biopsy strategy increases the detection of Gleason score ≥ 7 prostate cancer in patients managed with active surveillance. Further, a strategy that uses findings on MRI to avoid a biopsy would risk not identifying a small but relevant number of Gleason grade 3+4 cancers.
J Urol. 2016 Feb 23. pii: S0022-5347(16)00372-4. doi: 10.1016/j.juro.2016.02.084. [Epub ahead of print]
Written by: Recabal P1, Assel M2, Sjoberg DD2, Lee D3, Laudone VP4, Touijer K4, Eastham JA4, Vargas HA5, Coleman J4, Ehdaie B6
- 1Urology Service, Sidney Kimmel Center for Prostate and Urologic Cancers, Memorial Sloan Kettering Cancer Center, New York, NY, USA; Urology Service, Fundacion Arturo Lopez Perez, Santiago, Chile.
- 2Department of Epidemiology and Biostatistics, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
- 3Department of Urology, Weill-Cornell Medical College, New York Presbyterian Hospital, New York, NY, USA.
- 4Urology Service, Sidney Kimmel Center for Prostate and Urologic Cancers, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
- 5Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
- 6Urology Service, Sidney Kimmel Center for Prostate and Urologic Cancers, Memorial Sloan Kettering Cancer Center, New York, NY, USA; Department of Epidemiology and Biostatistics, Memorial Sloan Kettering Cancer Center, New York, NY, USA.