Purpose: Active surveillance is an accepted standard of care for patients with Gleason score 6 prostate cancer. However, many choose radical treatment given a 20%-25% probability of occult higher grade disease. Although Epstein criteria is commonly used to predict this probability, its accuracy can be poor and does not eliminate overtreatment. Meanwhile, multiparametric MRI (mpMRI) rules out higher grade disease with > 90% negative predictive value and can facilitate targeted biopsies of suspicious areas. It has the potential to emerge as a preferred risk-stratification strategy at initial presentation to help men who wish to delay and/or avoid the risks of treatment.
Methods: As of May 2013, 57 consecutive men with Gleason score 6 prostate cancer referred to our radiation oncology service underwent a 3T-mpMRI of the prostate with body coil to complete their staging. Findings were reviewed at a dedicated monthly multi-disciplinary prostate cancer conference, including radiology, radiation oncology, and urology. All patients with a suspicious finding on mpMRI underwent an image-guided targeted biopsy through the perineum with MRI-ltrasound image fusion software (MIM Symphony).
Results: More than half (31 out of 57) of patients were considered ineligible for active surveillance when applying Epstein criteria, yet only 18% had a suspicious radiographic finding concerning for higher grade disease. Among patients with eligible vs ineligible by Epstein criteria, the rate of abnormal mpMRI scans was 11% vs 23%, respectively (P = .32). Final pathologic findings revealed Gleason score 7-10 in 60% of targeted biopsies. The number of patients needed to scan to confirm a higher grade lesion was 26 vs 7 (P < .001), respectively. All men (100%) based their management decisions on the results of mpMRI with targeted biopsies when indicated, and the overall rate of active surveillance was 89%. The rate active surveillance among those traditionally considered eligible vs ineligible by Epstein criteria was 96% vs 84% (P = .21), respectively.
Conclusions: Patients with Gleason score 6 prostate cancer have readily adopted the results of mpMRI, with targeted biopsies when indicated, as a preferred source of information to help them with the decision to choose active surveillance. This strategy helped 84% of patients traditionally considered “ineligible for active surveillance” by Epstein criteria delay and/or avoid the risks of treatment. Efforts should be made to make this technology more widely available, given the number of patients it can affect.