For this study, the authors reviewed the medical record and images of 366 high-risk and very high-risk prostate cancer patients that had pre-operative mpMRI staging and underwent radical prostatectomy between 2006 and 2015 at a single institution. Staging mpMRI was considered positive if there was any evidence of seminal vesicle invasion, extraprostatic extension, or neurovascular bundle involvement. A multivariable logistic regression model was used to assess for factors associated with pT2 stage; a multivariable Cox proportional hazards model was used to assess for factors associated with time to biochemical failure.
In this cohort, there were 223 high-risk (60.9%) and 143 very high-risk (39.1%) men with prostate cancer. Patients with very high-risk disease had Gleason 10 prostate cancer in 6% of cases (vs 0% in high-risk patients), and 55% and 35% Gleason 9 and 8, respectively (compared to 17% and 60% for high-risk patients, respectively). Patients with high-risk disease were more likely to have a negative mpMRI compared to very-high risk patients (63% vs 38%, p<0.001). Patients with high-risk disease were also more likely to have pT2 disease (50% vs 20%, p<0.001).
In the overall cohort, predictors of pT2 disease were:
- Lack of positive staging mpMRI (OR 0.3, 95%CI 0.2-0.6)
- Lower PSA (OR 0.96, 95%CI 0.94-0.98)
- Fewer cores of Gleason score >8 cancer (OR 0.84, 95%CI 0.75-0.94)
When considering only high-risk patients, lack of positive mpMRI (OR 0.4, 95%CI 0.2-0.7) and lower PSA (OR 0.92, 95%CI 0.88-0.97) were still associated with pT2 disease. When considering very-high risk patients alone, only lack of positive staging mpMRI (OR 0.3, 95%CI 0.13-0.72) was associated with pT2 disease. Downstaging to pT2 (HR 0.70 95%CI 0.4-1.2,) or positive staging mpMRI (HR 1.2, 95% 0.8-1.7) were not independently associated with time to biochemical failure.
What is somewhat surprising is that despite mpMRI technology, 37% of very-high risk and 62% of high-risk patients had a completely negative mpMRI. The strength of this study is the application of mpMRI technology to further refine patient selection for patients that may be the likeliest to benefit from aggressive local therapy. A possible limitation of the study is the potential lack of generalizability of the findings, considering that all high-risk patients were required to obtain an mpMRI and require expert radiology interpretation of the findings (ie. nuances of seminal vesicle invasion and neurovascular bundle invasion). Based on their findings. Dr. Reichard concluded that a negative staging mpMRI was most strongly associated with pathologic organ confined disease, whereas fewer positive cores of Gleason >8 cancer and lower PSA were also associated pT2 disease. Certainly, these findings require further validation and may provide the necessary framework to select patients for clinical trials evaluating multi-modal treatment in high risk prostate cancer.
Presented by: Chad A. Reichard, MD Anderson Cancer Center, Houston, TX
Co-Authors: Justin R. Gregg, Tharakeswala Bathala, Mary F. Achim, Quynh-Nhu Nguyen, John W. Davis, Brian F. Chapin, Houston, TX
Written by: Zachary Klaassen, MD, Urologic Oncology Fellow, University of Toronto, Princess Margaret Cancer Centre, Twitter: @zklaassen_md, at the 2018 AUA Annual Meeting - May 18 - 21, 2018 – San Francisco, CA USA