Prediction of Organ-confined Disease in High- and Very-high-risk Prostate Cancer Patients Staged with Magnetic Resonance Imaging: Implications for Clinical Trial Design

Background: High-risk (HR) prostate cancer (PCa) is a heterogeneous disease leading to difficulties in designing appropriate inclusion criteria for clinical trials. Objective: To describe clinical predictors of organ-confined disease in HR or very-high-risk (VHR) PCa patients staged with multiparametric magnetic resonance imaging with endorectal coil (mp-MRI-ER). Design, setting, and participants: We reviewed 366 HR/VHR PCa patients who had preoperative mp-MRI-ER, and underwent radical prostatectomy and extended pelvic lymph node dissection between 2006 and 2015. Intervention: Radical prostatectomy with preoperative mp-MRI-ER. Outcome measurements and statistical analysis: We used multivariable logistic regression modeling to assess for associations with ≤ pT2N0 stage and multivariable cox modeling to assess for associations with biochemical failure. Results and limitations: Of 366 patients, 132 had ≤ pT2N0 disease. For the entire cohort, negative staging mp-MRI-ER (odds ratio [OR] 1.73, 95% confidence interval [CI] 1.06–2.83, p = 0.03), lower prostate-specific antigen (PSA; OR 0.98, 95% CI 0.97–1.00, p = 0.02), and fewer cores of Gleason ≥8 cancer (OR 0.86, 95% CI 0.79–0.93, p = 0.0002) were associated with ≤pT2N0 disease. In HR patients only, negative mp-MRI-ER (OR 3.41, 95% CI 1.73–6.72, p = 0.0004) and fewer than four cores of Gleason ≥8 disease (OR 3.38, 95% CI 1.20–9.56, p = 0.02) were still associated with ≤pT2N0 disease. Lack of non–organ-confined disease on MRI was associated with superior biochemical recurrence-free survival (p = 0.02). Limitations of this study include lack of a central review or quality control of the MRI reporting. Conclusions: In HR PCa, negative staging mp-MRI-ER, fewer positive cores of Gleason >8, and lower PSA were significant predictors of pathologic organ-confined disease. Improved prediction of organ-confined disease in HR patients may allow for their inclusion into studies evaluating treatments from which they would otherwise be excluded based solely on their HR status. Patient summary: In patients with high-risk prostate cancer, prostate magnetic resonance imaging along with other clinical parameters may help determine which patients are likely to have disease confined to the prostate and thus be eligible for clinical trials that they otherwise might be excluded from based on their high-risk status alone. Improved prediction of organ-confined disease in high-risk (HR) prostate cancer patients may allow for their inclusion into studies evaluating treatments from which they would otherwise be excluded, based solely on their HR status.