Presentation Authors: Vignesh T. Packiam*, Stephen A. Boorjian, Matvey Tsivian, Laureano J. Rangel, Matthew T. Gettman, Igor Frank, R. Houston Thompson, Matthew K. Tollefson, Phillip J. Schulte, Rachel E. Carlson, John C. Cheville, R. Jeffrey Karnes, Rochester, MN
Introduction: Clinical Gleason score 8/Grade Group 4 (cGG4) prostate cancer (PCa) is characterized as high-risk and thereby, for men treated with radiation (RT), entails long-term androgen deprivation therapy (ADT). However, the potential for downgrading in Gleason score exists, and therefore characterization of risk factors for pathologic downgrading of cGG4 can potentially allow patients to be managed with intermediate risk RT/ADT protocols. Herein, we evaluate the incidence and predictors of downgrading among patients with cGG4 by assessing pathologic outcomes at radical prostatectomy (RP).
Methods: We reviewed our institutional prostatectomy registry to identify patients with cGG4 PCa who underwent RP between 2006-2017. Downgrading was defined as pathologic GG3 or less. Multivariable logistic regression assessed factors associated with downgrading. Survival was assessed using the Kaplan-Meier method.
Results: Of 244 patients, 118 (48%) were downgraded, of whom 73 were pGG3, 42 pGG2, and 3 pGG1. Patients with downgrading had similar age and clinical T-stage (p>0.05), but lower mean PSA (8.3 vs 11.6 ng/mL, p=0.048). Patients with downgrading were more likely to have a lower percent GG4 cores in the total (23% vs 37%) and positive (58% vs 80%) cores than those without downgrading (both p < 0.001). Increasing number of cores of GG4 was associated with decreased odds of downgrading (OR 0.76, 95%CI=0.67-0.87, p < 0.001). On multivariable analysis (Table 1), a higher number of GG1-GG3 cores was associated with increased odds of downgrading (OR 1.17), while a higher number of GG4 cores was associated with decreased odds of downgrading (OR 0.85, both p < 0.05). Median follow-up among survivors was 5.8 years (IQR 3.4-8.4), during which time 20 patients died, of whom 11 died of PCa. Patients with downgrading had significantly improved 10-year biochemical recurrence-free (66% vs 29%), systemic progression-free (75% vs 51%), PCa-specific (97% vs 84%), and overall survival (86% vs 74%) (all p < 0.05).
Conclusions: Nearly half of the patients with GG4 on core biopsy experience downgrading at RP. Pending validation, this information may be useful when counseling patients with cGG4 and risk factors for downgrading, especially when considering duration of ADT for those electing radiation.