Login to Access Video or Poster Abstract: MP20-01
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Introduction

In the recently published 8^th edition update of the AJCC staging system for prostate cancer (PCa), pT2a/b/c sub-classifications were consolidated as pT2. Also, serum prostate-specific antigen (PSA) ≥20ng/ml or Grade Group (GG) 5 now classify patients as Stage III disease. We sought to validate these changes in a large institutional registry with long-term follow-up.

Methods

Men who underwent radical prostatectomy without prior therapy at Mayo Clinic between 1987-2011 were identified. The prognostic significance of a single pT2 designation was compared to previous stratification as unilateral (pT2a-b) versus bilateral (pT2c). Further, 7^th edition Stage II patients were then re-categorized based on the presence or absence of PSA ≥20ng/ml and GG 5. Biochemical recurrence-free (BCR) survival, systemic progression-free survival (sPFS), and cancer-specific survival (CSS) were evaluated using Kaplan Meier analyses and multivariable Cox regression models, adjusting for age, Gleason score, preoperative PSA, and surgical margin status.

Results

The overall cohort included 17,846 men with a median follow-up of 11 years (IQR 7,16), during which time 5021 experienced BCR, 1246 progressed systemically, and 641 died from PCa. Among pT2 patients, sub-stratification was not independently associated with BCR-free survival (HR=1.0; 95%CI 0.9-1.1; p=0.69), sPFS (HR=1.0; 95%CI 0.8-1.3; p=0.68), or CSS (HR=0.9; 95%CI 0.6-1.2; p=0.41). Meanwhile, patients previously classified with Stage II disease who had a preoperative PSA ≥20ng/ml (now Stage III) had a 15-year CSS that was significantly worse than Stage group II patients with PSA < 20ng/ml (88% vs 94%; p<0.001), but similar to 7^th edition Stage III patients (88% vs 86%; p=0.12). On the other hand, Stage II patients now classified as Stage III based on GG 5 had a 15 year CSS that was significantly worse than both 7^th edition Stage II patients with GG 1-4 (48% vs 68%; p<0.001) and 7^th edition Stage III patients (48% vs 60%; p<0.001). Results for BCR-free survival and sPFS were similar.

Conclusions

We validate the new AJCC pT2 staging classification. Moreover, our data support the designation of patients with a PSA ≥20ng/ml as Stage III disease. Interestingly, while upstaging GG5 patients from Stage II to III is an improvement, these patients have even worse outcomes than 7^th edition Stage III patients, emphasizing the particular prognostic significance of the new GG and the importance of including GG in staging classification.

Funding

none