Validation of the updated eighth edition of AJCC for prostate cancer: Removal of pT2 substages - Does extent of tumor involvement matter?

Background: Updates in the eighth edition of the AJCC prostate cancer staging manual include removal of the organ-confined (pT2) substages.

Methods: Retrospective analyses of 12,028 pT2 patients that underwent radical prostatectomy between 2003 and 2016 and did not receive neo- or adjuvant treatments. Kaplan-Meier curves as well as multivariable Cox-regression analyses compared biochemical recurrence (BCR), metastatic progression (MP) and overall mortality (OM) between the 3 subcategories (pT2a, pT2b and pT2c).

Results: After surgery, 1,441 patients were classified as pT2a, 126 as pT2b and 10.495 as pT2c. Five-year BFS rates for pT2a, pT2b and pT2c were 92.0% vs. 97.4% vs. 88.0%. For the same groups, 5-year MP-FS rates were 99.5% vs. 100% vs. 99.0% and 5-year OS rates were 98.0% vs. 98.2% vs. 97.7%. In multivariable analyses pT2 substratification did not reach independent predictor status for biochemical recurrence, MP or overall mortality.

Conclusions: Substratification of pT2 prostate cancer was not predictive for further disease progression. Therefore, removing the substages simplifies the staging system without loss of important information.