Contemporary validation of cT1a vs. cT1b substaging of incidental prostate cancer

The cT1a vs. cT1b substratification was introduced in 1992 but never formally tested since. We tested the discriminative ability of cT1a vs. cT1b substaging on cancer-specific survival (CSS) in contemporary incidental prostate cancer (PCa) patients. Incidental (cT1a/cT1b) PCa patients were identified within the Surveillance, Epidemiology, and End Results (SEER) database (2004–2015). Kaplan–Meier estimates, as well as uni- and multivariable Cox regression models predicted CSS at five years. Subgroup analyses addressed CSS at five years according to active vs. no local treatment (NLT) as well as Gleason score sum (GS; 6 vs. 7 vs. ≥ 8). We identified a total of 5,155 incidental prostate cancer patients of which 3,035 (59