Objective: To assess progression and survival among patients with small-volume, well-differentiated, organ-confined prostate cancer found at radical retropubic prostatectomy (RRP), often defined as being 'insignificant', thus testing whether they are indeed 'insignificant'.
Patients and methods: We identified 6496 men treated for prostate cancer by RRP between 1990 and 1999, and defined 'insignificant' tumours as those in men having a prostate-specific antigen (PSA) level of < 10 ng/mL before RRP, a cancer volume of < or = 0.5 mL, a specimen Gleason of score < or = 6 and stage < or = pT2. Survival was assessed using the Kaplan-Meier method and compared using the two-sided log-rank test.
Results: 'Insignificant' tumours were found in 354 (5.5%) men, of whom only one had metastatic progression and none died from prostate cancer, with a median (range) follow-up of 9.2 (0.8-15.6) years. Biochemical progression-free survival (87% vs 85%, respectively, at 10 years, P = 0.5), systemic progression-free survival (100% vs 99%, P = 0.3), overall survival (91% vs 88%, P = 0.16) and cancer-specific survival (100% in each group, P = 0.32) were each similar among men with 'insignificant' prostate cancer and men with low-risk (defined by Gleason score, preoperative PSA level, seminal vesicle and surgical margin status) 'significant' cancer. Clinical stage, biopsy Gleason score and preoperative PSA doubling time were multivariably predictive of 'insignificant' tumours at RRP.
Conclusions: 'Insignificant' prostate cancer at RRP is associated with a comparable risk of biochemical progression as low-risk 'significant' cancer. Although clinical predictors for 'insignificant' pathology can be identified, it remains to be established whether such patients can be safely managed conservatively.