A preoperative nomogram is an effective tool for assessing the risk of disease progression after radical prostatectomy for localized prostate cancer. To better understand the performance of nomograms for patients with a low prostate-specific antigen (PSA) level, we examined whether patients with a PSA level <2.5 ng/mL had outcomes different than predicted by a validated preoperative nomogram.

A cohort of 6130 patients from 2 referral centers was analyzed. Kaplan-Meier methods were used to estimate the recurrence-free probabilities stratified by PSA group (<2.5 vs ≥2.5 ng/mL). Cox proportional hazards regression analysis was used to evaluate whether the PSA grouping was associated with biochemical recurrence, controlling for preoperative nomogram probability.

Of 6130 patients, 399 (6.5%) had a PSA level <2.5 ng/mL. Patients with a PSA level of ≤0.5 ng/mL had a high rate of nonorgan-confined disease (33% vs 15% for PSA levels of 0.6-2.5 ng/mL). The median follow-up for recurrence-free patients was 2.4 years, and 10 patients with a PSA level of <2.5 ng/mL and 597 patients with a PSA level >2.5 ng/mL developed recurrence (total 607/6130). With adjustment for the preoperative nomogram probability, no significant difference was found in recurrence by PSA grouping (hazard ratio 0.78 for PSA <2.5 vs ≥2.5 ng/mL; 95% confidence interval 0.42-1.48; P = .5).

Patients with a low PSA comprise a small proportion of those treated, and most have palpable disease. Patients with especially low PSA values (≤0.5 ng/mL) have a high rate of nonorgan-confined disease. We saw no evidence that patients with low PSA levels have worse outcomes, after the stage and grade were taken into account.