In this study of patients with prostate cancer, we explored associations between low prostate-specific antigen concentrations and disease progression and prognosis.

We retrospectively reviewed data of 233,554 prostate cancer patients in the SEER program and of 199 prostate cancer patients in the records of the Affiliated Hospital of Qingdao University with PSA ≤10 at diagnosis. The patients were stratified into 8 subgroups by T stage and Gleason score GS and survival curves for the resultant subgroups plotted using the Kaplan–Meier method. Multivariate Cox analyses were performed to investigate the effects of PSA concentrations in different subgroups. After randomly dividing patients into a training set and an internal validation set with a ratio of 7:3, a nomogram model to predict the survival of prostate cancer patients was established and validated.

Low PSA concentrations were significantly associated with advanced disease and poor prognosis in all prostate cancer patients with GS 8–10, whereas they were a protective factor in those with GS 6–7, Stage T1 disease. A nomogram model for predicting prognosis was established and validated. We obtained similar results with an external validation cohort.

We identified that low PSA concentrations have different impacts in prostate cancer patients with different T stages and GS. In patients with high GS, low PSA concentrations are a risk factor for progression to advanced disease and poor prognosis. A novel nomogram was established to predict survival of these patients.