Significance of normal serum prostate-specific antigen in the follow-up period after definitive radiation therapy for prostatic cancer

To determine the prognostic significance of a normal serum prostate-specific antigen (PSA) level in patients with prostatic cancer with long-term follow-up evaluation after radiotherapy. PSA information was available in 403 patients (38%) who were treated with pelvic lymph node dissection and retropubic radioactive iodine-125 implantation. One hundred eighty-two patients had a normal serum PSA level (< or = 4.0 ng/mL) the first time this test was conducted during the follow-up period, designated PSA-1. Among patients with PSA-1 values < or = 1.0 ng/mL, the 5-year PSA relapse-free survival rate was 85% compared with 27%, respectively, among those with PSA values in the higher range of normal (P < .00001). Multivariate analysis demonstrated that only a PSA-1 value greater than 1.0 to < or 4.0 (P < .00001) and grade II/III histology (P = .009) had a negative impact on continued PSA relapse-free survival. The only independent variable identified by a multivariate analysis to affect local relapse-free survival (LRFS) was a PSA-1 value greater than 1.0 to < or = 4.0 ng/mL (P < .004), while high-grade histology (P < .0001) and local failure (P < .001) were the only significant variables to affect distant metastases-free survival (DMFS). Patients with PSA values < or = 1.0 ng/mL are significantly less likely to have a subsequent relapse after therapy than those with levels greater than 1.0 to < or = 4.0 ng/mL. Continuously maintained PSA levels of < or = 1.0 ng/mL after treatment may serve as an end point for early evaluation of the efficacy of experimental radiotherapy protocols in prostate cancer.