Risk profiles to predict PSA relapse-free survival for patients undergoing permanent prostate brachytherapy.

Purpose: Combined risk profiles are helpful in assessing the likelihood of prostate-specific antigen relapse-free survival (PSA-RFS) for patients with localized prostate cancer. This retrospective analysis reports the 5-year biochemical outcome of a large cohort of patients according to prognostic factors and risk profiles for patients undergoing ultrasound-guided transperineal interstitial permanent prostate brachytherapy (TIPPB).

Patients and methods: Seven hundred seventeen consecutive patients with clinically localized prostate cancer treated between June 1992 and November 1997 underwent TIPPB. Palladium-103 (103Pd) (n = 539) or iodine-125 (125I) (n = 178) sources were utilized to a prescribed dose of 120 Gy and 144 Gy, respectively. One hundred eleven patients received combined external-beam irradiation (41.4 or 45 Gy) and TIPPB (103Pd, 90 Gy, and 125I, 108 Gy). One hundred twelve patients received androgen ablation therapy in advance of TIPPB. Patients were grouped into risk profiles based on pretreatment factors that consisted of PSA < or = 10 and Gleason score < or = 6. Patients meeting both criteria were classified as favorable (n = 334). Those not fulfilling one criteria were classified as intermediate risk (n = 261), and those not fulfilling two criteria were classified as unfavorable risk (n = 261). PSA-RFS was calculated based on the American Society of Therapeutic Radiology and Oncology consensus conference definition of PSA failure. The median follow-up was 41 months (range, 14-82 months).

Results: The actuarial PSA-RFS survival at 5 years was 82%. Multivariate Cox regression analysis identified PSA and Gleason score as highly significant factors predicting for biochemical outcome. Hazard risk ratios using a nadir definition of the PSA as < or = 1.0 ng/mL and < or = 0.5 ng/mL were each significant predictors of outcome with the 0.5 ng/mL nadir level only slightly better (risk ratio for nadir < or = 1.0 = 2.78; risk ratio for nadir < or = 0.5 = 3.57). Favorable-risk patients had a 5-year actuarial PSA-RFS of 93%, whereas intermediate-risk and unfavorable-risk groups had 5-year PSA-RFSs of 77% and 62%, respectively. Four hundred ninety-three patients underwent brachytherapy without external-beam irradiation or androgen ablation. From this group, the 5-year PSA-RFSs for the favorable-risk, intermediate-risk, and unfavorable-risk patients were 92%, 74%, and 55%, respectively.

Discussion: This retrospective study examining TIPPB demonstrated excellent 5-year actuarial PSA-RFS rates. The assignment of risk profiles based on the results of multivariate analysis of prognostic factors identifies the expected PSA-RFS for patients undergoing TIPPB.