Permanent prostate brachytherapy monotherapy with I-125 for low- and intermediate-risk prostate cancer: Outcomes in 974 patients

Purpose: To report outcomes of patients undergoing low-dose-rate (LDR) brachytherapy and investigate factors associated with biochemical failure and survival.

Methods: Consecutive patients undergoing LDR with I-125 at our institution between 1998 through 2013 for primary intact prostate cancer were examined. Those with low- and intermediate-risk disease receiving LDR with a minimum of 2 years followup and at least one post-LDR prostate-specific antigen (PSA) were included.

Results: About 974 patients satisfied inclusion criteria. With median followup of 72 months, biochemical failure occurred in 45 patients. Freedom from biochemical failure as defined by the Phoenix criterion was 96% and 88% at 5 and 10 years, worse for intermediate risk as compared with low risk, with 10-year freedom from biochemical failure of 76% versus 92% (hazard ratio [HR] = 3.7, p < 0.001), respectively. On multivariable analysis, increased prebiopsy PSA, Gleason 4 + 3, and no androgen deprivation therapy were associated with biochemical failure. Gleason 4 + 3 was the factor most strongly associated with biochemical failure (HR = 7.01, p < 0.001). No examined factors were associated with local failure. Gleason 4 + 3 disease increased the likelihood of distant metastasis (HR = 12.4, p = 0.003) and prostate cancer-specific death (HR = 13.2, p < 0.001). No difference in outcomes between patients with Gleason 3 + 3 versus 3 + 4 was observed.

Conclusions: LDR brachytherapy provided excellent outcomes in this large series of patients treated for localized organ-confined prostate cancer. Local recurrence at 10 years was low at 2.1%. Primary Gleason 4 + 3, higher pretreatment PSA, and no receipt of androgen deprivation therapy were the only factors associated with biochemical failure. Primary Gleason 4 disease was also predictive of distant metastases and decreased prostate cancer-specific survival.