Outcomes following iodine-125 brachytherapy in patients with Gleason 7, intermediate risk prostate cancer: a population-based cohort study

Background and purpose: To evaluate outcome in patients with Gleason 7 prostate cancer treated with iodine-125 brachytherapy at the British Columbia Cancer Agency.

Materials and methods: Between 20th July 1998 and 7th February 2006, 1500 patients underwent I-125 prostate brachytherapy without supplemental external beam radiation therapy. Of these, 439 had Gleason 7 disease; 362 had Gleason 3+4 and 77 had 4+3 disease. Generally, patients received 6 months of androgen suppression. We compared biochemical no evidence of disease (bNED) between patients with Gleason ≤ 6 and Gleason 7 and between Gleason 3+4 and 4+3 using the Phoenix definition of biochemical recurrence.

Results: Median follow-up was 60 months. Estimated 5 year bNED was 97% for patients with Gleason score ≤ 6 and 94% for patients with Gleason 7 disease (p=0.037). Estimated bNED was 95% and 94% for 3+4 and 4+3, respectively (p=0.791). There was no difference in bNED between implants achieving D90 ≥ versus<the median value (150.5 Gy) or ≥ versus<140 Gy.

Conclusions: I-125 brachytherapy with 6 months of ADT demonstrates excellent bNED rates in Gleason 7 disease. We found no evidence of a difference between patients with Gleason 3+4 versus 4+3 disease.