Interstitial low-dose-rate mono-brachytherapy with I125 - relapse-free survival and dosimetric outcome for localised prostate cancer in a single European institution
Neubauer S1,2,Derakhshani P1,2, Weise C1,3, Spira G1,3
(1) West German Prostate Center, Cologne, Germany
(2) Department of Urology, Klinik am Ring, Cologne
(3) Department of Radiooncology, Klinik am Ring, Cologne
Introduction and Objective:
To report tumor control and correlation to dosimetric results for patients with localized prostate treated with I-125 permanent seed implantation in a single European institution. This paper reports preliminary data on PSA outcome with a follow-up of up to 7 years.
Materials and methods:
651 patients with localised prostate cancer at stage T1-T2 received transperineal seed implantation with real-time intraoperative planning as monotherapy between December 2000 and December 2004 and were eglible for statistical analysis.
A total of 501 (76.9%) patients met the low-risk group definition, 148 (22.8%) were in the intermediate-risk and 2 (0.3%) in the high-risk group. Gleason score 6 or less was found in the majority of patients (n=599/92%) and clinical stage was T1a-b in 1.4%, T1c in 68%, T2a in 27% and T2b in 1.1%.
Median follow-up time was 52.7 (range: 35.3-84.0) months. The 5-year PSA relapse-free survival (PRFS) outcome for low-risk and intermediate-risk patients according to the ASTRO definition was 97.5% and 94%, respectively. Median V100 Prostate was 98% and a median D90 Prostate of 177 Gy was achieved. The D90 was >130/140/150/160 Gy in 98.2/93.9/90.4 and 85.6% of patients. The median urethral D30 was 199.3 Gy and D10 rectal dose was 88.2 Gy. Patients with PSA-relapse were found to have a median D90 of 167.8 Gy, whereas the patients with PRFS had a median D90 of 175.9Gy. Patients were stratified to PSA nadir 0.5 ng/mL with the 5-year PRFS being 98.2% and 87.6%. Subanalaysis of the low-risk group showed a 5-year PRFS for PSA nadir 0.5 ng/mL of 97.9% and 92.1%.
The results of our study show that outcome of permanent seed implantation relates to pre-treatment PSA, tumor stage, Gleason score and dosimetric quality. A PSA nadir < 0.5 ng/mL was strongly related to long-term PSA relapse-free survival. In our series D90 Prostate, as a reflection of implant quality, was the strongest factor that impacts outcome.The use of real-time intraoperative planning optimizes high dose coverage of the target and can achieve an optimal therapeutic ratio between prostate and structures at risk. Biochemical control outcomes were excellent at 5 years and showed that the American data can be reproduced by European high-volume centers.