First Report on the Use of a Thinner I125 Radioactive Seed that Fits into 20 Gauge Needles for Permanent Seed Prostate Brachytherapy: A Report on Post-implant Dosimetry and Acute Toxicity
Accepted for future publication of the 51st ASTRO Annual Meeting Nov. 1-5, 2009
Authors: Jason Wong, John E. Sylvester, Peter D. Grimm, et al.
Purpose: Standard prostate brachytherapy (PB) seeds fit into 18 gauge (G) needles. In Aug 2008 a thinner 125I seed was introduced. These new seeds fit into 20G needles. The purpose of using thinner needles is to minimize trauma to the patient during PB. This study compared the post-PB dosimetry and acute toxicity between the use of standard seeds in 18G needles and thinner seeds in 20G needles.
Methods and Materials: The first part of the study was a retrospective post-PB dosimetric comparison of 100 consecutive PB patients treated with (Oncura Inc. model 9011 ThinStrand™) 20G needles to 100 consecutive PB patients treated with standard 18G PB needles. Urinary retention rates and dosimetric variables were evaluated. The second part was a prospective survey study to assess acute toxicity. 22 consecutive patients treated with 20G needles were compared with 22 consecutive patients treated with 18G needles in the same time period. All patients were followed with patient administered surveys on post-PB day 1 and telephone surveys on day 7. Endpoints include dysuria (on scale of 0-10), hematuria (scale=1-5), perineal pain/bruising (scale=0-10) and international prostate symptom scores (IPSS). In both parts, patients were treated using the Seattle pre-plan technique and had 125I PB alone as primary treatment for prostate cancer. Unpaired t-tests were used to compare differences between the 18G and 20G cohorts.
Results: Baseline characteristics including preimplant prostate volumes and IPSS were similar between the two cohorts. In the post-PB dosimetric comparison between the 20G and 18G group, the V100 (95 vs 91(%)), D90 (161 vs 149 (Gy)), V150 (55 vs 45 (%)) and RV100 (0.43 vs 0.30 (cc)) were all statistically significantly (p<0.0004) higher in the 20G group. With a minimum follow-up of 30 days, urinary retention rates were 8% and 7%, median catheter-dependent durations were 7 and 14 days, and median time from PB to retention was 4 and 7 days for the 20G and 18G groups respectively. In the prospective study on acute toxicity, no statistical significance was found for dysuria, hematuria or IPSS scores between the two cohorts. However, there were statistically significant differences (p<0.04) in perineal bruising post-PB day 1 (3 vs 2) and pain scores on day 1 (3 vs 1.5) and day 7 (1.1 vs 0.5) between the two groups- all favoring the 20G group.
Conclusion: The use of thinner 125I seeds in 20G needles for prostate brachytherapy had comparable urinary retention rates and improved post-PB dosimetry when compared to standard 125I seeds in 18G needles. Patients treated with the thinner 125I seeds in 20G needles had less severe post-PB perineal pain and bruising. A randomized trial is now being conducted to confirm these results.