Technical improvement in permanent seed implantation: a two-stage brachytherapy system. Description and comparison...

Permanent seed implantation by available techniques has modest limitations. A new, two-stage needle design and technique is described and evaluated in comparison to a conventional permanent seed technique.

The technique involves placing a stylet and sleeve initially into the all target coordinates prior to seed placement similar to temporary seed technique. The second stage involves consecutively removing the stylet from each sleeve and inserting a clear, plastic needle containing preloaded seeds into the sleeve and implanting the seeds. Fifty-six (125)I patients were treated with the two-stage technique. Comparisons were made with a cohort of 71 patients implanted using a conventional technique at the Seattle Prostate Institute. Prostate movement, surgical time, catheterization rate, and DVH postop dosimetry were analyzed.

After an initial learning curve, the two-stage technique had surgical times similar to conventional techniques. Cephalad movement of 3-10 mm was noted in 4 (8%) patients vs. 71 (100%) patients with our conventional technique. Of the 6 (10%) patients who required Foley catheterization, 3 (5%) did so for 1 day and 3 (5%) did so for less than 3 weeks. Day 1 CT scan based dosimetry was calculated on all patients. The V100 ranged from 80-100% with a median of 92.5%. For primary cases, the V100 (<85%) was 14% for the conventional vs. 7% for the two-stage technique. No two-stage patient had a V100 <80%. The V100 values for the two-stage and conventional techniques demonstrated a possible advantage with the two-stage technique (mean V100 92.6% vs. 90.7%, [p=0.051]). The D90 for the two-stage technique ranged from 123-190 Gy with a median of 151.5 Gy for implant only and a median of 127 Gy for boost cases. The D90 values for the two-stage patients were slightly but not statistically better than the conventional technique (p=0.232). Thirty-one percent of conventional technique patients had a D90 <140 Gy vs. 22% for two-stage technique.

This new two-stage brachytherapy technique may offer some advantages over conventional techniques including: simple and improved needle loading verification, less complicated and better visualization of needle placement, improved stabilization of the gland, and more consistent postoperative dosimetry.