SU-GG-T-76: Post Implant Dosimetry for I 125 and Pd 103 Anchor and Non Anchor Seeds

Abstract

Purpose: The purpose of this study is to investigate if there is a significant difference between the post implant dosimetry of the anchor and non anchor seeds for both I‐125 and Pd‐103. Method and Materials: The post implant plans of 40 patients treated during 2008 – 2009 in our institution were analyzed. 10 patients were treated for each of the following seeds; I‐125 ancer seeds I‐125 anchor seeds (BrachySciences, Inc. Oxford, CT)a Pd‐103 anchor seeds (BrachySciences, Inc. Oxford, CT) and Pd‐103 non anchor seeds (Theragenics Corporation® Buford, GA). Advantage I‐125™ Seed (Model IAI‐125A) and Theraseed Pd‐103™ Seed (Model 200) were the seed models used for I‐125 and Pd‐103 respectively. Besides having a ribbed structure, the anchor seeds are encapsulated with a bioabsorbable polymer which is designed to help aid fixity (see figure 1). The preplan criteria for all implants were the same. All seeds were loose seeds implanted using a Mick applicator. A seed localizing scan was acquired 30 days post the implant. Dose levels that cover 100% (D100) and 90% (D90) of prostate were determined. In addition, the fraction of the prostate volume receiving 200% (V200), 150% (V150), 100% (V100) of the prescribed dose were also evaluated. Results: The differences in D100, D90, V100, V150 and V200 for the patients in this study for the anchor and non‐anchor seeds for both I‐125 and Pd‐103 are statistically insignificant. It may be possible that if different dosimetric quality indicators are studied then a difference may be more visible. Conclusion: We did not observe a statistically significant dose difference in the post implant dosimetry between the anchor and non — anchor seeds for the patients included in this study. Future works on sector analysis may be able to provide more information on differences resulted from using anchor seeds.