Recommendations for permanent prostate brachytherapy with 131Cs: A consensus report from the Cesium Advisory Group•☆☆
Abstract
Purpose
Published clinical information on the safety and efficacy of 131Cs implants is limited. We provide consensus recommendations for 131Cs prostate brachytherapy based on experience to date.
Methods and Materials
The Cesium Advisory Group (CAG) consists of experienced 131Cs users. Recommendations are based on three clinical trials, one of which has completed accrual and has been published in the peer reviewed literature, and combined CAG experience of more than 1200 131Cs implants.
Results
We recommend using 1.059
cGyh−1U−1 as the dose rate constant for the IsoRay source. The prescription for monotherapy implants is 115Gy and when combined with 45–50Gy external beam it is 85Gy. Suggested individual source strength ranges from 1.6 to 2.2U.
The release criterion for 131Cs implants is 6mRh−1 at 1m.
131Cs brachytherapy should be performed differently from 125I and 103Pd brachytherapy: source placement is further from the urethra and rectum; the prostate V150 should be ≤45%; sufficient margins may be obtained while limiting source placement to the capsule or close to the capsule.
The increased dose rate may cause degradation of postimplant quantifiers due to edema. However, large variability in the magnitude and rate of resolution of edema make determination of the most representative postoperative imaging time impossible. The CAG recommends postimplant imaging on the day of the implant.
Recommended postimplant evaluation goals include prostate D90 greater than the prescription dose; maintaining Du,30<140% of the prescription dose and keeping Vr,100<0.5cm3.
Conclusion
It was the consensus of the CAG that optimal 131Cs implants should be performed differently from those performed with 125I or 103Pd. Guidelines have been established to allow for safe and effective delivery of 131Cs prostate brachytherapy.
Keywords: Cesium, Prostate brachytherapy, Implants, Dosimetry, Clinical results
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• Financial disclosure: The randomized trials included in this report were supported by research grants from IsoRay Medical, Richland, WA (IsoRay). When necessary, travel to attend one CAG meeting was provided by IsoRay. An honorarium was paid by IsoRay to some of the members to attend one of the meetings (SB, BM, RP, MR). Several members are paid consultants for IsoRay (BP, MR, SK, RP). None of the authors are employees, none have received any stock ownership, nor provided expert testimony, nor patent applications for IsoRay.
☆☆ Although IsoRay provided funding for the clinical trials referred to in the report, IsoRay provided no assistance with study design, data collection, analysis, data interpretation, report writing, or decision to submit the report for publication.
PII: S1538-4721(08)00589-8
doi:10.1016/j.brachy.2008.05.004
© 2008 Published by Elsevier Inc.
