Analysis on the Reporting of Medical Events in Permanent Prostate Brachytherapy

Abstract

Purpose: In February 2012, the Nuclear Regulatory Commission (NRC) Advisory Committee on the Medical Use of Isotopes (ACMUI) recommended a source strength-based criterion defining a medical event (ME) in permanent brachytherapy as a procedure with greater than 20% of the sources falling outside the treatment site. A review is performed on prostate seed implants reported as MEs to regulatory agencies, aiming to analyze the nature of the events and the impact of the rulemaking on the practice of permanent prostate brachytherapy. Methods and Materials: MEs in permanent prostate brachytherapy reported to regulatory agencies from 1999 to 2012 are reviewed and divided into three categories based on the nature of the events and the reporting methods. Results: A total of 346 prostate seed implants were reported as MEs to NRC or agreement states from 1999 to 2012. The events consist of: (i) incorrect source strength/planning error (n = 32); (ii) seed/needle misplacement or excessive dose to normal tissue/organ (n = 104); and (iii) discrepancy in dose to target (n = 210). Many MEs are due to prostate volume expansions which occur after the implant procedures. Application of the recommended rules would eliminate these cases wrongly categorized as MEs. Conclusions: Methods used for evaluating and reporting MEs in permanent prostate brachytherapy have been inconsistent over time. It is challenging to determine MEs based on dose or seed distributions without infringing on AUs’ practice of medicine. The use of post-implant dosimetry for regulatory compliance purposes places the technique of permanent brachytherapy under a high level of scrutiny and has resulted in a large number of MEs after 2008 under the current dose-based standard. The practice of permanent prostate brachytherapy is, therefore, detrimentally affected. Many of these implants would not be classified as MEs when a source strength-based standard is used, as recommended recently by ACMUI. Regulations should be patient outcome and impact-based by taking into account the differences in treatment and QA procedures in various radiation therapy modalities. Unless post-implant dosimetry is used strictly for QA purposes, establishment of a source strength-based ME standard for permanent brachytherapy with a 50% allowance for seeds falling outside the treatment site is warranted in order to maintain a balance in regulatory oversight of all treatment techniques. In addition, well-balanced regulations must be accompanied by rigorous institutional QA programs with the goal that high quality implants are consistently achieved and prostate cancer patients receive the full benefit from their permanent brachytherapy treatments.