CLINICAL IMPACT OF IMPLEMENTING THE RECOMMENDATIONS OF AAPM TASK GROUP-43 ON PERMANENT PROSTATE BRACHYTHERAPY USING I-125

Purpose: To determine the clinical impact upon permanent interstitial prostate I-125 brachytherapy after conversion to AAPM Task Group 43 (T G 43) guidelines, Methods: The value of quantities used in the calcula tion of dose from two institutions, Northwest Tumor Institute (NWTI) a nd Memorial Sloan-Kettering Cancer Center (MSKCC), which pioneered int erstitial techniques for prostate brachytherapy were compared to those recently determined and published by TG 43 of the American Associatio n of Physicists in Medicine (AAPM). Using two different weighting sche mes, the change in the commonly prescribed reference dose of 160 Gy wa s determined and found to be in agreement with that recently suggested . Volumes encompassed by the reference isodose surface mere determined from a single source implant and a regularly distributed implant to s how the effect of change in reference dose, A comparative analysis on 10 patients was performed to show how this change affected common impl ant quality descriptors and the effect of changing the calculation for malism without changing the reference dose, Results: Both weighting sc hemes suggested a change in reference dose from 160 to 144 Gy. Single- source and distributed-source volumetric analysis confirmed this value , The effect on commonly used conformity and uniformity quantifiers fo r 10 implant patients was tabulated, Conclusion: Upon adopting the rec ommendations suggested by TG 43, institutions that perform permanent I -125 prostate implants using calculation methods adapted from the MWTI or MSKCC should revise their treatment prescriptions from 160 to 144 Gy so that the doses delivered to patients remain unaffected, Institut ions using other techniques to calculate dose should conduct an analys is similar to the one detailed here. (C) 1998 Elsevier Science Inc.