POSTTREATMENT BIOPSY RESULTS FOLLOWING INTERSTITIAL BRACHYTHERAPY IN EARLY-STAGE PROSTATE-CANCER

Purpose: To assess pathologic control rates for prostatic carcinoma as determined by postimplant prostate biopsy in a large series of consec utive patients who have received permanent interstitial brachytherapy using a contemporary transrectal ultrasound-directed, transperineal, c omputer generated, volume technique. Methods and Materials: Four hundr ed and two patients received permanent I-125 or Pd-103 interstitial br achytherapy as primary treatment for early stage prostatic carcinoma a t the Northwest Tumor Institute between January 1988 and January 1994, Of these, 201 have consented to biopsy 12 or more months postimplant with a median follow-up of 40 months (range: 12-83 months), None had r eceived hormonal manipulation, A total of 361 biopsies was performed o n 201 patients with a range of one to six annual biopsies per patient (91 received multiple, serial biopsies), Of the 161 patients more than 12 months postimplant who have not been biopsied, most have been unwi lling or unable to submit to biopsy, Only six patients with biochemica l progression have not been biopsied, There was no difference in the p resenting characteristics or implant parameters between those patients biopsied and those that were not, One hundred and forty-three receive d I-125 (71%) prescribed to a MPD of 160 Gy with a median activity of 35.5 mCi, and 58 (29 %) received (103)pd prescribed to a MPD of 115 Gy with a median activity of 123 mCi, Multiple biopsies were performed u nder transrectal ultrasound guidance, and all specimens were classifie d as either negative, indeterminate, or positive. Results: At the time of last biopsy, 161 (80%) have achieved negative pathology, 34 (17%) remain indeterminate, and 6 (3%) have been positive, Only 2 of the 186 patients with a PSA < 4.0 ng/ml at the time of biopsy were positive, Among those 33 indeterminate patients with a subsequent biopsy, 28 hav e converted to negative, 2 to positive, and 3 remain unchanged to date . Conclusions: These data demonstrate at least an 80% pathologically c onfirmed local control rate following permanent interstitial brachythe rapy for early stage prostate cancer, A higher local control rate is e xpected with further follow-up as the majority of indeterminate biopsi es convert to negative over time, The indeterminate category of postir radiation biopsy described here includes specimens that have probably been interpreted as positive in other series, but correlate clinically and biochemically with negative biopsies, These results support the u se of modern interstitial brachytherapy techniques for selected patien ts with early stage adenocarcinoma of the prostate. Copyright (C) 1997 Elsevier Science Inc.