Improved biochemical control and clinical disease-free survival with intraoperative versus preoperative preplanning for transperineal interstitial permanent prostate brachytherapy.

PURPOSE

We hypothesized that intraoperative preplanning for transperineal interstitial permanent prostate brachytherapy may yield better prostate cancer control than preoperative preplanning. We tested this hypothesis by comparing treatment outcomes of patients who underwent implantation using these two preplanning methods.

PATIENTS AND METHODS

We analyzed the data of 135 consecutive patients with localized prostate cancer treated from 1996 to 2001 with transperineal interstitial permanent prostate brachytherapy+/-preimplantation hormonal therapy: 42 received preoperative preplanning (group 1), and 93 underwent intraoperative preplanning (group 2). Biochemical status was assessed using two failure definitions: American Society for Therapeutic Radiology and Oncology (ASTRO) (three consecutive rises in prostate-specific antigen level) and Houston (prostate-specific antigen level>or=current nadir+2 ng/mL). Clinical disease-free survival and postimplantation dosimetry were also examined.

RESULTS

All disease control outcomes were superior for group 2. The 4-year ASTRO biochemical no evidence of disease rate was 80% for group 1 versus 94% for group 2. The 4-year Houston biochemical no evidence of disease rate was 82% for group 1 versus 96% for group 2. The 4-year clinical disease-free survival rate was 87% for group 1 versus 99% for group 2. Preplanning method (preoperative versus intraoperative) remained predictive of disease control outcomes in multivariate analyses with the covariates of pretreatment prostate-specific antigen level, Gleason score, clinical stage, and case sequence number (proxy for brachytherapist experience and "stage migration"). Dosimetric prostate coverage was superior for group 2. The mean percentage of the prescription dose delivered to 90% of the prostate volume (%D90) was 75% for group 1 versus 90% for group 2. A %D90>or=70% predicted for improved disease control; fewer group 1 than 2 patients met this dosimetric criterion (55% versus 87%).

DISCUSSION

Intraoperative preplanning yielded superior disease control outcomes in this analysis, likely due at least in part to improved dosimetric prostate coverage with this method. Although not mandatory for obtaining high prostate brachytherapy efficacy, intraoperative preplanning nevertheless may offer an excellent means of improving dosimetric prostate coverage and therefore disease control outcomes.