The effect of isotope selection on the prostate-specific antigen response in patients treated with permanent prostate brachytherapy.
OBJECTIVE
To assess the difference in prostate-specific antigen (PSA) response kinetics in patients undergoing either (125)I or (103)Pd permanent prostate brachytherapy (PPB).


METHODS
Between 1997 and 1999, 333 patients underwent PPB as monotherapy. Forty-eight patients received a (125)I implant, and 285 received a (103)Pd implant. Biochemical relapse-free survival was defined by the Kattan modification of the American Society for Therapeutic Radiology and Oncology consensus, based on three PSA increases. In addition, the time to reach a PSA threshold of <or=1.0 ng/ml was noted. Log-rank testing was performed, and multivariate analysis was used to evaluate those variables associated with biochemical freedom from recurrence.


RESULTS
With a mean 36-month follow-up, the actuarial biochemical relapse-free survival at 4 years was 86.8%. No significant difference in biochemical relapse-free survival was noted between patients treated with (125)I and (103)Pd (p=0.417). Multivariate analysis failed to identify isotope as an independent variable to predict for biochemical relapse-free survival. The mean time for patients treated with (103)Pd to reach the threshold PSA value was 10.2 weeks, whereas it was 22 weeks for (125)I (p=0.014). When the median time to reach the PSA threshold of <or=1.0 ng/ml was used to calculate the percentage of delivered dose for each isotope relative to the prescribed dose, there was no significant difference noted between (125)I (84%) and (103)Pd (94%) (p=0.86).


CONCLUSIONS
Isotope selection does not appear to influence biochemical relapse-free survival in patients treated with monotherapy PPB. There was a significant difference (p=0.014) in time to reach a PSA threshold of <or=1.0 ng/ml noted between (125)I and (103)Pd. However, the percentage of delivered dose relative to the time to reach the threshold was the same between (125)I and (103)Pd. This information is important for during patients their post-PPB period.
Potters
Louis
L
Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center at Mercy Medical Center, Rockville Centre, NY 11570, USA. pottersl@mskcc.org
Huang
David
D
Fearn
Paul
P
Kattan
Michael W
MW
D000230:Adenocarcinoma / Q000401:mortality / Q000532:radiotherapy*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000528:radiation effects*; D001918:Brachytherapy; D018572:Disease-Free Survival; D005500:Follow-Up Studies; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009364:Neoplasm Recurrence, Local / Q000401:mortality / Q000532:radiotherapy; D009367:Neoplasm Staging; D009518:New York; D010165:Palladium / Q000627:therapeutic use; D011237:Predictive Value of Tests; D017430:Prostate-Specific Antigen / Q000528:radiation effects*; D011471:Prostatic Neoplasms / Q000401:mortality / Q000532:radiotherapy*; D011868:Radioisotopes / Q000627:therapeutic use*; D013997:Time Factors; D016896:Treatment Outcome
D014408:Biomarkers, Tumor; D007457:Iodine Radioisotopes; D011868:Radioisotopes; D010165:Palladium; D017430:Prostate-Specific Antigen