20 Gy versus 44 Gy supplemental beam radiation with Pd-103 prostate brachytherapy: preliminary biochemical outcomes from a prospective randomized multi-center trial.
OBJECTIVE
While favorable results are achieved with combined modality irradiation, there has never been a rigorous study of the need for supplemental beam. The study reported here compares clinical outcomes with substantially different external beam radiation doses. Similar to classic randomized Wilm's tumor studies from the 1980s, the intention of the trial design was to decrementally test the need for beam radiation.


METHODS
As of June 2000, 165 of a planned 600 patients with 1997 AJC clinical stage T1c-T2a prostatic carcinoma, Gleason grade 7-10 and/or PSA 10-20 ng/ml, were treated on a randomized protocol comparing 44 versus 20 Gy pre-implant supplemental beam radiation, combined with Pd-103, 90 versus 115 Gy, respectively (NIST-1999). Freedom from biochemical failure was defined as a serum PSA</=0.5 ng/ml at last follow-up. Patients were censored at last follow-up if their serum PSA was still decreasing. Patients whose serum PSA nadired at a value >0.5 ng/ml were scored as failures at the time at which their PSA nadired. The follow-up period for non-failing patients ranged from 0.5 to 4.9 years (median: 2.9 years). Accrual of 566 patients was achieved in October 2004. The study was closed at that time because of slowing accrual, due in part to the findings reported here.


RESULTS
The overall actuarial freedom from biochemical progression at 3 years is 85%, with 59 patients followed beyond 3 years. A total of 21 patients have developed biochemical failure, 12 treated with 20 Gy and nine treated with 44 Gy. There were no clinically evident local failures. The actuarial biochemical freedom-from-failure rate at 3 years was 83% for 20 Gy patients versus 88% for 44 Gy patients (P=0.64). For 112 patients with a pre-treatment PSA<10 ng/ml, the 3-year freedom from progression was 84% in patients receiving 20 Gy beam radiation versus 94% in those who received 44 Gy beam (P=0.16). For 47 patients with a pre-treatment PSA>10 ng/ml, the 3-year freedom from progression was 82% in patients receiving 20 Gy beam radiation versus 72% in those who received 44 Gy beam (P=0.38).


CONCLUSIONS
The randomized data presented here suggests that the likelihood of biochemical cure is similar with standard (44 Gy) or lower dose (20 Gy) supplemental beam radiation. Since the biological effect of 20 Gy external beam radiation is likely to be small, we interpret these preliminary results to suggest that supplemental beam radiation is unnecessary, in the setting of a high degree of prostate coverage by the brachytherapy prescription dose. With closure of this study, we have begun treating intermediate and high risk patients on a prospective randomized comparison of Pd-103 with 20 versus 0 Gy supplemental beam radiation.
Wallner
Kent
K
Department of Veterans Affairs, Radiation Oncology, Puget Sound Health Care System, Seattle, WA 98108-1597, USA. kentwallner@med.va.gov
Merrick
Gregory
G
True
Lawrence
L
Sherertz
Tracey
T
Sutlief
Steven
S
Cavanagh
William
W
Butler
Wayne
W
D000368:Aged; D001918:Brachytherapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D010165:Palladium / Q000627:therapeutic use*; D011446:Prospective Studies; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood / Q000532:radiotherapy*; D011868:Radioisotopes / Q000627:therapeutic use*; D011879:Radiotherapy Dosage
D011868:Radioisotopes; D010165:Palladium; D017430:Prostate-Specific Antigen