20Gy versus 44Gy supplemental beam radiation with Pd-103 prostate brachytherapy: Preliminary biochemical outcomes from a prospective randomized multi-center trial.

摘要

BACKGROUND AND PURPOSE: 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. PATIENTS AND 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 10-20ng/ml, were treated on a randomized protocol comparing 44 versus 20Gy pre-implant supplemental beam radiation, combined with Pd-103, 90 versus 115Gy, respectively (NIST-1999). Freedom from biochemical failure was defined as a serum PSA0.5ng/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 20Gy and nine treated with 44Gy. There were no clinically evident local failures. The actuarial biochemical freedom-from-failure rate at 3 years was 83% for 20Gy patients versus 88% for 44Gy patients (P=0.64). For 112 patients with a pre-treatment PSA<10ng/ml, the 3-year freedom from progression was 84% in patients receiving 20Gy beam radiation versus 94% in those who received 44Gy beam (P=0.16). For 47 patients with a pre-treatment PSA>10ng/ml, the 3-year freedom from progression was 82% in patients receiving 20Gy beam radiation versus 72% in those who received 44Gy beam (P=0.38). CONCLUSIONS: The randomized data presented here suggests that the likelihood of biochemical cure is similar with standard (44Gy) or lower dose (20Gy) supplemental beam radiation. Since the biological effect of 20Gy 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 0Gy supplemental beam radiation.