Purpose:
Prostate cancer patients treated with high dose rate brachytherapy and external beam radiation therapy were stratified by risk group for analysis to determine whether androgen deprivation therapy (ADT) affected outcome.
Methods:
From 1991 through1998, 411 patients were treated with 4 fractions of 5.5 to 6.0 Gy high dose rate brachytherapy and a total of 36.0 to 39.6 Gy external beam radiation therapy (dose escalation over time). The dataset was prospective. Administration of ADT was not randomized, but it was the primary study variable. During this period, ADT was administered across all risk groups for various indications. It did not necessarily reflect advanced disease or large prostate size. There were 200 patients in the “ADT Group” (20% low, 48% intermediate, and 32% high risk) and 211 in the “No ADT Group” (33% low, 44% intermediate, 23% high risk). The median follow-up was 6.4 years. Cases were grouped according to low, intermediate, and high risk groups to reduce the effects of unrecognized selection bias for or against the ADT group. The prostate specific antigen (PSA) nadir plus 2.0 ng/ml (nadir + 2) was used as the biochemical control end point. Local control, PSA progression-free survival, distant metastasis free survival, and cause-specific survival were compared.
Results:
The 10 year PSA-PFS (nadir + 2) for all 411 patients was 81%. The results stratified by risk group were: low 92%, intermediate 87%, and high 63%. The low and intermediate risk groups were not statistically different from one another but they were both significantly better than the high risk group. ADT versus No ADT 10-year survival showed no significant differences for any outcome variable: PSA-PFS (83% vs. 81% ns), local control (97% vs. 99%), distant metastasis free survival (94% vs. 97%), and cause-specific survival (97% vs. 97%). A subset analysis of PSA-PFS (nadir + 2) stratified by risk group revealed no difference between the ADT and No ADT groups.
Conclusions:
high dose rate brachytherapy and external beam radiation therapy resulted in high rates of local control, PSA progression-free survival, distant metastasis free survival, and cause-specific survival in all risk groups. Improved outcome from the use of androgen deprivation was not observed.
