Purpose: The object of this study was to evaluate the duration of response to intermittent androgen deprivation (IAD) in patients with nonmetastatic recurrent or localized prostate cancer.
Patients and methods: One hundred ten patients received IAD from February 1992 to February 2005. One hundred three patients were treated after failure of primary radiation therapy and/or prostatectomy, with the remaining 7 patients treated primarily with IAD. The median duration of treatment cycle was 6 months. Patients were considered resistant to hormone therapy if the prostate-specific antigen (PSA) level increased, with castrate levels of testosterone. At the time of initial diagnosis, the median Gleason score was 7 (range, 4-9), and tumor stages were as follows: T1/T2 (n = 73), T3 and T4 N1 (n = 34), and other (n = 3). The median PSA at the initiation of IAD was 8.25 ng/mL.
Results: The median follow-up after beginning IAD was 45.5 months. Patients received a median of 2 cycles (range, 1-9 cycles). Ninety-four of 110 patients (85.5%) remained responsive to IAD. Sixteen patients (14.5%) progressed to become refractory to primary hormone treatment. Patients with a higher tumor stage (T3 and T4) were significantly more likely to develop resistance. The median time to become refractory to hormone therapy was 47.9 months (range, 9.4-93.4 months). Five patients were put on secondary continuous hormone treatment, and 3 of them developed resistance at a median of 9 months. One patient was put on a secondary IAD and was still responding at the last follow-up.
Conclusion: With 85.5% of the original patient population still responding to the primary hormone therapy at 45.5 months of follow-up, IAD appears to be a viable option for patients with biochemical failure after local radiation therapy. A pattern of shortening time between cycles and an increasing nadir PSA level with each successive cycle is consistent with the gradual development of hormone resistance.