Intermittent androgen castration: a biological reality during intermittent treatment in metastatic prostate cancer?

To assess the effects of intermittent maximal androgen blockade (IMAB) on testosterone (T) levels during on- and off-treatment periods.

A total of 51 patients with metastatic prostate cancer underwent a 6-months period of continuous maximal androgen blockade (MAB) consisting of leuprorelin (3.75 mg at monthly intervals) plus flutamide (250 mg t.i.d.) followed by IMAB. During each cycle, the cut-off prostate-specific antigen (PSA) levels to stop and resume treatment were 4 and 10 ng/ml, respectively. IMAB continued until progression under treatment occurred. Monthly PSA and T measurements were performed in central laboratories.

From the 51 patients included (mean age 67.6 years), 27, 16, 12, 8 and 5 underwent a second, third, fourth, fifth and sixth cycle, respectively (mean follow up: 17 months). Before treatment, 4 patients had a T lower than normal laboratory value but these recovered all to a normal T value at the end of the first cycle. During the 6 cycles, only 8 patients did not recover a normal T at least once during the off-treatment periods (OTP). The mean T values at the end of each OTP did not change during these 6 cycles (Anova test, p=0.621) with a mean stable recovery delay of 32-43 days (Anova test, p=0.722).

IMAB protocol with an initial 6-month treatment period can result in an intermittent castration with the recovery of normal T levels in most patients during six consecutive cycles of treatment.