Intermittent maximal androgen blockade in patients with metastatic prostate cancer: an EORTC feasibility study

In preparation of an intercontinental Phase III trial comparing continuous maximal androgen blockade (MAB) to intermittent androgen suppression (IAS) in untreated metastatic prostate cancer, a feasibility study on IAS was accomplished.

107 patients (median follow-up 92 weeks) were treated with MAB until a PSA nadir was reached. Nadir was defined as PSA below 20 ng/ml corresponding to PSA reduction by at least 80% of baseline value. Criteria for restarting treatment was PSA >20 ng/ml and PSA > nadir + 50%. Trials aim was to assess the likelihood that 80% of patients would reach a first nadir and that 80% of these would also reach a second nadir.

51.4% of patients had some degree of pain at entry, 27.1% had >15 hot spots, 23.7% demonstrated obstruction. Only 17.8% had normal potency, 56.1% were totally impotent. One to seven cycles of treatment were given. 76.6% of patients reached a 1st nadir after a median of 19 weeks of treatment, 84.1% of these started the 2nd cycle and 71% of them reached a 2nd nadir after a median of 13.6 weeks. Median time off-treatment was 14.3 and 16.0 weeks corresponding to 38.4% and 48.5% of the duration of each cycle. A similar proportion of patients was reported to be potent during follow-up compared to baseline. 32.7% of patients died during follow-up, 82.9% of prostate cancer.

Around 75% of the patients achieved a nadir at each cycle. The concept of IAS seems to be feasible and warrants further investigation.