Continuous androgen deprivation therapy remains the standard of care for newly diagnosed hormone-sensitive metastatic prostate cancer, according to the phase III Southwest Oncology Group (SWOG) 9346 intergroup trial presented at this year’s ASCO Plenary Session.¹

Study Rationale

The large international trial of 3,040 men failed to show noninferiority of intermittent androgen deprivation vs continuous androgen deprivation. Intermittent treatment has been proposed, and frequently employed, as possibly a more tolerable and equally effective approach in this patient population. The SWOG trial set out to test this assumption.

The subjects had newly diagnosed metastatic disease and prostate-specific antigen (PSA) levels ≥ 5 ng/mL, for which they received hormone therapy (goserelin [Zoladex] and bicalutamide) for 7 months. Patients whose PSA fell to ≤ 4 ng/mL (ie, responders who were therefore particularly hormone-sensitive) were randomly assigned to either intermittent therapy—stopping treatment at that point until a rise in PSA was observed or symptoms appeared—or to continuous therapy.

Major Data

At a median follow-up of 9.2 years, median overall survival was 5.1 years with intermittent androgen deprivation and 5.8 years with continuous therapy (HR = 1.09; 95% CI = 0.95–1.24).

The study design specified that survival with intermittent androgen deprivation would be noninferior to continuous therapy if the upper 95% confidence boundary for the hazard ratio did not reach or include 1.2. However, this criterion was not met. The hazard ratio of 1.09 favored continuous therapy (9% more deaths occurred on the intermittent arm), and the upper boundary of the 95% confidence interval was 1.24, so the conclusion was that the two treatments could not be called equivalent. ■

Reference

1. Hussain M, Tangen CM, Higano CS, et al: Intermittent versus continuous androgen deprivation in hormone sensitive metastatic prostate cancer patients: Results of S9346 (INT-0162), an international phase III trial. 2012 ASCO Annual Meeting. Abstract 4. Presented June 3, 2012.