Long enough.

Might mean forever if talking about androgen deprivation therapy (ADT) for very high risk prostate cancer. This meta-analysis examined the effects of length of ADT on survival among men with high Gleason (≥8) prostate cancer. It included almost 1K patients with high Gleason scores enrolled across 6 clinical trials assessing various durations (including no) ADT in combo with definitive radiation. For patients with Gleason 8 disease, long-term ADT of at least 28 months conferred the lowest hazard ratio for death (0.43). For patients with Gleason 9-10 disease, lifelong ADT was the winning regimen with a hazard ratio of  0.48. TBL: As suggested, more ADT probably means more relative prostate cancer control...which inevitably confers the most benefit in those with the highest risk disease. | Kishan, JAMA Oncol 2018