Understanding heterogeneity of treatment effect in prostate cancer

Purpose of review In the era of personalized medicine, oncologists seek to tailor treatments for their patients based on indicators of differential response to treatment. We first provide a conceptual explanation of heterogeneity of treatment effect using prostate cancer as a case study and review studies that test whether Gleason score has a role in modifying the effectiveness of androgen deprivation therapy in men newly diagnosed with metastatic prostate cancer. Recent findings Depending on the study design, setting, and population, the median time to develop castration-resistant prostate cancer ranges from 12 to 23 months among men with M1 disease on androgen deprivation therapy, and the median time from diagnosis to mortality in such patients ranges from 23 to 37 months. Patients with higher Gleason scores have a significantly shorter time to developing castration-resistant prostate cancer compared with patients with lower Gleason scores. However, data suggest that Gleason score does not have a role in modifying the survival benefit associated with androgen deprivation therapy. Summary Androgen deprivation therapy has heterogeneous effects in men with metastatic prostate cancer related to the time of developing castration resistance. However, survival benefit from androgen deprivation therapy does not appear to depend on Gleason score.