Combined androgen blockade achieved better oncological outcome in androgen deprivation therapy for prostate cancer: Analysis of community-based multi-institutional database across Japan using propensity score matching

Background: This study investigated how differences in the method of the first-line androgen deprivation therapy (ADT) affected the time to castration-resistant prostate cancer. Methods: The Japan Study Group of Prostate Cancer compiled a nationwide community-based database on prostate cancer patients who underwent ADT. That database included 13 774 patients who were started on ADT by surgical or medical castration alone (monotherapy group, 5395 cases) or ADT in combination with a nonsteroidal anti-androgen (combined androgen blockade (CAB) group, 8379 cases). We used logistic regression analysis with background factors as independent factors to calculate propensity scores in regard to selection of CAB. Next, for 8826 cases of propensity score-matched patients, we compared the survival rates in the two groups. Results: The CAB group showed a significantly better progression-free survival (PFS) rate (65.6% vs 59.6% at 5 years; median time to progression, 11.6 vs 7.1 years; hazard ratio in the CAB group: 0.78, with a 95% confidence interval of 0.72 to 0.84; P < 0.001). In subgroup analysis based on the background factors, the PFS rate was generally better in the CAB group in all risk subgroups except for those having significant risk factors. Conclusion: Propensity score matching analysis revealed the prolongation of PFS by CAB in prostate cancer patients without significant risk factors. It would possible to decide the type of the first-line ADT according to the prostate cancer risk.