Conversion to monotherapy with luteinizing-hormone releasing hormone agonist or orchiectomy after reaching PSA nadir following maximal androgen blockade is able to prolong progression-free survival in patients with metastatic prostate cancer: A propensity score matching analysis

The present study evaluated androgen deprivation methods to determine the approach that most improves the progression-free survival (PFS) of patients with metastatic prostate cancer. Patients had received continuous maximal androgen blockade (MAB) or monotherapy [luteinizing-hormone releasing hormone (LHRH) agonist or orchiectomy] following the reaching of the prostate specific antigen (PSA) nadir. The medical records of 293 patients who received MAB following a diagnosis of metastatic prostate cancer were retrospectively reviewed. Following attainment of the PSA nadir and treatment with MAB, patients were maintained on continuous MAB (group CMAB) or converted to monotherapy (group MONO). Disease progression, defined as progression to castration-resistant prostate cancer, was evaluated and compared between the treatment modalities. PFS was compared between patients who received CMAB vs. MONO using 2:1 (102:53) propensity score matching; the basic clinicopathological characteristics (age, Gleason score, PSA and extent of bone metastasis) were similar between the groups. Disease progression was observed in 70.9% of all patients, with a median treatment period of 22.7 months. The median PFS time was 19.5 months in the CMAB group and 28.8 months in the MONO group (P=0.008). Kaplan-Meier analysis demonstrated that PFS was significantly associated with the type of maintenance androgen deprivation therapy (ADT; log rank <0.005). Multivariate analysis revealed that the type of maintenance ADT and the pretreatment extent of bone metastasis were independent predictors of prolonged PFS. In this propensity score matched-analysis, conversion to monotherapy with a LHRH agonist or orchiectomy following attainment of the PSA nadir with initial MAB, prolonged the PFS, suggesting that monotherapy maintenance following initial MAB may benefit patients by reducing side effects without decreasing treatment efficacy.