Real-world practice patterns and predictors of continuous versus intermittent androgen deprivation therapy use for prostate cancer in older men

Purpose — Phase-III RCT evidence suggests intermittent ADT (IADT) is not significantly inferior to continuous ADT for prostate cancer (PC) patients. However, clinical practice and guidelines differ in their recommendations. We evaluate real-world utilization and practice patterns of IADT.

Materials and Methods — Ontario men ≥65 years with PC who initiated ADT for ≥3 months were identified (1997-2017). Lapses in ADT ≥6 months (initial gap) and ≥3 months (subsequent gaps) were used to classify IADT. Neoadjuvant/adjuvant therapy was excluded. Disease stage adjustment was completed for patients with likely metastatic disease based on de-novo presentation with ADT. Patient and physician predictors of IADT were analyzed using multivariable logistic regression.

Results — 8,544 patients were identified with 1,715 having previously received local therapy. Amongst all patients, 16.4% received IADT. This ranged from 11.4-24.8% across health-planning regions, and increased to 26.6% in those with previous local therapy. Mean follow-up was 8.3 years. Patients with prior local therapy [OR1.85 (95% confidence interval 1.59-2.17), p <0.001] and those in the highest income quintile [OR1.32 (1.08-1.60), p=0.005] had increased odds of receiving IADT. Radiation oncologists were more likely to use IADT than urologists [OR1.99 (1.59-2.50), p <0.001], as were physicians with more experience [≥10 years in practice: OR1.44 (1.11-1.88), p=0.007]. In specialty-stratified analyses, case volume was significantly associated with IADT for radiation oncologists [highest quartile: OR1.73 (1.14-2.62), p=0.009].

Conclusion — IADT remains underutilized for PC patients ≥65 years with only 1-in-4 to 1-in-6 eligible patients receiving this form of care. Clinical, sociodemographic, and physician characteristics play an important role in treatment selection.