Large institutional variations in androgen deprivation therapy utilization with definitive radiotherapy in a population-based cohort of men with intermediate- and high-risk prostate cancer

Abstract

OBJECTIVE: To evaluate the pattern of androgen deprivation therapy (ADT) utilization with definitive radiotherapy (RT) in men with prostate cancer (CaP) in a population-based study in Australia PATIENTS AND METHODS: This is a prospective cohort of men with intermediate and high-risk CaP captured in the population-based Prostate Cancer Outcome Registry Victoria (PCOR-Vic) treated with definitive prostate RT between January 2010 and December 2015. The primary outcome of interest is ADT utilization. Chi-squared test for trend was used to evaluate temporal trend in ADT utilization over the study period. Multivariate logistic regressions were used to evaluate the effect of patient-, tumour-, treatment-factors, and treatment institutions (public/ private and metropolitan/ regional) on the likelihood of ADT utilization. RESULTS: 1806 men were included in the study - 199 (11%) favourable NCCN intermediate risk (i.e. only one intermediate risk feature, primary Gleason grade 3, and <50% biopsy core involved), 687 (38%) unfavourable NCCN intermediate risk, and 920 (51%) high risk. Of these, 1155 (64%) had ADT with RT. NCCN high-risk CaP patients (84%) were more likely to have ADT compared to favourable NCCN intermediate-risk (32%) and unfavourable NCCN intermediate-risk (46%) patients (P<0.001). Patients treated in public institutions (66% vs. 47% in private, P<0.001) and regional centres (78% vs. 59% in metropolitan, P<0.001) were more likely to have ADT. There is trend towards increased ADT utilization from 50% in 2010 to 64% in 2015 (P<0.001). In multivariate analyses (adjusting for age, tumour factors, year of treatment and use of brachytherapy boost), treatment institutions (public and regional) remained independently associated with increased likelihood of ADT utilization. Intermediate risk patient treated in regional and public institutions were 2.7 times (95%CI=1.9-3.9, P<0.001) and 2.8 times (95%CI=1.4-5.3, P=0.002) more likely to have ADT with RT, whereas high risk patients treated in regional and public institutions were 3.1 times (95%CI=1.7-5.7, P<0.001) and 3.0 times (95%CI=1.7-5.4, P<0.001) more likely to have ADT with RT CONCLUSION: This is the largest Australasian contemporary series reporting on the pattern of ADT utilization with definitive prostate RT. While there is increasing trend in ADT utilization over time, ADT still appears under-utilized in certain groups of patients who may benefit from ADT, with approximately 1-in-5 high risk, and 1-in-2 unfavourable intermediate risk patients not receiving ADT with RT. There is notable variation in ADT utilization between public/ private and metropolitan/ regional institutions. This article is protected by copyright. All rights reserved.