Geographic variation in systemic therapy in men age 66 years and older with de novo metastatic castration-sensitive prostate cancer: A population-based study in a single payer health-system.

50 Background: Significant developments in the standard of care for patients with de novo metastatic castration-sensitive prostate cancer (mCSPC) have been reported over the past decade. Treatment intensification with systemic therapies in addition to androgen deprivation therapy (ADT) alone is guideline recommended for most patients. We studied the geographic variation in the use of systemic therapy for de novo mCSPC in Ontario, Canada, a single-payer health system. Methods: We performed a population-based study of men aged 66 years and older diagnosed with de novo mCSPC between 2014-2019. We linked population-based healthcare databases, as administered at the level of Local Health Integration Networks (LHINs) in Ontario, to examine treatment patterns following diagnosis of de novo mCSPC. We categorized initial mCSPC treatments as those begun within 60 days preceding and 6 months following diagnosis and examined the proportion of patients receiving LHRH alone, first generation anti-androgen (AA) alone, combined androgen blockade (CAB; LHRH + 1st gen AA), ADT + abiraterone acetate + prednisone (AAP), and, ADT + docetaxel (D). In aggregate, we considered LHRH alone, AA alone and CAB as “standard ADT”, and ADT + AAP and ADT + D as “ADT-plus”. Multinomial logistic regression analyses were used to examine the association between receiving systemic treatment intensification (“ADT-plus”) or no prostate cancer pharmacotherapy relative to ADT across geographic regions, while adjusting for baseline patient and disease characteristics. Results: We identified 3,556 men over 66 with de novo mCSPC. Overall, 2794 (78.6%) received standard ADT, 311 (8.7%) did not receive prostate cancer-directed pharmacotherapy, and 451 patients (12.7%) of patients received “ADT-plus”. Utilization of AAP increased from 0.5% to 3% following the LATITUDE data release in 2017, while D decreased from 12% to 10%. There was significant variation in treatment strategies between geographic regions in use of “ADT-plus” ranging from 7 to 20% (p < 0.0001), a difference which persisted after accounting for patient demographics, comorbidity, rurality, and disease characteristics (p = 0.036). Conclusions: Despite proven survival benefits in randomized controlled trials, intensified treatment with docetaxel or abiraterone in addition to ADT was infrequently utilized in this population-based study of men age 66 years and over with mCSPC.

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