Epidemiology, treatment patterns, and clinical outcomes in de novo oligometastatic hormone-sensitive prostate cancer.

92 Background: Oligometastatic hormone-sensitive prostate cancer (omHSPC) represents an advanced prostate cancer subset where metastasis-directed therapy (MDT) and prostate radiation therapy (RT) may improve clinical response and outcomes; however, there is a lack of published data on the epidemiology, clinical outcomes, and current treatment patterns. As such, we conducted a study to better characterize de novo omHSPC in the United States Veterans Affairs Health Care System (VA). Methods: This observational retrospective cohort study utilized chart abstracted data from the VA electronic medical record, as well as data from the VA Corporate Data Warehouse, a central repository of VA patient medical records. We randomly selected 400 men diagnosed with de novo mHSPC from 1/2015-12/2020. omHSPC was defined as up to 5 bone, lymph node, and/or visceral (excluding liver) metastases in total, identified by conventional imaging (bone scan, CT, and/or MRI). We estimated prevalence, described treatment patterns and used Kaplan-Meier methods to estimate overall survival (OS) and time to castration resistance from date of mHSPC diagnosis. The log rank test was used to compare differences in outcomes between omHSPC and non-omHSPC groups. Results: Of the 400 men with de novo mHSPC, 76 (19%) had omHSPC by conventional imaging. Men with omHSPC and non-omHSPC were similar in age, race, Gleason grade group, comorbidities, and metastatic site (bone and lymph node being most common). Men with non-omHSPC had a higher median PSA at mHSPC diagnosis (147.0) than omHSPC (38.3). The percentage of men on first-line (1L) novel hormonal therapy (NHT) use (most commonly abiraterone or enzalutamide) was similar between groups in the 1L setting (22.4% (omHSPC) vs 20.4% (non-omHSPC)), but the percentage of men on a 1L chemotherapy regimen was lower in omHSPC (5.3%) vs. non-omHSPC (13.6%). Overall, there was a higher percentage of men treated with MDT or prostate RT in omHSPC (13.2%) vs non-omHSPC cases (2.5%). Median OS in months (mos) was higher in men with omHSPC (55.3 mos, 95% CI 35.9-79.0) vs. non-omHSPC (25.9 mos, 95% CI 20.5-31.7, p=0.002). Median time to castration resistance was also longer in omHSPC (not reached [NR], 95% CI 42.2-NR) vs. non-omHSPC (29.3 mos, 95% CI 23.7-36.1, p=0.0014). Conclusions: Our study provides real-world insight into the prevalence, treatment patterns and clinical outcomes for omHSPC using a nationally representative VA sample. Approximately 1 in 5 men with de novo mHSPC were oligometastatic, and OS in men with omHSPC was more than double that of non-omHSPC. Although more men with omHSPC compared to non-omHSPC received potential curative therapy, the percentage was still relatively low. Future studies are warranted as several clinical trials are investigating the potential for prolonged responses with aggressive, multimodal therapy inclusive of systemic and local therapies.