Clinical characteristics and outcomes of veterans with metastatic hormone-sensitive prostate cancer (mHSPC) based on volume of disease and site of metastases.

e17083 Background: Metastatic hormone-sensitive prostate cancer (mHSPC) is categorized by volume of disease and high tumor volume is associated with worse outcomes. Assessment of volume of disease and site of metastases at diagnosis may help risk stratify patients with mHSPC. This study describes patient characteristics and survival in U.S. veterans treated for mHSPC. Methods: Veterans were identified with initial diagnosis of SEER stage ‘distant’ prostate cancer. All veterans had androgen deprivation therapy (ADT) initiated within 4 months of diagnosis and followed until September 2023. Veterans treated with ADT alone during 2018, ADT+docetaxel (DOC) from 7/2016-6/2021 or androgen receptor pathway inhibitors (ARPIs) abiraterone, enzalutamide, apalutamide, and darolutamide from 7/2017-6/2021 were included if initiated within 4 months after ADT. Veterans were categorized as high or low volume of disease by chart review. If patients had more than one site of metastasis, they were categorized as follows: any liver, any lung, any high volume bone. Age, PSA, and body mass index (BMI) were collected at diagnosis and compared by ANOVA or Kruskal-Wallis with Bonferroni correction for multiple comparisons. Results: 1520 veterans were identified with 886 high volume bone metastases, 154 lung metastases, 70 liver metastases, and 410 low volume patients. Mean age of patients was 72.3 years (SD 0.4) with median PSA of 103.2 ng/mL and mean BMI of 27.4. There was no difference in mean age between high volume and low volume (72.3 vs. 72.5 years, p=0.28), however median PSA was higher in high volume (152.0 vs. 48.8 ng/mL, p<0.001) and median BMI was lower in high volume (26.5 vs. 27.5, p=0.002). High volume metastasis was associated with shorter survival (31.2 vs. 56.3 months, p<0.001). For site of metastases, there was no difference in age between location (p=0.365), PSA was higher in liver, lung, and high volume bone compared to low volume while for BMI, only liver metastasis was associated with significantly lower BMI. Liver metastasis was associated with shorter survival compared to low volume, high volume bone, and lung metastasis (all p<0.001 by log-rank). Conclusions: High volume disease and liver metastases were associated with shorter survival in veterans with mHSPC. Presence of liver metastasis was independently associated with decreased overall survival compared to high volume bone or lung metastases. Volume of disease and location of metastases may provide information for prognostication in mHSPC. [Table: see text]