Association of basophil to lymphocyte ratio (BLR) with clinical outcomes in metastatic hormone sensitive prostate cancer.

e17049 Background: There is limited biomarker data available for metastatic hormone sensitive prostate cancer (mHSPC). Inflammatory markers found on routine clinical lab data, including leukocyte to lymphocyte ratios calculated from complete blood counts (CBC), is associated with clinical outcomes (CO) in different malignancies. We investigated the association between basophil-to-lymphocyte ratio (BLR) and CO in a racially diverse patient population with mHSPC. Methods: We performed a retrospective multicenter review from Winship Cancer Institute at Emory University and Georgia Cancer Center for Excellence at Grady Memorial Hospital (2014 – 2020). Demographics, disease characteristics, and laboratory data were collected at the start of upfront therapy with either docetaxel (DOC) or abiraterone (ABI). Overall survival (OS) and progression-free survival (PFS) were used to measure CO. Results: Included were 165 patients with mHSPC with a median follow-up time of 22.6 months. 89 (53.9%) were Black and 76 (46.1%) were Non-Black (White, Asian, or Hispanic). 106 (63%) had Gleason scores of 8-10 and 105 (63.6%) were classified as high-volume disease (per CHAARTED trial criteria). 92 (55.8%) received DOC and 73 (44.2%) received ABI. Worse CO were associated with high BLR at an optimal cut of 0.0265 (range 0 – 0.81 , mean of 0.03, standard deviation 0.09). Elevated BLR is associated with decreased OS (HR 3.51, 1.79 – 6.91, p <0.001) and PFS (HR 1.85, 1.14 – 3.00, p 0.013) in multivariable analyses (MVA). High BLR and low BLR groups were similar except for age as a continuous variable, which was associated with high BLR. Otherwise, there were no significant difference for all reported clinical characteristics, including drug (DOC vs ABI), race (Black vs Non-Black), Gleason, disease volume (per CHARRTED criteria), ECOG, or BMI. Conclusions: In mHSPC, high baseline BLR is associated with worse OS and PFS. Our results are the first to identify that BLR is associated with CO in mHSPC. Further study is needed to validate BLR as a potential biomarker.[Table: see text]