Survival of de novo metastatic hormone sensitive prostate cancer in US Veterans based on treatment and PSA at diagnosis.

Abstract

e17091 Background: Combinations of androgen deprivation therapy (ADT) plus docetaxel (DOC) or androgen signaling agents (ASIs) (i.e. abiraterone, enzalutamide) improve survival in de novo metastatic hormone sensitive prostate cancer (mHSPC). In several trials, the benefit of combination therapy is greatest in patients with a high volume of disease. We sought to study the treatment and survival of US of veterans with mHSPC and stratify by PSA level at diagnosis during a time when different types of combination therapy was available. Methods: Veterans from 2018-2021 were identified with a pathologic diagnosis of prostate cancer with SEER stage ‘distant’. All veterans had ADT initiated within 1 month prior and 4 months after diagnosis. Combination therapy was determined if DOC or an ASI was initiated from 1 month prior to 4 months after ADT. Highest PSA level within 3 months of diagnosis was collected and patients with a PSA of ≥100ng/mL were included in PSA≥100. To avoid immortal time bias, all veterans had to survive 4 months after biopsy to be included. Baseline differences were compared using ANOVA and log-rank testing was used for time to event analyses. Results: 2,227 patients with de novo mHSPC were identified with mean age of 74.0 years (yrs), and 575 (25.8%) identified as Black race. From 2018 to 2021, ADT alone was used in 1,157 (52.0%) of veterans, DOC in 189 (8.4%) and ASIs in 881 (39.6%). Veterans treated with DOC were significantly younger (median 67.7 yrs, p < 0.001) compared to veterans treated with ASIs (72.9 yrs) or ADT alone (75.8 yrs). Veterans treated with combination therapies had longer median OS of 40.9 months (mos) compared to 32.9 mos for ADT alone (p < 0.001) with no difference within the combination treatment groups (p = 0.63). There was a trend for veterans with PSA≥100 to receive combination therapy (50.0% vs. 46.0%, p = 0.058). For 1,071 veterans with PSA≥100, median OS of veterans treated with combination therapy (n = 536, 37.4 mos) was longer than ADT alone (n = 535, 27.5 mos, p < 0.001). There was no differences in DOC combination treatment (n = 100, 37.9 mos) and ASI (n = 436, 36.6 mos) treatment groups (p = 0.37). Veterans with PSA≥100 had shorter OS compared to PSA < 100 (31.2 vs. 42.5 mos, p < 0.001). Conclusions: In veterans with de novo mHSPC, initial combination therapy was associated with longer survival than ADT alone. There were no differences in survival between DOC and ASI combinations observed in the entire population nor in veterans with PSA≥100. Further studies including tumor genetics or response to treatment may help guide treatment in mHSPC. [Table: see text]