Survival and Economic Impact of Rapid Prostate-Specific Antigen Doubling Time in Patients With Nonmetastatic Castration-Resistant Prostate Cancer.

Abstract

In patients with nonmetastatic castration-resistant prostate cancer (nmCRPC), prostate-specific antigen doubling time (PSADT) is associated with risk of metastasis and survival. This study evaluated the association of PSADT with clinical and economic outcomes in a real-world setting among patients with nmCRPC not receiving novel hormonal therapy (NHT), using 2-month PSADT thresholds. We retrospectively identified Veterans Health Administration patients with nonmetastatic prostate cancer and ≥2 PSA increases after medical/surgical castration (2012-2016). The third measurement was the index (CRPC) date. Patients with ≥3 postindex PSA measurements, including index, were followed until death or ≥12 months until disenrollment, study end, or death, and grouped into 2-month cohorts based on postindex PSADT. Cox regression models assessed association between PSADT, time to metastasis, and death. Healthcare resource utilization and costs were evaluated. Among 2800 evaluable patients, median follow-up was 30 months and median PSADT was 17 months. Relative to the reference cohort (PSADT >12 months), all cohorts had significantly higher metastasis risk. PSADT ≤10-month cohorts had significantly greater mortality risk than the reference; hazard ratios (95% confidence intervals) ranged from 12.3 (9.2, 16.4) in the PSADT ≤2-month cohort to 1.3 (0.9, 2.0) in the >10 to ≤12-month cohort. Total costs were significantly higher for cohorts up to and including the PSADT >8 to ≤10-month cohort, than for the reference cohort. Mean per patient per month all-cause medical plus pharmacy costs were $6623, $4768, and $4049 in the PSADT ≤2-month, >2 to ≤4-month cohort, and >4 to ≤6-month cohorts, respectively, versus $1911 in the PSADT >12-month cohort (P <0.05). Most patients with nmCRPC have PSADT >12 months and a long natural history. For those with shorter PSADT, the risk of metastasis, death, and costs increased. These data can help select patients for NHT and conversely those who can safely delay NHT for nmCRPC.