Login to Access Video or Poster Abstract: MP20-19
Sources of Funding: Supported by the NIH/NCI under Award Number P50CA09231 and NIH K24 CA160653

Introduction

Prostate-specific antigen doubling time (PSADT) is a useful marker for assessing disease aggressiveness at multiple stages of prostate cancer. However, in men with non-metastatic castration resistant prostate cancer (M0 CRPC), there are no commonly used PSADT cut-points for risk stratification. We examined whether PSADT correlates with metastases, all-cause mortality (ACM), and prostate cancer-specific mortality (PCSM) and identified PSADT cut-points that can be used clinically for risk stratification in men with M0 CRPC.

Methods

We collected data on 441 men with M0 CRPC in 2000-2015 at five Veterans Affairs hospitals. Cox models were used to test the association between log-transformed PSADT and development of metastasis, ACM, and PCSM. To identify cut-points, we categorized PSADT into groups of every 3 months (<3, 3-5.9, 6-8.9, 9-11.9, 12-14.9, 15-17.9, 18-20.9, 21-23.9, 24-119.9, 120) and then combined groups with similar hazard ratios. We tested the association between PSADT cut-points and each outcome using Cox models and compared survival using Kaplan-Meier estimates.

Results

Median age was 77 months (IQR: 70-83) and 160 (36%) men were black. Median PSADT was 13.3 months (IQR: 6.4-94.3) and median follow-up was 28.3 months (IQR: 14.7-49.1). As a continuous variable, PSADT was associated with metastases, ACM, and PCSM (HR 1.40-1.68, all p<0.001). We identified the PSADT cut-points <3, 3-8.9, 9-14.9, ≥15 months. As a categorical variable, PSADT was associated with metastases, ACM, and PCSM (all p<0.001). Men with a PSADT <3 months had a median 9 months to metastases, 16 months to PCSM, and 15 months to ACM. In contrast, men with a PSADT ≥15 months, had a median time to metastases of 50 months, 67 months to PCSM, and 46 months to ACM.

Conclusions

We found PSADT was a strong predictor of metastases, ACM, and PCSM in patients with M0 CRPC. As with patients at earlier disease stages, <3, 3-8.9, 9-14.9, and ≥15 are reasonable PSADT cut-points for risk stratification in men with M0 CRPC. These cut-points can be used for selecting high-risk men for clinical trials.

Funding

Supported by the NIH/NCI under Award Number P50CA09231 and NIH K24 CA160653