Login to Access Video or Poster Abstract: MP33-08
Sources of Funding: none

Introduction

Prostate specific antigen (PSA) in midlife predicts increased risk of lethal prostate cancer (CaP). However, many men do not initiate CaP screening until later in life. Our aim was to determine if baseline PSA predicts lethal or metastatic CaP in an observational study of a US cohort.

Methods

Subjects were identified from the Prostate Lung Ovarian and Cancer (PLCO) trial. Men 60 years or older with a prior PSA in the control arm were excluded. Men were categorized by baseline PSA (at or below the 50th percentile, above the 50th percentile, 75th percentile and 90th percentile). Cox hazard ratios were used to compare subsequent risk of metastatic and lethal CaP, controlling for age, race, marital status, level of education, income, body mass index, and smoking.

Results

We identified 10,855 men 60 years or older without PSA screening prior to enrollment in the PLCO screening arm. Median age at first PSA was 65 (interquartile range 62-68). Median baseline PSA was 0.7, 1.6, 3.5 and 5.8 in those at or below the 50th percentile, above the 50th percentile, 75th percentile and 90th percentile, respectively. In this cohort, there were 39 deaths attributable to CaP and 147 cases of metastatic CaP. The rate of metastatic CaP and lethal CaP increased with increasing baseline PSA. Those below the 50th percentile had a 0.18% and 0.26% incidence of lethal and metastatic CaP respectively. Comparatively, those in the 90th percentile reported a 3.1% and 4.7% incidence of lethal and metastatic CaP respectively (p<0.001 between 50th and 90th percentiles). On Cox regression, higher percentile baseline PSA was associated with a significantly higher risk of metastatic and lethal prostate cancer [highest vs. lower percentile group: Hazard Ratio (HR)=27.8 (95% Confidence Interval (CI)14.9-52.1); HR=16.3, (95% CI 7.6-35) p<0.001, respectively].

Conclusions

Baseline PSA testing for men aged 60 and over is strongly associated with metastatic CaP at diagnosis and lethal CaP. Men with low baseline PSA, very infrequently develop lethal CaP. These findings should help guide the frequency and intensity of individualized PSA screening

Funding

none