The use of multiphase nonlinear mixed models to define and quantify long-term changes in serum prostate-specific antigen: data from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial.

ABSTRACT

PURPOSE: To test the hypothesis that the pattern of prostate-specific antigen (PSA) change in men diagnosed with high-risk prostate cancer (PrCA) differs from the pattern evident in men diagnosed with low-risk PrCA or those with no evidence of PrCA. METHODS: A retrospective cohort study from which PSA measures were taken before PrCA diagnosis from the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial. Data were fitted using a nonlinear regression model to estimate the adjusted absolute and relative (%) change of PSA. RESULTS: Data on 20,888 men with an average age of 61.61 years were included in the analysis. Of these, the 324 (1.55%) diagnosed with high-risk PrCA had a steeper and earlier transition into an exponential pattern of PSA change than the 1368 men diagnosed with low-risk cancer. At 1 year before diagnosis and/or exit, the average absolute PSA rates were 0.05 ng/mL/year (0.05-0.05), 0.59 (0.52-0.66), and 2.60 (2.11-3.09) for men with no evidence of PrCA, men with low-risk PrCA and those with high-risk PrCA, respectively. CONCLUSIONS: The pattern of PSA change with time was significantly different for men who develop high-risk PrCA from those diagnosed with low-risk PrCA. Further research is required to validate this method and its utilization in PrCA screening.