RECURRENCE PATTERNS AFTER RADICAL RETROPUBIC PROSTATECTOMY: CLINICAL USEFULNESS OF PROSTATE SPECIFIC ANTIGEN DOUBLING TIMES AND LOG SLOPE PROSTATE SPECIFIC ANTIGEN

Abstract

We studied the correlation between prostate specific antigen (PSA) doubling time or, equivalently, log slope PSA and clinical recurrence in patients with detectable PSA after radical retropubic prostatectomy who were followed expectantly. In patients with PSA recurrence after radical retropubic prostatectomy log slope PSA was determined from the difference in the 2 log PSA values divided by the time between readings in months. For a given slope the corresponding PSA doubling time was calculated as log x 2 divided by the slope of the log PSA line. When the initial PSA value was considerably greater than 0.4 ng./ml., the log slope PSA plot was extrapolated to determine the time point at which PSA would have become detectable (0.4 ng./ml.). The relationship between these values, and the time and pattern of clinical recurrence were studied. In this series of 77 patients 80% with PSA doubling time of 6 months or greater remained clinically disease-free compared to 64% with PSA doubling time less than 6 months. PSA doubling time had better correlation with time to clinical recurrence after PSA became detectable (p <0.001 Cox proportional hazards model) than Gleason sum, pathological stage or margin status. Biochemical recurrence within 3 months was associated with early clinical recurrence (p <0.002). In addition, short PSA doubling time, that is a high log slope, regardless of the time at which PSA became positive was strongly associated with clinical recurrence (p <0.001). Distant recurrence was invariably associated with short PSA doubling time. Conversely, local recurrence reliably correlated with long PSA doubling time, that is a low log slope. After PSA became detectable PSA doubling time or, equivalently, log slope PSA, was a better indicator of the risk and time to clinical recurrence after radical retropubic prostatectomy than preoperative PSA, specimen Gleason sum or pathological stage. Hormone treatment may be targeted to patients at high risk for early metastatic clinical recurrence, appropriately timed radiation can be offered for proved local recurrence in those with long PSA doubling time and expectant treatment may be proposed for those with long PSA doubling time who remain clinically disease-free. Frequent and expensive imaging does not appear to be cost-effective in this latter group.