Below is an abstract from a recent paper by Dr. Klotz, an active
investigator in the area of Watchful Waiting / Active Surveillance
(WW/AS).  By studying a group of men practicing WW/AS over a number of
years, Dr. Klotz was able to define groups at high and low risk for
disease progression.  By looking at serial biopsy results and measuring
PSA doubling times (PSADT) and modeling the PSADT data, he concluded
that if your PSADT was less than about 4.6 years you were more likely
to progress and seek treatment than if your PSADT was greater than
roughly 4.6 years.  Further, he found that good decisions about whether
to seek further treatment could be made after collecting data for a bit
more than 2 years of WW/AS.  This seems like a useful approach to help
reduce overtreatment in low-risk men...Best wishes and good health, ron

J Urol. 2006 Oct;176(4):1392-1398

Modeling Prostate Specific Antigen Kinetics in Patients on Active
Surveillance.

Zhang L, Loblaw A, Klotz L.

Division of Clinical Trials and Epidemiology, and Department of
Radiation Oncology, and Division of Urology, Sunnybrook and Women's
College Health Sciences Centre, University of Toronto, Toronto,
Ontario, Canada.

PURPOSE: Prostate specific antigen doubling time was used to stratify
patients into groups at low and high risk for progression. The prostate
specific antigen kinetics in these 2 groups were modeled.
MATERIALS AND METHODS: In this prospective, single-arm cohort study
patients with favorable clinical parameters (stage T1b-T2b N0M0,
Gleason score 7 or less, prostate specific antigen 15 ng/ml or less)
were conservatively treated with watchful waiting. Evolution of serial
prostate specific antigen measurements over time was estimated from a
general linear mixed model of the natural log of prostate specific
antigen. The corresponding average and individual prostate specific
antigen doubling times were also calculated.
RESULTS: Since November 1995 a total of 231 patients had at least 6
months of followup and at least 3 prostate specific antigen
measurements. Based on prostate specific antigen doubling time and
repeat biopsy, 93 patients fulfilled the criteria for high risk of
disease progression and 138 were defined as low risk. Given the
baseline status of these individuals, 2 reference average lines (high
risk and low risk) were derived to model the evolution of prostate
specific antigen levels and permit more rational decision making
regarding the need for definitive intervention. The average prostate
specific antigen doubling time was 2.97 years (95% CI 2.2-4.4) in
patients allocated to the high risk group and 6.54 years (95% CI
4.8-12.3) in those at low risk.
CONCLUSIONS: By applying the dynamic prognostic rule in combination
with serial biopsy, a rational decision for definitive intervention
based on the risk of disease progression could be optimally recommended
about 2.3 years after initiated surveillance.

PMID: 16952640