Background: For the moment, there is uncertainty about the usefulness of early treatment of localized prostate carcinoma, uncertainty about whether some patients with early cancer can be managed expectantly, and uncertainty about how such patients might be recognized.
Methods: The authors studied serial values of prostate specific antigen (PSA) in 94 Japanese men with diagnosed prostate carcinoma and who were managed by watchful waiting. Their median follow-up duration was 32 months (range, 1.6-118). The authors used a log-linear model to fit the values of PSA over time, and then they used the Cox survival model to relate the intercept (PSA amplitude) and slope (relative velocity) to observed local or systemic outcomes that were independent of PSA.
Results: The authors found that the log-linear model fit the serial values of PSA during watchful waiting very well. Prostate specific antigen amplitude related significantly to T classification (P = 0.0006), but not to grade (P > 0.2), and the relative velocity related significantly to both T classification (P = 0.009) and to grade (P = 0.02). Although the T classification, histologic grade, and log(PSA) at diagnosis were associated significantly with time to outcome, the combination of amplitude and relative velocity provided more information. These 2 PSA parameters resulted in a higher model likelihood ratio, and their individual P values in the Cox model were 0.0005 and 0.005, respectively. With these two in the Cox model, T classification, grade, log(PSA), and PSA doubling time provided no further significant information.
Conclusions: A log-linear model seems to fit serial measurements of PSA during watchful waiting, and preliminary results suggest that both the amplitude and the relative velocity relate closely to clinical outcomes.
Copyright 2002 American Cancer Society.