PROSTATE-SPECIFIC ANTIGEN DOUBLING TIMES ARE SIMILAR IN PATIENTS WITHRECURRENCE AFTER RADICAL PROSTATECTOMY OR RADIOTHERAPY - A NOVEL ANALYSIS

Purpose: Same investigators have analyzed the rate of growth of prosta te cancer that has recurred after definitive radiotherapy or radical p rostatectomy using serum prostate-specific antigen (PSA) doubling time s (DT). We examined all PSA values in recurrent patients to determine the pattern and rate of increase in PSA after radiation therapy and ra dical prostatectomy. patients and Methods: Charts of 96 recurrent radi cal prostatectomy patients (mean age, 62.8 years; range, 47 to 76) and 42 recurrent radiation therapy patients (mean age, 67.2 years; range, 52 to 83) were reviewed. All available PSA values between the date of operation/radiation treatment and last follow-up evaluation or the in itiation of second-line therapy are included. Rate of PSA DT was not a ssumed to be constant over time; it was instead allowed to vary. We us e a piecewise linear random-coefficients model in time for log(PSA), w hich allowed different mean models for both treatments. Results: The P SA DT in the first year after radiation therapy was -1.17 years, which reflects the continuous decline in PSA in the average patient during the first year after radiotherapy despite eventual biochemical progres sion. In contrast, the PSA DT in the radical prostatectomy group was 0 .66 in the first year. In year 2, after radiation therapy the PSA DT w as lengthy at 1.82 years, significantly longer (P=.0025) than in the r adical prostatectomy group (0.76 years). After year 2, there were no s ignificant differences between the two groups (P>.05). Conclusion: A p iecewise linear random-coefficients model enables interval analysis of PSA DT. While the PSA DT after radiation therapy and radical prostate ctomy are different in the first 2 years, the rate of increase in PSA appears to be similar in the two groups after year 2, which suggests t he rate of growth of cancers that recur after radiation therapy and ra dical prostatectomy is similar. (C) 1998 by American Society of Clinic al Oncology.