Background:
The objective of this study was to correlate the failure pattern of localized prostate carcinoma after radiotherapy (rt) with pretreatment (pretx) psa and post-rt nadir psa, using systematic biopsies and serum psa in the assessment of outcome.
Methods:
From january 1990 to february 1994, 207 patients treated with external beam rt were followed prospectively with systematic transrectal ultrasound-guided biopsies and measurements of serum psa levels. three hundred forty-three biopsies were performed, with 4-7 samples taken per session. the distribution of t classification was as follows: 19 patients had t1b, 15 had t1c, 34 had t2a, 79 had t2b/c, 53 had t3, and 7 had t4. median follow-up was 36 months (range, 12-70 months). failures were categorized as biochemical (chemf) (psa > 2.0 ng/ml and > 1 ng/ ml over nadir), local (lf) (positive biopsy and psa > 2), and distant (df). the cox proportional hazards model was used for multivariate analysis (mva).
Results:
Overall, failures were seen in 68 of 207 patients: 20 lf, 24 df, 7 lf + df, and 17 chemf. in univariate analysis, failures correlated significantly with pretx psa, post-rt nadir psa, t classification, and gleason's score (gs). the total failure rate was 12% for t1b, t1c, and t2a; 39% for t2b and t2c; and 60% for t3 and t4 (p < 0.0001). by evaluation with pretx psa, at 36 months the total failure rate was 3% for pretx psa < or = 5 ng/ml 16% for 5.1-10 ng/ml, 32% for 10.1-15 ng/ml, 42% for 15.1-20 ng/ml, 63% for 20.1-50 ng/ml, and 88% for > 50 ng/ml (p < 0.0001). by evaluation with post-rt nadir psa, at 36 months the total failure rate was 4% for nadir psa < or = 0.5 ng/ ml, 26% for 0.6-1 ng/ml, 33% for 1.1-2 ng/ml, and 92% for > 2 ng/ml (p < 0.0001). in mva, nadir psa (p < 0.0001) and t classification (p < 0.0005) were independent predictors for any failure. lf occurred in 13% of patients (27 of 207). for these 27 patients, the categorization of t classification was: t1b/t1c/t2a, 7%; t2b/t2c, 16%; and t3/t4, 15% (p = not significant). in mva, only nadir psa (p = 0.0004) predicted for lf. df occurred in 15% of patients (31 of 207). in mva, nadir psa (p < 0.0001) and t classification (p < 0.0001) predicted for df, with pretreatment psa of borderline significance (p < 0.05). to assess pretx predictors of outcome, post-rt nadir psa was removed from the model. pretx psa then became the dominant variable to predict any failure (p < 0.0001), lf (p = 0.05), chemf (p = 0.0001), and df (p < 0.003), while t classification also predicted for any failure (p = 0.03), chemf (p = 0.05), and df (p < 0.0001).
Conclusions:
Systematic prostate biopsies, performed as part of the rigorous followup of prostate carcinoma after rt, define the patterns of failure and confirm the prognostic value of pretx psa, post-rt nadir psa, and t classification. prior to treatment, pretx psa is the overwhelming independent predictor of failure, but it is surpassed by post-rt nadir psa when this is added to the model.