THE EFFICACY OF POSTPROSTATECTOMY RADIOTHERAPY IN PATIENTS WITH AN ISOLATED ELEVATION OF SERUM PROSTATE-SPECIFIC ANTIGEN

Purpose: To determine the efficacy of radiotherapy (RT) in patients wi th an isolated elevation of prostate specific antigen (PSA) after radi cal prostatectomy (RP), Methods and Materials: Between November 1987 a nd May 1993, 53 patients with adenocarcinoma of the prostate were refe rred for pelvic RT for an elevated PSA after RP, No patient had clinic ally or radiographically apparent local or distant disease, nor had an y undergone prior androgen ablation, Patients received a median dose o f 61.2 Gy to the prostatic bed. An undetectable PSA was required to be considered disease free (NED), Univariate and multivariate analyses w ere performed to identify factors predictive of becoming disease free after RT, Results: The median follow-up was 15 months, Of the 53 patie nts, 16 (30%) became NED after RT and 15 (28%) had a declining (n = 11 ) or stable (n = 4) PSA at last evaluation, The median time after RT t o achieve an undetectable PSA was 9.3 months, At 12 and 24 months, the actuarial disease-free survival was 30 and 23%, respectively; actuari al progression-free survival was 71 and 26%, respectively. By univaria te analysis, the last PSA level before RT (i.e., the pre-RT PSA) and a n undetectable PSA after RP were significant predictors of becoming NE D (p = 0.00001 and 0.04, respectively), However, on multivariate analy sis, only the pre-RT PSA remained significant (p = 0.01). The mean pre -RT PSA differed significantly between patients who became NED after R T and those who did not (1.5 +/- 0.2 ng/ml vs, 7.6 +/- 1.6 ng/ml, resp ectively; p = 0.018), Fourteen of 27 (52%) patients with pre-RT PSA le vels less than or equal to 2.5 ng/ml became NED, vs, only 2 of 26 (8%) patients with higher levels, There were no severe acute or late seque lae of RT, Conclusion: Prostatic-bed RT for an elevated serum PSA afte r RP is most effective in patients with a pre-RT PSA less than or equa l to 2.5 ng/ml, Patients with significantly higher PSA values are unli kely to benefit from RT, possibly due to the presence of occult distan t metastases, The optimal therapy for this latter group remains to be determined.