RADICAL RADIATION-THERAPY IN THE MANAGEMENT OF PROSTATIC ADENOCARCINOMA - THE INITIAL PROSTATE-SPECIFIC ANTIGEN VALUE AS A PREDICTOR OF TREATMENT OUTCOME

We studied 161 prostate cancer patients treated by radical irradiation alone without endocrine therapy in whom pretreatment and posttreatmen t prostate specific antigen (PSA) values were measured, and who had a minimum followup of 2 years. Outcome was analyzed in an actuarial fash ion using clinical disease-free survival and biochemical disease-free survival (freedom from an increasing PSA level or a PSA level of great er than 1.0 ng./ml. 2 years following irradiation) as end points. Of t he patients 54% achieved a post-irradiation nadir value in the range 0 to 1.0 ng./ml. and 29% had a nadir value that was undetectably low (l ess than 0.5 ng./ml.). The likelihood of achieving these values was gr eater among patients with early stage than locally advanced tumors. Fo r all T stages the likelihood of being disease-free at 4 years was sub stantially and significantly lower when PSA was used as an end point t han when clinical evaluation alone was used: stages T1 and T2 (85 pati ents) 41% versus 71%, and stages T3 and T4 (76 patients) 15% versus 61 %. For the whole group at 4 years clinical control was 67% but biochem ical control was only 26% (p < 0.05). The likelihood of being free of biochemical evidence of persistent disease at 4 years was a function o f the initial PSA value (PSA less than 4.0 in 81% of the cases, 4.1 to 10.0 in 43%, 10.1 to 20.0 in 31%, 20.1 to 50.0 in 6% and greater than 50.0 in 0%). For stages T1 and T2 cancer patients with an initial PSA level of less than 15 ng./ml. (67% of all early stage cases) this val ue was 65% and it was even higher (73%) when poorly differentiated tum ors were excluded. When the initial PSA level for stages T1 and T2 tum ors was greater than 15 ng./ml. the projected 4-year rate of freedom f rom biochemical failure was only 7%. For stages T3 and T4 cancer patie nts the corresponding figures were 39% for those with an initial PSA l evel of less than 15 ng./ml. and 0% for those with an initial PSA leve l of greater than 15 ng./ml. The prognostic power of the initial PSA l evel was independent of stage, grade, patient age and prior transureth ral resection of the prostate in a multivariate analysis. An initial s erum PSA level of more than 15 ng./ml. is, therefore, a powerful predi ctor of probable failure with conventional radiation therapy. Serum PS A monitoring is a sensitive detector of early relapse. Knowledge of bo th will, in the future, allow the selection of patients for more inten sive initial therapy or for early salvage.