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 posttreatment prostate specific antigen (PSA) values were measured, and who had a minimum followup of 2 years. Outcome was analyzed in an actuarial fashion using clinical disease-free survival and biochemical disease-free survival (freedom from an increasing PSA level or a PSA level of greater than 1.0 ng./ml. 2 years following irradiation) as end points. Of the 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 (less than 0.5 ng./ml.). The likelihood of achieving these values was greater among patients with early stage than locally advanced tumors. For all T stages the likelihood of being disease-free at 4 years was substantially and significantly lower when PSA was used as an end point than when clinical evaluation alone was used: stages T1 and T2 (85 patients) 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 biochemical control was only 26% (p < 0.05). The likelihood of being free of biochemical evidence of persistent disease at 4 years was a function of 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 value was 65% and it was even higher (73%) when poorly differentiated tumors were excluded. When the initial PSA level for stages T1 and T2 tumors was greater than 15 ng./ml. the projected 4-year rate of freedom from biochemical failure was only 7%. For stages T3 and T4 cancer patients the corresponding figures were 39% for those with an initial PSA level of less than 15 ng./ml. and 0% for those with an initial PSA level of greater than 15 ng./ml. The prognostic power of the initial PSA level was independent of stage, grade, patient age and prior transurethral resection of the prostate in a multivariate analysis. An initial serum PSA level of more than 15 ng./ml. is, therefore, a powerful predictor of probable failure with conventional radiation therapy. Serum PSA monitoring is a sensitive detector of early relapse.(ABSTRACT TRUNCATED AT 400 WORDS)

Duke Scholars

Author Christopher G. Willett Radiation Oncology