Radical Radiation Therapy in the Management of Prostatic Adenocarcinoma: The Initial Prostate Specific Antigen Value as a Predictor of Treatment Outcome

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Abstract
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)

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