title: The serum prostate-specific antigen level three months after radiotherapy for prostate cancer: an early indicator of response to treatment.
abstract: A total of 347 patients with stages A2-C adenocarcinoma of the prostate treated with external beam radiotherapy and with pretreatment and 3-month prostate-specific antigen (PSA) levels were studied to evaluate the potential prognostic significance of the fall in PSA concentration from its baseline (PSAB) to its 3-month (PSA3) level. PSA levels fell in 333 patients (96%). With two exceptions, the patients whose PSA level did not fall had low PSAB and remained without evidence of disease. Since PSA levels fall virtually always, the fact that a fall occurs is of no prognostic value. When the magnitude of the fall relative to baseline was examined, patients with the largest falls had the worst outcomes. This paradoxical result was explained by the relationship between PSAB and PSA3. Regression analysis showed that the fall in PSA level was approximately proportional to the cube root of the baseline value. Thus, patients with high PSAB had high falls, but a high PSAB was an overwhelming predictor for poor outcome. Hence, PSA fall relative to baseline was not a meaningful prognostic factor. The only factor of prognostic value was the absolute PSA3 value. Patients with PSA3 < or = 2 ng/ml fared well at 4 years (freedom from relapse, 91%; incidence of rising PSA profile, 20%); patients with PSA3 > 2, but < or = 10 ng/ml had an intermediate, individually indeterminate outcome (freedom from relapse, 51%; incidence of rising PSA profile, 58%); patients with PSA3 > 10 ng/ml can be said to have failed treatment (freedom from relapse, 50%; incidence of rising PSA profile, 90%).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Radiotherapy, University of Texas M. D. Anderson Cancer Center, Houston 77030.
authors.forename: G K
authors.initials: GK
authors.lastname: Zagars
authors.forename: A
authors.initials: A
authors.lastname: Pollack
mesh_terms: D000230:Adenocarcinoma / Q000097:blood* / Q000175:diagnosis / Q000532:radiotherapy*; D000368:Aged; D000369:Aged, 80 and over; D006801:Humans; D008297:Male; D008875:Middle Aged; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood* / Q000175:diagnosis / Q000532:radiotherapy*; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D017430:Prostate-Specific Antigen