Prostate Specific Antigen: A Critical Assessment of the Most Useful Tumor Marker for Adenocarcinoma of the Prostate

Abstract

PSA is a kallikrein-like, serine protease that is produced exclusively by the epithelial cells of all types of prostatic tissue, benign and malignant. Physiologically, it is present in the seminal fluid at high concentration and functions to cleave the high molecular weight protein responsible for the seminal coagulum into smaller polypeptides. This action results in liquefaction of the coagulum. PSA is also present in the serum and can be measured reliably by either a monoclonal immunoradiometric assay or a polyclonal radioimmunoassay. The calculated half-life of serum PSA ranges from 2.2 to 3.2 days and the metabolic clearance rate of this tumor marker follows first-order kinetics. Digital rectal examination, cystoscopic examination and prostate biopsy all can cause spurious elevations of the serum PSA concentration. Conditions such as bacterial prostatitis and acute urinary retention also can falsely elevate the serum PSA level. Because approximately 25% of the patients with BPH only will have an elevated serum PSA concentration and BPH tissue contributes to this PSA value in a variable manner from patient to patient, it is unlikely that PSA by itself will become an effective screening tool for the early diagnosis of prostate cancer. However, if combined with digital rectal examination and/or transrectal ultrasound it may become a vital part of any early detection program. Prostatic intraepithelial neoplasia also may be associated with moderately elevated serum PSA levels. Although there is a direct correlation between the serum PSA concentration and clinical stage, PSA is not sufficiently reliable to determine the clinical stage on an individual basis. This finding also applies to pathological stage. As a result, the preoperative serum PSA concentration cannot be used to decide whether to recommend radical prostatectomy for potential cure. Low preoperative serum PSA concentrations in patients with previously untreated prostate cancers are predictive of a negative bone scan. Thus, in these select patients a staging bone scintigram may not be necessary. With respect to monitoring patients after definitive therapy, PSA is an exquisitely sensitive tumor marker. Irrespective of the treatment modality (radical prostatectomy, radiation therapy or antiandrogen treatment), PSA reflects accurately the tumor status of the patient and is prognostic of eventual outcome; this tumor marker is capable of predicting tumor recurrence months before its detection by any other method. PSA is also a most useful immunocytochemical marker. Its sensitivity and specificity to identify tissue of prostatic origin approach 100%. When compared to PAP, PSA is a more precise and meaningful marker in all clinical situations.(ABSTRACT TRUNCATED AT 400 WORDS)

Serum total PSA and free PSA in breast tumors

“…Routine use of PSA immunoassays has proven the improved rate of detection of prostate cancers. Measurement of various molecular forms of PSA has now been introduced into clinical practice by various researchers [16,17].…”

Patterns of care for metastatic carcinoma of the prostate gland: results of the American College of Surgeons’ patient care evaluation study

“…Screening programs utilizing PSA and TRUS have replaced the traditional digital rectal examination and subsequent perineal and TRUS biopsies. 16 Trends in the treatment of metastatic prostate cancer are somewhat more dif®cult to interpret because of the acknowledged therapeutic value of hormone therapy and the practice of combining forms of hormonal therapy (orchiectomy and exogenous hormonal agents) as well as palliative surgery (TURP) and radiotherapy (for example to metastatic bone sites). Approximately 86% of patients in both 1984 and 1990 were treated with hormone therapy (with or without radiotherapy).…”

Clinical utility of indium 111‐capromab pendetide immunoscintigraphy in the detection of early, recurrent prostate carcinoma after radical prostatectomy

“…[1][2][3][4] Disease may recur locally in the prostatic fossa or regional lymph nodes or at distant sites. The site of disease cancer recurrence may greatly influence the choice between local salvage treatments or systemic therapy.…”

“…15 Generally, distant capromab pendetide scan activity has been reported at higher serum PSA levels. 10,12,13,16 Although anecdotal evidence of uptake of capromab pendetide at serum PSA levels as low as 0.13 ng/mL has been reported, 12,3,16 the utility of the capromab pendetide scan in patients with early biochemical evidence (PSA Ն 4.0 ng/mL) of recurrent prostate carcinoma is not known. In the current study of 255 patients with early evidence of biochemical failure (serum PSA Ն 4.0 ng/mL) after radical prostatectomy, we demonstrate that the capromab pendetide scan may detect recurrent disease irrespective of serum PSA level.…”