Longitudinal Evaluation of Prostate-Specific Antigen Levels in Men With and Without Prostate Disease

Characteristics of prostate cancers detected in a multimodality early detection program. The Investigators of the American Cancer Society-National Prostate Cancer Detection Project

BACKGROUND

Few data are available to describe the clinical and pathologic characteristics of prostate cancers detected through early detection programs. The American Cancer Society National Prostate Cancer Detection Project (ACS-NPCDP) is a multimodality, multicenter study of the feasibility of early prostate cancer detection using digital rectal examination (DRE), transrectal ultrasound (TRUS), and prostate specific antigen (PSA). One hundred fifty-six prostate cancers are available from this project for analysis.

METHODS

The ACS-NPCDP is a prospective, comparative study of a cohort of 2,999 men between 55 and 70 years of age not suspected of having prostate cancer. DRE, TRUS, and PSA are performed for each subject on an annual basis for as long as 5 years. Biopsies are performed on the basis of recommendations from DRE or TRUS results. Although elevated PSA alone was not typically a basis for biopsy, in some instances biopsies were recommended because of the degree of elevation in PSA. Diagnoses are confirmed by participating pathologists and by pathologic analysis.

RESULTS

A small proportion of cancers detected were advanced in terms of the clinical stage at time of diagnosis. A total of only six cancers were stage C1 to D1, and five of these were preexisting cancers detected at the first examination. Cancers detected by DRE tended to be more advanced than those found on the basis of only TRUS or PSA. A large proportion of patients received curative therapy, involving radical prostatectomy for 67.9% and radiation therapy for 17.9%. Of 100 men presumed to have organ confined disease and treated by prostatectomy, 64 actually proved to have localized cancer, a rate of upstaging of 36.0%. PSA level and PSA density were associated with the detection of organ confined cancer, but several advanced cancers had PSA levels in the normal range, limiting the usefulness of these measures for staging.

CONCLUSIONS

The cancers resulting from this multimodality detection effort represented a spectrum of pathologic findings. These data, however, suggest that early detection interventions in men not suspected to have prostate cancer will yield tumors with a favorable stage distribution that are likely to benefit from treatment. Further follow-up evaluation is needed to determine whether these benefits are reflected in long-term mortality and survival experience.

The status of prostate cancer early detection

Prostate cancer represents an increasing public health burden that may be controlled by early detection interventions. Several studies using transrectal ultrasound (TRUS), prostate-specific antigen (PSA), and digital rectal examination (DRE) in men without known prostate disease have been reported. Recent studies are reviewed, and recent preliminary results of the American Cancer Society-National Prostate Cancer Detection Project (ACS-NPCDP) are presented. Results show that the rate of early prostate cancer detection can be increased by coordinated use of TRUS, PSA, and DRE. The ACS-NPCDP data indicate that the positive predictive value of recommendations to biopsy is improved when based on a combination of studies. Examination by TRUS alone is least specific and least cost-effective, whereas the combination of PSA and DRE is less costly and more specific with equal sensitivity to cancer. Additional data are needed to determine if prostate cancer death rates will be altered by early detection interventions. Physicians and patients need to be informed of the possible risks and benefits of early detection interventions.

Screening for prostatic carcinoma with prostate specific antigen: results of the second year

Prostate specific antigen (PSA) has been shown to be useful alone and in conjunction with other tests in the diagnosis of prostatic carcinoma. Previously, we demonstrated that a PSA level of greater than 4.0 ng./ml. as the initial diagnostic test in a screening population results in a detection rate of 2.6 and positive predictive value of 30.5. In the present investigation we performed digital rectal examination and transrectal ultrasound as well as ultrasound guided biopsy in men who in the initial year of the screening study had a PSA level of less than 4.0 ng./ml. but on evaluation 1 year later they had a 20% increase in the PSA level. A total of 701 subjects returned for year 2 of the protocol and 260 (37.1%) demonstrated more than a 20% increase in PSA value. Biopsy was performed in 82 men and carcinoma was detected in 14 (17.1%). Of the men with carcinoma 12 had a second year PSA level of less than 4.0 ng./ml. Radical prostatectomy was performed in 8 patients, 7 of whom had organ confined disease or tumor penetrating the capsule with negative margins. We conclude that a 20% annual change in PSA level may identify men at significant risk for prostatic carcinoma and that patients so identified have favorable pathological stage.

Observations on the doubling time of prostate cancer. The use of serial prostate-specific antigen in patients with untreated disease as a measure of increasing cancer volume

BACKGROUND

The serum marker prostate-specific antigen (PSA) has been shown to be proportional to the volume of prostate cancer (Yang polyclonal assay). One gram of cancer on average produces 3.5 ng/ml of PSA elevation. Thus, changes in PSA in untreated patients should reflect tumor growth rate and the shape of the growth curve.

METHODS

Forty-three patients with previously untreated prostate cancer had serial PSA determinations during a period of at least 12 months (mean, 30 months; range, 12-63 months). There was no treatment between the initial and final PSA. PSA was measured five or more times in half of these patients. Log-PSA values were plotted versus time, tested for linearity, and compared between different clinical stages and histologic grades.

RESULTS

PSA values increased with time in 86% of patients but remained stable in 14%. The increase of PSA was exponential (log-linear) throughout the measured interval. Doubling times were faster in patients with higher disease stages and grades. Seventy-nine percent of all patients had a doubling time of more than 24 months. Twenty of 28 cancers thought to be clinically organ confined doubled at rates exceeding 48 months. Tumor doubling times were overestimated in patients with large-volume benign prostatic hyperplasia because hyperplasia increases serum PSA at an average rate of 0.3 ng/ml.

CONCLUSIONS

The authors conclude that prostate cancer has a constant (log-linear) growth rate that is very slow. This extraordinarily slow doubling time has substantial consequences for therapeutic decisions and for screening programs.

Prostate-specific antigen, digital rectal examination, and transrectal ultrasonography: their roles in diagnosing early prostate cancer

In this article, we review the current status of early detection of prostate cancer. From existing data in the medical and urologic literature, we developed an algorithm that uses the three current methods of detection: digital rectal examination (DRE), determination of the prostate-specific antigen (PSA) value, and transrectal ultrasonography (TRUS). Prostatic malignant disease is an increasing medical problem in the United States. The potential for cure is optimized by early detection and treatment of organ-confined disease. Mass screening for prostate cancer in asymptomatic men cannot be advocated until a decrease in the mortality rate is established by randomized, controlled studies; however, these data will be unavailable for at least 15 years. In the meantime, clinicians must prudently use DRE, PSA, and TRUS for early detection. Current data indicate that the PSA level is as effective as or more effective than DRE for the detection of prostate cancer. These two methods do not always detect the same malignant tumor; therefore, the combined use of DRE and PSA testing provides a more complete evaluation of the prostate gland for malignant involvement. TRUS is more costly and does not add appreciable detectability when results of both the DRE and the PSA determination are normal. Thus, TRUS is best reserved for patients who have abnormal results of DRE or increased PSA values.

Prostate-specific antigen and prostate volume: a meta-analysis of prostate cancer screening criteria

OBJECTIVE

To establish the value of serum prostate-specific antigen (PSA) and prostate-specific antigen per unit volume of prostate gland (PSAD) in detecting prostate carcinoma (CaP) in a hypothetical screening algorithm, a meta-analysis of the sensitivities, specificities, predictive values and likelihood ratios were combined from the published data.

DATA SOURCES

Journal articles identified by a MEDLINE database search from 1988 to October 1992, using prostate-specific antigen as a key word were used to calculate the distribution of PSA in healthy men, men with benign prostatic hyperplasia (BPH) and men with prostate carcinoma (CaP).

STUDY SELECTION

Only studies that contained the specified serum PSA values and patient outcomes were included.

DATA EXTRACTION

The distributions of the serum PSA were plotted versus serum PSA for healthy men (2567), men with BPH (798) and men with CaP (835) from the abstracted data. Prostate volume distributions were estimated from the published transrectal ultrasound (TRUS) calculations.

DATA SYNTHESIS

Hypothetical cohorts of 1,000 men between the ages of 60 and 70 years were screened using three different screening decision algorithms. Using a serum PSA cutoff of 3.0 ng/ml for referral for transrectal biopsy, 59 of 80 (74%) CaP would be detected and 21 (26%) would be missed. 209 transrectal biopsies would be performed, and 150 (72%) of them would be negative for CaP. Using a serum PSA cutoff of 4.0 ng/ml, 52 of 80 (65%) CaP would be detected and 28 (35%) would be missed. 146 transrectal biopsies would be performed, and 94 (64%) of them would be unnecessary. Using a cutoff of 2.0 ng/ml for serum PSA and 0.1 ng/ml/cc for PSAD, 55 of 80 (69%) of the cancers would be detected and 25 (31%) would be missed. Only 84 transrectal biopsies would be performed, and 29 (35%) of them would be negative for cancer.

CONCLUSION

This algorithm maximizes the number of cancers detected (true-positive cases) and at the same time reduces the number of false-positive cases, minimizing the number of patients who would have to receive an unnecessary transrectal biopsy, compared to using a serum PSA cutoff of 3.0 or 4.0 ng/ml.

The effect of finasteride on prostate-specific antigen in men with benign prostatic hyperplasia

Finasteride is a specific 5-alpha-reductase inhibitor that has been shown to reduce prostate size and decrease serum levels of prostate specific antigen (PSA). Among men who received finasteride (5 mg/day) for 12 months in North American clinical trials and in whom prostate cancer was not diagnosed the median percentage change in PSA was -50% (5-95% range: -81% to +20%). At baseline 72% had PSA < or = 4.0 ng/ml and 93% had PSA < or = 10.0 ng/ml. After 12 months on finasteride, 75% had PSA < or = 2.0 ng/ml and 95% had PSA < or = 5.0 ng/ml. Thus, the proportion of BPH patients with PSA levels of 2.0 ng/ml and 5.0 ng/ml after 12 months of treatment was comparable to the proportion with pretreatment PSA levels of 4.0 ng/ml and 10.0 ng/ml. Among the 10 men in these trials subsequently diagnosed with prostate cancer while on long-term finasteride therapy (5 mg/day), the median percentage change in PSA was -26% (range: -48% to +12%). Limited experience with finasteride in men with prostate cancer suggests that the reduction in PSA of malignant origin appears to be no greater than the percentage reduction in PSA of benign origin. These effects on PSA have not been shown to confer any therapeutic benefit. Physicians using finasteride should be aware of its effect on PSA levels.

Prostate-specific antigen and diagnosing early malignancies of the prostate

Prostate-specific antigen 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. Prostate-specific antigen is also present in the serum and can be measured reliably by several different assays. Although the protein is prostate-specific, it is not prostate-cancer-specific. As a result, benign conditions such as benign prostatic hyperplasia, prostatitis and infarction, as well as prostatic intraepithelial neoplasia, can be associated with elevated serum levels of prostate-specific antigen. Approximately 25% of men with benign prostatic hyperplasia have an elevated serum value of prostate-specific antigen, whereas 35% to 40% of patients with organ-confined prostate cancer have a level within the reference range. Prostate-specific antigen can identify some cancers not detectable by digital rectal examination; alternatively, this examination can identify cancers not detectable from the serum prostate-specific antigen concentration. Thus, the most complete evaluation of the prostate gland is achieved when both the prostate-specific antigen value and the digital rectal examination are used. The density and the rate of change of serum prostate-specific antigen are new concepts to improve the ability of prostate-specific antigen to detect early prostate cancer. Preliminary results are encouraging, but additional studies are required to determine the true usefulness of these new variables. Thus, in 1992, determination of the prostate-specific antigen value is a valuable new tool for the practicing physician and will be instrumental in our campaign to diagnose clinically significant prostate cancer at an early, curable stage.

Cancer detected incidental to simple prostatectomy (stage A1)

The incidence of stage A (incidental) adenocarcinoma of the prostate in transurethral resection (TUR) specimens is approximately 16%. This paper discusses the criteria for differentiating stage A1 versus stage A2 tumor, based on tumor volume and grade. Both the short-term (4 year) and long-term (8-10 year) natural history of untreated stage A1 prostate cancer are examined. Options to follow patients expectantly are presented. These include digital rectal examination and transrectal ultrasound. Specific problems relating to analyzing transrectal ultrasounds in patients who have had a prior TUR are addressed. Also, the unique aspects of transrectal ultrasound for stage A1 disease as it relates to the location of the lesion are expanded upon. The third option in the management of stage A1 disease is to monitor serum prostate specific antigen (PSA) levels. Areas covered include the sensitivity and specificity of PSA in general, and, in specific, serum PSA levels following TUR for stage A1 disease as a predictor of residual tumor. New data on a small group of patients who underwent delayed radical prostatectomy following diagnosis of stage A1 disease, where PSA data was available, are presented. The rationale for following patients with stage A1 disease by monitoring their serum PSA levels is supported by data from a group of men with normally sized prostates, benign prostatic hyperplasia, or cancer where longitudinal serum PSA levels were available. Finally, the option of radical prostatectomy for stage A1 disease is put forth. Data include a study of a large group of radical prostatectomy specimens performed for stage A1 disease.(ABSTRACT TRUNCATED AT 250 WORDS)