WO1997039351A1

WO1997039351A1 - Novel methods for the prediction and early detection of prostatic adenocarcinoma

Info

Publication number: WO1997039351A1
Application number: PCT/US1997/006787
Authority: WO
Inventors: Herbert B. Carter; Daniel W. Chan; Alan W. Partin; Albert A. Luderer; Grant D. Carlson; Robert P. Thiel; Jay D. Pearson
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-04-12
Filing date: 1997-04-11
Publication date: 1997-10-23
Anticipated expiration: 1998-10-12

Abstract

The present invention relates to novel methods for the prediction and early detection of prostatic adenocarcinoma (CAP) by differentiating a benign prostatic conditions (BPD), such as benign prostatic hyperplasia, prostatitis, or glandular atrophy. In particular, the present invention can be used as a longitudinal screening test for male patients who are younger than patients typically receiving serum or blood testing today. The total prostate specific antigen (PSA) level and the free PSA levels in the blood or serum of the patient are measured. The proportion of free PSA to total PSA is calculated. If this proportion is equal to or less than about from 8 % to 12 %, preferably 10 %, then the patient is considered to be a high risk candidate for CAP, and thus, should receive at least an annual detailed evaluation of the status of his prostate. For patients having this proportion greater than from about 8 % to 12 %, preferably 10 %, the risk of CAP is reduced sufficiently so that the time between such examinations can be extended beyond current practice.

Description

NOVEL METHODS FOR THE PREDICTION AND EARLY DETECTION OF PROSTATIC ADENOCARCINOMA

TECHNICAL FIELD

The present invention relates to novel methods for the prediction and early detection of prostatic adenocarcinoma (CAP) by differentiating a benign prostatic condition, (BPD), such as benign prostatic hypeφlasia, prostatitis, or glandular atrophy. In particular, the present invention can be used as a longitudinal screening test for male patients who are younger than patients typically receiving serum or blood testing today. The total prostate specific antigen (PSA) level and the free PSA levels in the blood or serum ofthe patient are measured. The proportion of free PSA to total PSA is calculated. If this proportion is equal to or less than about 10%, then the patient is considered to be a high risk candidate for CAP, and thus, should receive at least an annual detailed evaluation ofthe status of his prostate. For patients having this proportion greater than 10%, the risk of CAP is reduced sufficiently so that the time between examinations can be extended beyond current practice.

BACKGROUND ART

PSA is recognized as a molecular marker for CAP. Blood or serum based immunoassays measuring the total PSA level have been commercially available for a number of years. From clinical experience, total PSA tests have become generally accepted as being predictive of CAP if the total PSA level is greater than 10.0 ng/ml. Total PSA values between 0.0 ng/ml and about 3.9 ng/ml have been considered generally predictive of no disease being present, with a value of about 3.5 ng/ml being used for men under 60 years old and about 2.5 ng/ml being used for men under 50 years old. (See Oesterling, J. E., Cooner, W. H., Jacobsen, S. J., Guess H. A., and Lieber, M.M.: ''Influence of Patient Age on the Serum PSA Concentration and Important Climcal Observations ^■": Urol. Clin. North Am.; Vol. 20: 671-680, 1993.) However, the detection of a high amount of total PSA does not necessarily mean that a patient has CAP. In order to distinguish CAP from BPD, a total PSA test has to satisfy two elements: a high sensitivity — the ability to detect disease when present, and a high specificity ~ the ability to detect true negatives and avoid false positives.

PSA is primarily organ-specific, not cancer specific. Thus, PSA in blood or serum can result not only from CAP, but also from normal or hyperplastic prostate tissues. Historically, a total PSA test cannot reliably distinguish BPD from CAP at less than 10.0 ng/ml. Studies have found that 43% (136/319) of patients with organ-confined CAP have a total PSA value within the normal range of less than 4.0 ng/ml. Moreover, about 25% (148/597) of men with BPD have a total PSA value above 4.0 ng/ml. (See Oesterling, J. E.: "Prostate Specific Antigen: A

Critical Assessment ofthe Most Useful Tumor Marker for Adenocarcinoma ofthe Prostate", J. Urol., Vol:145: 907-923, 1991.) Standard medical practice is to biopsy patients over 60 years old having total PSA levels of between 4.0 ng/ml and 10.0 ng/ml because about 30% of those patients have CAP. Likewise, patients between 50 years and 60 years old whose total PSA falls between 3.5 ng/ml and

10.0 ng/ml and patients under 50 years old whose total PSA falls between 2.5 ng/ml and 10.0 ng/ml are also biopsied under current medical practice.

One proposed method for detecting the presence of CAP is disclosed in U. S. 5,501,983 to Hans Lilja, et alia. In general, the Lilja patent discloses using immunoassays to measure free PSA and a complexed form of PSA. Free PSA is a 33 kDa single chain glycoenzyme that is produced by the epithelial cells lining the acini and prostatic ducts ofthe prostate gland. Complexed PSA refers primarily to a 90kDa complex of PSA bound to alpha 1- antichymotrypsin (ACT) protein. Free PSA and complexed PSA, and their proportions are applied in the diagnosis of patients with CAP. Throughout, the specification discloses using a combination of a free PSA to total PSA (F/T) proportion and a complexed PSA to total PSA (C/T) proportion for use in diagnosing CAP.

More recently, the use of proportions of free PSA to total PSA to determine if a patient currently has CAP or BPD has been disclosed. (See Luderer, A. A., et alia, "Measurement ofthe Proportion of Free to Total Prostate-Specific Antigen Improves Diagnostic Performance of Prostate-Specific Antigen in The Diagnostic Gray Zone of Total Prostate-Specific Antigen", Urol., Vol. 46: 187- 194, 1995.) One measures the total PSA level in the blood or serum ofthe patient as well as the free PSA level in the blood or serum of a patient, but only if he has a total PSA level of between about 2.5 ng/ml and about 10.0 ng/ml. If the patient has a total PSA level below 2.5 ng/ml, then he is presumed not to have a malignant lesion. If the patient has a total PSA level above 10.0 ng/ml, then he is presumed to have CAP and must be biopsied. The patient is presumed to have BPD if the calculated proportion of free PSA to total PSA is equal to or greater than about 25%. Confirmation ofthe significant improvement of diagnostic specificity by this work has been reported. (See Catalona, W. J., et alia, "The Valuation of Percentage of Free Prostate Specific Antigen to Improve Specificity of Prostate Cancer Screening", JAMA 274: 1214-1220, 1995.)

With respect to attempts to push back the discovery of CAP in a patient, researchers have discovered that the rate of change in PSA (PSAV or PSA velocity) is an important early marker for the development of cancer. (See Carter, H. B., et alia, "Longitudinal Evaluation of Prostate-Specific Antigen Levels in Men With and Without Prostate Disease", JAMA 267:2215-2220, 1992.) The optimal time at which PSAV should be evaluated is considered to be between 1.5 and 2.0 years. (See Carter, H. B., et alia, "What Is the Shortest Time Interval Over Which Prostate Specific Antigen Velocity Should Be Measured!", J. Urol 153:136A (764), 1995.) However, PSAV is age dependent, and the use of PSAV alone for cancer detection requires age adjustment manipulations that have not been not resolved. (See Pearson, J. D., et alia, "Sensitivity and Specificity for Age-Specific Reference Ranges for Prostate Specific Antigen Velocity ", J. Urol 153:157A (947), 1995.)

DISCLOSURE OF THE INVENTION

The present invention relates to novel methods for the prediction and early detection of prostatic adenocarcinoma (CAP) by differentiating patients at a higher risk of getting CAP from normal patients and patients having or likely to get a benign prostatic condition, (BPD), such as benign prostatic hyperplasia, prostatitis, or glandular atrophy. In particular, the present invention can be used as a longitudinal screening test for male patients who are younger than patients typically receiving serum or blood testing today. Although one need not be limited to any particular time interval, it is foreseen that the present screening technique would be used on an either an annual or biannual basis for males at least 35 years old.

To perform the longitudinal screen, one must measure the total PSA level and the free PSA level in the blood or serum of a patient. The proportion of free PSA to total PSA is calculated. If this proportion is equal to or less than about from 8% to 12%, preferably 10%, then the patient is considered to be a higher risk candidate for CAP, and thus, should receive at least an annual detailed evaluation of the status of his prostate. For patients having this proportion greater than from about 8% to 12%, preferably 10%, - a lower risk patient, the risk of CAP is reduced sufficiently so that the time between detailed examinations can be extended beyond current practice. (For the purposes ofthe present invention, the term "higher risk" includes a person having a statistically significant likelihood of developing detectable CAP within a range of up to about ten years in the future, while the term "lower risk" includes a person having a less than five percent chance of developing detectable CAP within the same time interval.)

The present invention also includes reports as a result of having a CAP longitudinal screening test according to the present method. A report for a selection for a male human patient as being at a higher risk for CAP comprises a listing of a calculated free PSA to total PSA proportion equal to or lesser than about from 8% to 12%, preferably 10% and an identification ofthe patient. A report for a selection for a male human patient as being at a lower risk for CAP comprises a listing of a calculated free PSA to total PSA proportion greater than about 8% to 12%, preferably 10%, and an identification ofthe patient.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE 1 is a diagrammatic view ofthe total PSA assay used in the present invention.

FIGURE 2 is a diagrammatic view ofthe free PSA assay used in the present invention.

FIGURE 3 is a graph showing a statistical mixed effects analysis of using total PSA tests and years before a diagnosis of CAP.

FIGURE 4 is a graph showing a statistical mixed effects analysis of using free PSA tests and years before a diagnosis of CAP.

FIGURE 5 is a graph showing a statistical mixed effects analysis of using a calculated free PSA to total PSA proportion and years before a diagnosis of CAP.

FIGURE 6 is a graph the performance of a free PSA to total PSA proportion with respect to sensitivity, specificity, and lead time before clinical diagnosis. FIGURE 7 is a graph of a the performance of calculated free PSA to total PSA proportions with respect to lead times.

BEST MODES FOR CARRYING OUT THE INVENTION

Assays In preferred embodiments described below, the present method uses three specific immunoassays, however, any specific binding assay that measures either free PSA or total PSA is suitable for the present methods. The first two assays are total PSA sandwich immunoassays. One is manufactured by Tosoh Medics, Inc. (Tosoh) of Foster City, California, the other by Hybritech, Inc. of San Diego, California. These assays are a type of immunoenzymetric assay using dual murine monoclonal antibodies. FIGURE 1 shows diagrammatically how, in the final sandwich configurations, this first assay captures both free PSA (10) and complexed PSA/ACT (12) using a capture antibody (14) and an enzyme labeled antibody (16).

The third assay is a free PSA immunoassay manufactured developed by Immuno Corp. for Dianon Systems. Inc. (Dianon) of Stratford, Connecticut. This free PSA test is designed to detect free PSA in serum using an IRMA coated tube format. Free PSA binds to a tube coated by a monoclonal antibody which selectively binds free PSA but not complexed PSA. After washing, an I '25 labeled polyclonal antibody against free PSA is reacted with the bound free PSA. The physician is given a result that expresses a proportion of free PSA to total PSA. FIGURE 2 shows diagrammatically how in the final sandwich configuration, this second assay captures free PSA (10), but the capture antibody (14) does not specifically bind to the complex ofthe PS A/ ACT complex (12) and radiolabelled antibody (16).

Example Total PSA and free PSA serum levels were assayed in a longitudinal retrospective case controlled study of 78 patients. Each subject had serum samples taken at two year intervals for twenty years prior to any diagnosis of prostate status. All serums were cryogenically stored at -70°C. Classified as "normal", 26 males were identified as being between 50 years and 81 years old at diagnosis. (The age median at diagnosis was 61.2 years old.) The median number of years of follow-up prior to diagnosis was 15.4. These patients had a normal digital rectal examination (DRE), and had no prior history of CAP. Classified as "BPD", 29 males were identified as being between 55 years old and 89 years old at the time of diagnosis. (The age median at diagnosis was 77.4 years old.) The median number of years of follow-up prior to diagnosis was 9.4 . These patients had BPD histologically confirmed by simple needle prostate biopsy, and no history of cancer. Classified as "CAP", 23 males were identified as being between 54 years old and 85 years old at the time of diagnosis, having primary CAP histologically confirmed by simple needle prostate biopsy. (The age median at diagnosis was 74.6 years.) The median number of years of follow-up prior to diagnosis was 13.2 . None of these patients received any form of prostate-related treatment prior to diagnosis.

Total PSA was measured using either the Hybritech assay or the Tosoh assay described above, in accordance with the manufacturer's instructions. Free

PSA was measured using the Dianon assay described above, in accordance with the manufacturer's instructions. Both total PSA levels and free PSA levels were measured from samples at study entry, midway to diagnosis, and at final diagnosis.

TABLE 1

Normal BPD CAP

Total PSA (ng/ml)

Median 0 0..99 2 2..44 5.0

MMiinniimmuumm 00 0...222 0 0..22 0.9

Maximum 3 3..66 7 7..00 24.9 Free PSA (ng/ml)

Median 0.14 0.48 0.62

Minimum 0.07 0.08 0.15

Maximum 0.64 1.99 2.71

F/T Proportion (%)

Median 19 15 10

Minimum 9 7 4

Maximum 55 40 23

Explanation of FIGURES

The results ofthe total PSA testing and free PSA testing of patient samples over time were analyzed to determine if any relationship could be revealed that was predictive of a patient being at either a higher risk or lower risk of getting CAP. For FIGURES 3 to 7, longitudinal mixed effects analyses were performed. Such an analysis comprises a mixed effects regression model that controls for concomitant variables when assessing the effect of PSA's interest. In these models, the total PSA level, the free PSA level, or the calculated free PSA to total PSA proportion is treated as a random variable to account for the natural heterogeneity of these time dependent values. The regressed PSA value has a confidence interval of 95% which is constructed using the parameters ofthe mixed effect model. The criteria for a patient being positive for purposes of determining lead times from these analyses was that if a calculated free PSA to total PSA proportion was ever less than about 10%, then the patient was considered as positive for CAP.

FIGURE 3 shows the results of a statistical longitudinal mixed effects analysis ofthe total PSA testing. Separation of CAP cases and BPD cases from normal cases does not occur until approximately 2.9 years before diagnosis. Thus, total PSA testing is not an effective early predictive marker for a longitudinal screen that differentiates CAP. FIGURE 4 shows the results of a statistical longitudinal mixed effects analysis ofthe free PSA testing. While separation of CAP cases from normal cases occurs at approximately 8 years before diagnosis, separation of CAP cases from BPD cases does not occur until diagnosis.. Thus, one must conclude reasonably that free PSA testing is not an effective early predictive marker for a longitudinal screen that differentiates CAP.

FIGURE 5 shows the results of a statistical longitudinal mixed effects analysis ofthe calculation of a free PSA to total PSA proportion. Separation of

CAP cases from BPD cases and normal cases occurs at least approximately 10 years before diagnosis. Thus, one must conclude reasonably that calculated free PSA to total PSA proportion is an effective early predictive marker for a longitudinal screen that differentiates CAP.

The performance ofthe use of a free PSA to total PSA proportion with respect to lead times for predicting CAP is disclosed in FIGURE 6. A calculated free PSA to total PSA proportion in the range of from about 8% to 12%, preferably 10%, occurs at a combined maximum of sensitivity and specificity. The lead time within this range is at about at least 10 years before CAP diagnosis. This lead time is particularly important in that identifying a patient before CAP has penetrated the prostatic capsule makes a major difference in the options available to the physician for treatment. Prior to penetration, the physician can select from nerve-sparing prostatectomy, radical prostatectomy, and chemotherapy. After penetration, chemotherapy is the only choice, and a limited one at best, once the cancer has metastasized to varied locations in the patient's bones.

The difference in predictive power is best seen in FIGURE 7, where clearly either free PSA testing or total PSA testing alone cannot support a conclusion that a patient is at a higher risk or a lower risk of getting CAP in the future. In a time of increasing concern about health care costs and unnecessary medical procedures, the present method provides a powerful cost-saving clinical tool to the urologist and can be of great comfort to the patient. Patients can begin to be screened at an early age for CAP, 35 years old, which is about 15 years sooner than currently possible. Using the present method, about 40% of the patients who will get CAP will receive a diagnosis at least 10 years earlier than possible before the present invention, (60% at least 6 years sooner), simply due to their identification as being at a higher risk for CAP as a result of a longitudinal screening according to the present invention. Moreover, the remaining percentage can be put in a lower risk category, requiring a continuation ofthe screening, and a concomitant peace of mind.

All publications or unpublished patent applications mentioned herein are hereby incoφorated by reference thereto.

Other embodiments ofthe present invention are not presented here which are obvious to those of skill in the art, now or during the term of any patent issuing herefrom, and thus, are within the spirit and scope ofthe present invention.

Claims

CLAIMS:

1. A method for longitudinally screening male human patients differentially between being at a higher risk or a lower risk for prostatic adenocarcinoma (CAP) comprising: a) measuring the total prostate specific antigen (PSA) level in the blood or serum ofthe patient; b) measuring the free PSA level in the blood or serum of a patient; c) calculating the proportion of free PSA to total PSA; and d) designating the patient as being at a higher risk if the calculated proportion of free PSA to total PSA is equal to or lesser than about from 8%to 12% or at a lower risk if the calculated proportion of free PSA to total PSA is less than about from 8% to 12%.

2. The method of Claim 1 wherein the calculated proportion of free PSA to total PS A is equal to or lesser than about 10%.

3. The method of Claim 1 wherein the total PSA level is greater than or equal to

2.0 ng/ml.

4. The method of Claim 1 wherein the total PSA level is greater than or equal to 4.0 ng/ml.

5. The method of Claim 2 wherein the total PSA level is greater than or equal to 2.0 ng/ml.

6. The method of Claim 2 wherein the total PSA level is greater than or equal to 4.0 ng/ml.

7. A report for a selection for a male human patient as being at a higher risk for CAP as a result of a longitudinal screening of the free PSA level and the total

PSA level in the patient comprising a listing of a calculated free PSA to total PSA proportion equal to or lesser than about from 8 % to 12% and an identification ofthe patient.

8. The report of Claim 7 wherein the calculated proportion of free PSA to total PSA is equal to or lesser than about 10%.

9. The report of Claim 7 wherein the total PSA level is greater than or equal to 2.0 ng/ml.

10. The report of Claim 7 wherein the total PSA level is greater than or equal to 4.0 ng/ml.

1 1. A report for a selection for a male human patient as being at a lower risk for CAP as a result of a longitudinal screening ofthe free PSA level and the total PSA level in the patient comprising a listing of a calculated free PSA to total

PSA proportion greater than about from 8% to 12% and an identification ofthe patient.

12. The report of Claim 1 1 wherein the calculated proportion of free PSA to total PSA is equal to or lesser than about 10%.

13. The report of Claim 1 1 wherein the total PSA level is greater than or equal to 2.0 ng/ml.

14. The report of Claim 11 wherein the total PSA level is greater than or equal to 4.0 ng/ml.