Timothy L. Ratliff

Measurement of prostate-specific antigen in serum as a screening test for prostate cancer

BACKGROUND Prostate-specific antigen (PSA) is secreted exclusively by prostatic epithelial cells, and its serum concentration is increased in men with prostatic disease, including cancer. We evaluated its usefulness in the detection and staging of prostate cancer. METHODS We measured serum PSA concentrations in 1653 healthy men 50 or more years old. Those with PSA values greater than or equal to 4.0 micrograms per liter then underwent rectal examination and prostatic ultrasonography. Ultrasound-directed prostatic needle biopsies were performed in the men with abnormal findings on rectal examination, ultrasonography, or both. The results were compared with those in 300 consecutively studied men 50 or more years old who underwent ultrasound-directed biopsy because of symptoms or abnormal findings on rectal examination. RESULTS Serum PSA levels ranged from 4.0 to 9.9 micrograms per liter in 6.5 percent of the 1653 men (107). Nineteen of the 85 men in this group (22 percent) who had prostatic biopsies had prostate cancer. Serum PSA levels were 10.0 micrograms per liter or higher in 1.8 percent of the 1653 men (30). Eighteen of the 27 men in this group (67 percent) who had prostatic biopsies had cancer. If rectal examination alone had been used to screen the men who had biopsies, 12 of the 37 cancers (32 percent) would have been missed. If ultrasonography alone had been used to screen these men, 16 of the 37 cancers (43 percent) would have been missed. Serum PSA measurement had the lowest error rate of the tests, and PSA measurement plus rectal examination had the lowest error rate of the two-test combinations. CONCLUSIONS The combination of measurement of the serum PSA concentration and rectal examination, with ultrasonography performed in patients with abnormal findings, provides a better method of detecting prostate cancer than rectal examination alone.

Comparison of Digital Rectal Examination and Serum Prostate Specific Antigen in the Early Detection of Prostate Cancer: Results of a Multicenter Clinical Trial of 6,630 Men

&NA; To compare the efficacy of digital rectal examination and serum prostate specific antigen (PSA) in the early detection of prostate cancer, we conducted a prospective clinical trial at 6 university centers of 6,630 male volunteers 50 years old or older who underwent PSA determination (Hybritech Tandom‐E or Tandem‐R assays) and digital rectal examination. Quadrant biopsies were performed if the PSA level was greater than 4 &mgr;g./l. or digital rectal examination was suspicious, even if transrectal ultrasonography revealed no areas suspicious for cancer. The results showed that 15% of the men had a PSA level of greater than 4 &mgr;g./l., 15% had a suspicious digital rectal examination and 26% had suspicious findings on either or both tests. Of 1,167 biopsies performed cancer was detected in 264. PSA detected significantly more tumors (82%, 216 of 264 cancers) than digital rectal examination (55%, 146 of 264, p = 0.001). The cancer detection rate was 3.2% for digital rectal examination, 4.6% for PSA and 5.8% for the 2 methods combined. Positive predictive value was 32% for PSA and 21% for digital rectal examination. Of 160 patients who underwent radical prostatectomy and pathological staging 114 (71%) had organ confined cancer: PSA detected 85 (75%) and digital rectal examination detected 64 (56%, p = 0.003). Use of the 2 methods in combination increased detection of organ confined disease by 78% (50 of 64 cases) over digital rectal examination alone. If the performance of a biopsy would have required suspicious transrectal ultrasonography findings, nearly 40% of the tumors would have been missed. We conclude that the use of PSA in conjunction with digital rectal examination enhances early prostate cancer detection. Prostatic biopsy should be considered if either the PSA level is greater than 4 &mgr;g./l. or digital rectal examination is suspicious for cancer, even in the absence of abnormal transrectal ultrasonography findings.

Effect of Inflammation and Benign Prostatic Hyperplasia on Elevated Serum Prostate Specific Antigen Levels

PURPOSE We quantify the causes of elevated serum prostate specific antigen (PSA) concentrations in men whose prostate biopsies repeatedly showed no cancer. MATERIALS AND METHODS The effects of prostate volume, inflammation, echogenicity on ultrasound and calculi were examined in a large PSA-based screening population of 148 men with serum PSA concentrations greater than 4.0 ng./ml., findings suspicious for cancer on digital rectal examination and multiple negative biopsies. These men were selected and compared to 64 men with suspicious rectal examinations, multiple negative biopsies and serum PSA concentrations of 4.0 ng./ml. or less. RESULTS The high PSA group had larger prostates (68 versus 33 cc, p = 0.0001) and significantly more subclinical prostatic inflammation. Acute and chronic inflammation was more prevalent in the high PSA group (63% versus 27%, p = 0.0001 and 99% versus 77%, p = 0.0001, respectively). A simultaneous regression analysis showed that prostatic size accounted for 23%, inflammation 7%, prostatic calculi 3% and nonisoechoic ultrasound lesions 1% of the serum PSA variance. CONCLUSIONS Prostate volume and inflammation are the most important factors contributing to serum PSA elevation in men without clinically detectable prostate cancer.

Selection of optimal prostate specific antigen cutoffs for early detection of prostate cancer: receiver operating characteristic curves.

A prospective clinical trial of prostate cancer screening was conducted at 6 university centers including 6,630 men 50 years old or older who underwent a serum prostate specific antigen (PSA) determination and digital rectal examination. Biopsies were performed if the PSA level was greater than 4.0 ng./ml. (Hybritech Tandem assay) or digital rectal examination was suspicious for cancer. We evaluated the effect on biopsy rate and cancer detection if the cutoff value was shifted from 4.0 to age-specific reference ranges recommended in the literature. In men 50 to 59 years old with normal digital rectal examination findings a decrease from 4.0 to 3.5 ng./ml. would have resulted in a 45% increase in the number of biopsies (39 of 87) and a projected 15% increase in cancer detection. An increase from 4.0 to 4.5 ng./ml. in men 60 to 69 years old would result in 15% fewer biopsies (35 of 238) and would miss 8% of the organ confined tumors (2 of 25). Increasing the cutoff to 6.5 ng./ml. in men 70 years old or older would result in 44% fewer biopsies (70 of 159) and would miss 47% of the organ confined cancers (7 of 15). The number of biopsies performed for each cancer detected with a PSA level of greater than 4.0 ng./ml. remains constant across age groupings, which suggests that the cutoff of 4.0 ng./ml. does not need to be altered in the older men, since it is apparently unaffected by the simultaneously increasing prevalence of benign prostatic hyperplasia and cancer with age. We conclude that a serum PSA concentration of 4.0 ng./ml. should be used as a general guideline for biopsy in all age groups.

Platelet-Mediated Modulation of Adaptive Immunity: A Communication Link between Innate and Adaptive Immune Compartments

Platelets are highly reactive components of the circulatory system with well-documented hemostatic function. Recent studies extend platelet function to modulation of local inflammatory events through the release of chemokines, cytokines, and a number of immunomodulatory ligands, including CD154. We hypothesized that platelet-derived CD154 modulates adaptive immunity. The data reported herein demonstrate that platelets, via CD154, induce dendritic cell maturation, B cell isotype switching, and augment CD8(+) T cell responses both in vitro and in vivo. Platelet transfusion studies demonstrate that platelet-derived CD154 alone is sufficient to induce isotype switching and augment T lymphocyte function during viral infection, leading to enhanced protection against viral rechallenge. Additionally, depletion of platelets in normal mice results in decreased antigen-specific antibody production.

Risks and Benefits of Repeated Courses of Intravesical Bacillus Calmette-guerin Therapy for Superficial Bladder Cancer

An actuarial analysis of the risks and benefits of repeated courses of intravesical bacillus Calmette-Guerin therapy for superficial bladder cancer was performed for 100 consecutive patients treated for carcinoma in situ (29), prophylaxis against recurrent tumor (51) or residual superficial papillary tumor (21). The risk-to-benefit ratio at entry into bacillus Calmette-Guerin therapy (7 per cent risk of invasive cancer developing, 5 per cent risk of metastases and 77 per cent prospect for status free of tumor) and in patients who had failed only 1 course of bacillus Calmette-Guerin therapy (11 per cent invasive cancer, 14 per cent metastases and 58 per cent free of tumor) were highly favorable. However, among patients who had failed 2 or more courses of bacillus Calmette-Guerin therapy the risks of invasive (30 per cent) or metastatic (50 per cent) cancer developing exceeded the prospects for eradicating the superficial tumor present (20 per cent) with further therapy. The results suggest that patients who have failed 2 courses of bacillus Calmette-Guerin therapy (as given in our treatment protocol) should be considered for alternative treatment.

Comparison of Prostate Specific Antigen Concentration Versus Prostate Specific Antigen Density in the Early Detection of Prostate Cancer: Receiver Operating Characteristic Curves

We present the results of a prospective multicenter clinical trial of nearly 5,000 men in which prostate specific antigen (PSA) density was compared to the serum PSA concentration alone for early detection of prostate cancer. All men were evaluated with PSA and digital rectal examination. If PSA was elevated (greater than 4 ng./ml., Hybritech Tandem assay) or digital rectal examination was suspicious, transrectal ultrasound guided biopsies were recommended. Prostate volume was estimated by transrectal ultrasound measurements using a prolate ellipse volume calculation and PSA density was calculated by dividing serum PSA concentration by gland volume. Using a PSA density cutoff of 0.15 as recommended in the literature enhanced specificity but at the cost of missing half of the tumors. Of the organ confined neoplasms 47% were detected by a PSA of greater than 4.0 ng./ml. but they were missed by a PSA density of more than 0.15. PSA density may not be predictive for cancer because accurate estimation of transrectal ultrasound volume is difficult (r = 0.61 for estimated transrectal ultrasound volume versus pathological prostate weight). However, a relationship does exist among transrectal ultrasound volume, PSA and positive predictive value for cancer. PSA concentrations of less than 4.0 ng./ml. did not indicate a need for biopsy (positive predictive value 12 to 17%) unless the digital rectal examination findings were suspicious for cancer. A high percentage of patients with a PSA of more than 10 ng./ml. had cancer (30 to 75%), regardless of gland size. Patients with intermediate PSA concentrations (4.1 to 9.9 ng./ml.) and a gland size of 50 cc or less had a 35 to 51% positive predictive value, while those with intermediate PSA concentrations and a large gland (more than 50 cc) had a 15% positive predictive value. We conclude that in men with a PSA level of 4.1 to 9.9 ng./ml., and normal digital rectal examination and transrectal ultrasound findings, the use of a PSA density cutoff of more than 0.15 for biopsy results in half of the tumors being missed. Thus, we recommend that men in this group undergo biopsy based upon serum PSA concentration rather than PSA density.

T-Cell Subsets Required for Intravesical BCG Immunotherapy for Bladder Cancer

Intravesical bacille Calmette-Guérin (BCG) has been shown in prospective randomized clinical trials to be the treatment of choice for superficial bladder cancer. In this investigation we evaluated the role of CD4 and CD8 lymphocytes in the antitumor response. Monoclonal antibodies to thy 1.2, CD8, CD4 and an isotype control were injected intravenously to deplete T cell populations. After depletion (verified by flow cytometry), BCG therapy was initiated. The results demonstrate that the depletion of either CD4 or CD8 T cell subsets eliminated BCG-mediated antitumor activity. Footpad delayed type hypersensitivity (DTH) was aborted only in CD4 depleted mice; it was essentially unchanged in CD8 depleted mice. However, the presence of DTH was not sufficient for induction of BCG-mediated antitumor activity. Exogenous IL-2 at levels sufficient to induce lymphokine activated killer cell activity did not substitute for CD4 cells. There was no evidence for the induction of protective immunity to the tumor after BCG therapy. These results demonstrate the requirement for T lymphocytes in BCG-mediated antitumor activity and further demonstrate that the presence of both CD4 and CD8 subsets are required. CD8 depletion experiments suggest that the presence of CD4-mediated DTH is not sufficient for the induction of antitumor activity. Furthermore, these data suggest that BCG-mediated antitumor activity is a localized phenomenon that does not induce protective immunity.

Adenoviral-mediated transfer of the TNF-related apoptosis-inducing ligand/Apo-2 ligand gene induces tumor cell apoptosis.

TNF-related apoptosis-inducing ligand (TRAIL) is a member of the TNF superfamily of cytokines that induces apoptosis in a variety of cancer cells. The results presented in this study demonstrate that introduction of the human TRAIL gene into TRAIL-sensitive tumor cells using an adenoviral vector leads to the rapid production and expression of TRAIL protein, and subsequent death of the tumor cells. Tumor cell death was mediated by an apoptotic mechanism, as evidenced by the activation of caspase-8, cleavage of poly(ADP-ribose) polymerase, binding of annexin V, and inhibition by caspase inhibitor zVAD-fmk. These results define a novel method of using TRAIL as an antitumor therapeutic, and suggest the potential use for an adenovirus-encoding TRAIL as a method of gene therapy for numerous cancer types in vivo.

Requirement of a Thymus Dependent Immune Response for Bcg-mediated Antitumor Activity

Surgical adjuvant intravesical bacille Calmette-Guerin (BCG) therapy is an effective method of treating superficial transitional cell carcinoma of the bladder. The role of the immune response in the antitumor activity of intravesical BCG is not known. We investigated the requirement of a thymus-dependent immune response for the inhibition of the growth of the intravesically implanted mouse bladder tumor, MBT-2. Intravesical BCG had no antitumor activity when administered to athymic nude mice bearing MBT-2 tumors. In two experiments tumor outgrowth in control and BCG-treated mice was identical. Adoptive transfer of BCG sensitized splenocytes (one spleen equivalent per mouse injected intravenously immediately prior to the first BCG treatment) syngeneic to the MBT-2 tumor transferred delayed hypersensitivity reactivity to BCG antigens and restored the antitumor activity of intravesical BCG. In two separate experiments mice receiving splenocytes plus BCG had 0 and 20% tumor outgrowth compared with 100% in control mice (p less than .02 and p less than .05, respectively). These results demonstrate that the antitumor activity of intravesical BCG therapy requires a thymus-dependent immune response.