Serum osteoprotegerin levels are increased in patients with advanced prostate cancer.

PURPOSE: Osteoprotegerin (OPG) is a soluble osteoclastogenesis inhibitor that regulates bone turnover. We reported recently that OPG protein expression is significantly increased in prostate cancer (CaP) cells present in bone metastases. The aim of this study was to determine serum OPG levels in patients at different stages of CaP and correlate the results with disease status. EXPERIMENTAL DESIGN: OPG levels were examined in patients with benign prostatic hyperplasia, clinically localized CaP, early recurrence of CaP, and advanced CaP and evidence of bone metastases. Serum OPG levels were measured by sandwich ELISA assays. The serum Crosslaps (sCTX) assay was used to quantify bone resorption in the advanced CaP group. RESULTS: Serum OPG levels were increased significantly in the advanced CaP group versus all other groups. There was no significant correlation between serum OPG levels and PSA levels either in the advanced CaP group or within any of three treatment subclasses of this group: no Tx, those not treated; Tx, those treated; and R, those treated with resorption blockers. Levels of OPG were negatively correlated with sCTX levels only in the advanced CaP Tx group. sCTX levels correlated with prostate-specific antigen levels in the advanced CaP Tx and R groups but not in the no-Tx group. CONCLUSIONS: Our data show that serum OPG levels are increased with advanced CaP. We hypothesize that OPG levels are related to CaP progression and suggest that further studies of the biological effects of OPG on CaP metastases are warranted.

The percentage of free prostate-specific antigen does not predict extracapsular disease in patients with clinically localized prostate cancer before radical prostatectomy.

OBJECTIVE: To determine whether the percentage of free/total prostate-specific antigen (f/tPSA) can predict the pathological features in patients with clinically localized prostate cancer before radical prostatectomy. PATIENTS AND METHODS: Univariate and multivariate logistic regression was used to analyse data from 171 untreated patients who underwent radical prostatectomy. Variables included the total PSA (tPSA), fPSA, f/tPSA, biopsy Gleason score, clinical stage and patient age. RESULTS: In 115 patients with pathologically organ-confined tumours ( pT2N0) the mean (SD) tPSA value was 6.9 (5.6) ng/mL; in 56 patients with extracapsular disease ( pT3pN0/N+) it was 10.2 (7.6) ng/mL; the respective f/tPSA values were 14.9 (8.1)% and 14.2 (12.9)%. In the univariate and multivariate analysis, tPSA and biopsy Gleason score were highly significant in predicting extracapsular disease (P < 0.001 and 0.002) but the f/tPSA was not (P = 0.18). There was no significant difference between the mean f/tPSA and final Gleason scores. CONCLUSION: The f/tPSA does not predict extracapsular disease in patients with clinically localized prostate cancer before radical prostatectomy. Knowing the f/tPSA provides no significant additional information in predicting extracapsular disease when the biopsy Gleason score and tPSA are known.

Placental bone morphogenetic protein (PLAB) gene expression in normal, pre-malignant and malignant human prostate: relation to tumor development and progression.

The second most common target of prostate-cancer metastasis is bone, and the phenomenon of skeletal metastasis represents the incurable stage of disease. Histologically, skeletal metastasis from prostate cancer is distinctive due to its osteoblastic nature. The osteoblastic bone metastasis shows extensive new bone formation, with possible involvement of the soluble growth factors secreted by tumor cells, such as bone morphogenetic proteins (BMPs). In the present study, we analyzed the gene expression of one of the new members of the BMP family, placental bone morphogenetic protein (PLAB). In situ hybridization studies showed high levels of this gene in normal prostate. However, the gene is down-regulated during the progression of cancer at the primary site. The most significant finding was re-expression of the PLAB gene in osseous metastatic lesions. Our results demonstrate that tumor cells, when released from the primary site and after re-growth elsewhere, are capable of re-expressing specific genes that may play a different role at metastatic sites than at the primary site.

Naturally occurring prostate cancer antigen-specific T cell responses of a Th1 phenotype can be detected in patients with prostate cancer.

BACKGROUND: Cytotoxic T cells (CTL) are considered one of the primary effector cell populations in antitumor immunity. Recent studies, however, have demonstrated the critical importance of helper T cells (Th), specifically interferon gamma (IFN gamma)-secreting Th1 cells, either by supporting an appropriate CTL environment or by recruiting other effector cells. We evaluated whether patients with prostate cancer have naturally occurring Th-cell responses specific for two prostate cancer-associated antigens, prostate-specific antigen (PSA) and prostatic acid phosphatase (PAP), and whether Th1-type responses to these antigens could be detected. METHODS: Peripheral blood mononuclear cells (PBMC) were collected from 80 patients with prostate cancer and 20 male controls without prostate disease. Th-cell responses were evaluated by measuring antigen-specific proliferation. IFN gamma and IL-5 secretion in response to antigen stimulation was determined by enzyme-linked immunosorbent assay. RESULTS: T cell proliferative responses specific for PSA and PAP could be detected in patients with prostate cancer. Six percent (5/80) of patients had T cell responses specific for PSA and 11% (9/80) for PAP. T cell responses specific for PSA were more prevalent in patients with metastatic disease (P = 0.02), whereas responses specific for PAP could be detected in patients irrespective of disease stage. IFN gamma-producing Th cells, specific for both PSA and PAP, could be identified in patients with prostate cancer. CONCLUSIONS: Patients with prostate cancer can have detectable Th-cell responses specific for the prostate cancer-associated proteins PSA and PAP. The presence of antigen-specific Th1 immune responses in prostate cancer patients suggests that an immune environment capable of supporting antigen-specific CTL may exist in vivo. Prostate 47:222-229, 2001.

Experimental models and methods in antibody targeting of renal cell carcinoma.

Metastatic renal cell carcinoma (RCC) is incurable and there are few treatment options that assure even a short prolongation in survival. It is the most common malignancy of the adult kidney and accounts for approximately 12,000 deaths per year (1). Due to a lack of diagnostic markers for early detection and the infrequency of notable symptoms early in the disease process, about one third of patients present with known metastatic disease. However, the staging of RCC is an inaccurate science and in 40% of those patients where a nephrectomy is the treatment choice for presumed organ-confined disease, metastases become evident within about 1 yr (2). For reasons that are poorly understood, metastatic RCC has remained relatively resistant to chemotherapy, biological response modifiers and cellular immunotherapy-although, glimpses of encouragement have appeared in numerous studies. These are discussed in great depth throughout the accompanying chapters.

Antibody immunity to prostate cancer associated antigens can be detected in the serum of patients with prostate cancer.

PURPOSE: Several immune based therapies targeting prostate cancer associated proteins are currently undergoing clinical investigation. In general, however, little is known about the immunogenicity of prostate cancer or which prostate cancer associated proteins elicit immune responses. We determine whether patients with prostate cancer have antibody immunity to known prostate cancer associated proteins, what the prevalence of this immunity is and whether immunity to individual proteins is associated with the stage of disease. MATERIALS AND METHODS: We evaluated the inherent humoral immune response against prostate specific antigen (PSA), prostatic acid phosphatase, p53 and HER-2/neu, all known prostate cancer associated proteins, in 200 patients with various stages of disease and male controls. RESULTS: Antibody immunity to PSA was significantly different between the patient (11%, 22 of 200) and control populations (1.5%, 3 of 100, p = 0.02), and titers 1:100 or greater were particularly prevalent in the subgroup of patients with androgen independent disease (11%, 6 of 56). Antibody immunity to prostatic acid phosphatase and p53 was detected (5.5%, 11 of 200 and 6%, 12 of 200), and was not different from the control population (4%, 4 of 100, p = 0.57 and 7%, 7 of 100, p = 0.74). Antibody immunity to HER-2/neu was significantly higher in patients with prostate cancer (15.5%, 31 of 200) compared to controls (2%, 2 of 100, p = 0.0004), and titers 1:100 or greater were most prevalent in the subgroup of patients with androgen independent disease (16%, 9 of 56). CONCLUSIONS: These findings suggest that prostate cancer is an immunogenic tumor. Moreover, for PSA and HER-2/neu the prevalence of antibody immunity was higher in patients with androgen independent disease, indicating that even patients with advanced stage prostate cancer can have an immune response to their tumor.

Bacterial dna sequences in prostate tissue from patients with prostate cancer and chronic prostatitis.

PURPOSE: Although bacterial genetic material has been detected in prostate tissue from patients with various disorders, the prevalence of these organisms is unknown. We tested the hypothesis that bacterial detection rates differ between patients with prostate cancer and those with the chronic prostatitis/pelvic pain syndrome. MATERIALS AND METHODS: Sterile prostate biopsies were obtained during radical retropubic prostatectomy from 107 patients with prostate cancer and using a perineal approach from 170 with the chronic prostatitis/pelvic pain syndrome. Numerous controls were also evaluated. Bacterial ribosomal encoding DNA (165 rDNA) sequences were detected using a polymerase chain reaction assay. Selected positives were cloned, sequenced and compared with DNA databases. RESULTS: Bacterial DNA sequences were detected in 21 (19. 6%) of 107 patients with prostate cancer compared to 79 (46.4%) of 170 with chronic prostatitis (p <0.0001). These bacteria included urogenital pathogens, other described microorganisms and bacteria not reported previously. CONCLUSIONS: Bacterial DNA sequences may be identified in prostate tissue from many patients. Bacterial detection rates in prostate tissue appear to differ among populations, with higher rates among patients with the chronic prostatitis/pelvic pain syndrome than among those with prostate cancer. Future studies of the role of various bacteria in the prostate may provide insight into the pathophysiology of prostate disease.

Comparison of percent free PSA, PSA density, and age-specific PSA cutoffs for prostate cancer detection and staging.

OBJECTIVES: Various methods have been proposed to increase the specificity of prostate-specific antigen (PSA), including age-specific PSA reference ranges, PSA density (PSAD), and percent free PSA (%fPSA). In this multicenter study, we compared these methods for their utility in cancer detection and their ability to predict pathologic stage after radical prostatectomy in patients with clinically localized, Stage T1c cancer. METHODS: Seven hundred seventy-three men (379 with prostate cancer, 394 with benign prostatic disease), 50 to 75 years old, from seven medical centers were enrolled in this prospective blinded study. All subjects had a palpably benign prostate, PSA 4.0 to 10.0 ng/mL, and a histologically confirmed diagnosis. Hybritech's Tandem PSA and free PSA assays were used. RESULTS: %fPSA and age-specific PSA cutoffs enhanced PSA specificity for cancer detection, but %fPSA maintained significantly higher sensitivities. Age-specific PSA cutoffs missed 20% to 60% of cancers in men older than 60 years of age. %fPSA and PSAD performed equally well for detection (95% sensitivity) if cutoffs of 25% fPSA or 0.078 PSAD were used. The commonly used PSAD cutoff of 0.15 detected only 59% of cancers. %fPSA and PSAD also produced similar results for prediction of the post-radical prostatectomy pathologic stage. Patients with cancer with higher %fPSA values (greater than 15%) or lower PSAD values (0.15 or less) tended to have less aggressive disease. CONCLUSIONS: The results of this study demonstrated that cancer detection (sensitivity) is significantly higher with %fPSA than with age-specific PSA reference ranges. %fPSA and PSAD provide comparable results, suggesting that %fPSA may be used in place of PSAD for biopsy decisions and in algorithms for prediction of less aggressive tumors since the determination of %fPSA does not require ultrasound.

Urodynamic evaluation and long-term results of the orthotopic gastric neobladder in men.

PURPOSE: Orthotopic neobladders are most commonly formed from colon and/or small bowel segments. However, after excellent results were reported in children, we constructed gastric neobladders in select men who had undergone cystectomy. Although gastric neobladders in adults have been reported to have decreased capacity, to our knowledge neither long-term followup nor urodynamic parameters have been reported in these patients. MATERIALS AND METHODS: Gastric neobladder was performed in 8 patients following cystectomy for malignancy in 7 and undiversion in 1. Average followup was 43 months and all patients underwent urodynamic evaluations an average of 9.1 months after surgery. Patients also completed an incontinence questionnaire. The gastric neobladder group was compared to a similar group of patients who underwent neobladder construction from either small bowel (Kock/Hautmann/Studer) or ileocecal segments (Mainz). RESULTS: The gastric neobladder group had significantly reduced mean bladder capacity compared to the ileal or ileocecal neobladder group (309 versus 551 cc, respectively, t = 0.001), while compliance was similarly decreased (27 versus 59 cc/cm. H2O, respectively, t = 0.04). Incontinence rates were greater in the gastric neobladder group (63%) compared to the ileal or ileocecal neobladder group (8% to 23%, t = 0.02). Complication rates were comparable. Revision or removal was required in 3 (38%) patients for severe incontinence, intractable dysuria and ureterogastric anastomotic stricture, respectively. CONCLUSIONS: Adult gastric neobladders as currently constructed are associated with poor urodynamic parameters and high incontinence rates. Routine use of gastric neobladders in adults is not recommended. They may be appropriate, especially as composites, in select cases such as renal failure or inadequate bowel length. The reasons for success in some patients and not in others are unknown.

Probability of prostate cancer detection based on results of a multicenter study using the AxSYM free PSA and total PSA assays.

OBJECTIVES: The determination of the percentage of free prostate-specific antigen (%fPSA) enhances the specificity of prostate cancer (CaP) detection. This study was undertaken to assess the performance of %fPSA in differentiating benign prostate disease from CaP and to determine the CaP probability estimates using the AxSYM Free PSA and AxSYM Total PSA assays. METHODS: In this prospective study, 297 men, 50 years old or older, with a total PSA level between 4 and 10 ng/mL and a nonsuspicious digital rectal examination were enrolled at 10 clinical sites. All subjects underwent at least sextant prostate biopsies to establish the diagnosis. fPSA and total PSA (tPSA) levels were determined using the AxSYM Free PSA and AxSYM Total PSA assays. Percent fPSA values were compared with tPSA values to determine the appropriate cutoffs for prostate biopsy and to calculate the CaP probability estimates. RESULTS: The strongest predictor of CaP in a logistic regression model was %fPSA (odds ratio 2.29), which contributed significantly more than age or tPSA to the predictive model. In this study population, a %fPSA cutoff of 26.4% would have detected 96% of subjects with CaP (sensitivity) and would have eliminated 27.4% of unnecessary biopsies (specificity). CaP probability estimates ranged from 9% to 69% and increased as the %fPSA value decreased. Men with a %fPSA level of 10% or lower had a 69% probability of CaP, and men with a %fPSA level of greater than 26% had a 9% probability of CaP. CONCLUSIONS: Percent fPSA values can help differentiate CaP from benign prostate disease and reduce unnecessary biopsies in 27% of men 50 years old or older whose digital rectal examination was normal and whose tPSA level was between 4 and 10 ng/mL. A %fPSA result can assist the physician and patient in determining the probability of CaP and assessing the need for prostate biopsy.

Differential expression of osteonectin/SPARC during human prostate cancer progression.

The precise mechanism(s) involved in invasion and metastasis of prostate cancer (CaP) is poorly understood. Osteonectin [ON (also known as SPARC or BM-40)] is an antiadhesive protein known to be involved in cell-matrix interactions, migration, and angiogenesis. In this report, we studied the expression of ON in human prostate cell lines, primary tumors, and metastatic foci of CaP. Reverse transcription-PCR and nonradioactive in situ hybridization (ISH) techniques were used to determine ON gene expression. Immunohistochemistry was carried out using the polyclonal antibody LF37 and/or the monoclonal antibody ON-mAb. Low to moderate levels of ON mRNA and protein were observed in glandular epithelial cells of normal tissue as well as a few primary CaPs. However, high levels of ON mRNA and protein were observed in most of the CaP metastatic foci, both osseous and nonosseous. This correlated well with our findings that multiple different CaP cell lines including four CaP cell lines derived from metastases show high levels of ON gene expression. Furthermore, ISH analyses and cell-specific reverse transcription-PCR evaluation showed that both the luminal and basal cells express the ON gene. We conclude that the differential pattern of ON expression suggests that it may play an important role in the progression of CaP.

Percentage of free PSA in black versus white men for detection and staging of prostate cancer: a prospective multicenter clinical trial.

OBJECTIVES: In predominately white populations, measurement of the percentage of free prostate-specific antigen (%fPSA) has been shown to enhance the specificity of total PSA testing for prostate cancer while maintaining high sensitivity and to aid in prostate cancer staging. This study evaluated whether the %fPSA cutoff that maintained a 95% sensitivity in a white population yielded the same sensitivity and specificity in a black population and whether %fPSA was useful in predicting postoperative pathologic features in blacks. METHODS: We evaluated 647 white and 79 black men, prospectively enrolled at prostate cancer screening and surgical referral centers. Subjects were 50 to 75 years old with digital rectal examination findings that were not suspicious for prostate cancer and total PSA values between 4.0 and 10.0 ng/mL. All had undergone needle biopsy of the prostate. Hybritech's Tandem total and free PSA assays were used. RESULTS: Ninety-five percent sensitivity was attained with a %fPSA cutoff of 25% in both races. Use of this cutoff could have avoided unnecessary biopsies in 20% of white and 17% of black subjects (P = 0.69). In receiver operating characteristic (ROC) curve analysis, the area under the curve (AUC) for %fPSA was significantly higher than for total PSA in both blacks (0.76 versus 0.56, P <0.01) and whites (0.70 versus 0.54, P <0.001). In both races, higher %fPSA values indicated a lower risk of cancer and also predicted favorable pathologic features in radical prostatectomy specimens. CONCLUSIONS: A 25% fPSA cutoff detected 95% of cancers and reduced unnecessary biopsies in both races. Higher %fPSA values were associated with favorable postoperative histopathologic findings in both races.

Intermittent androgen suppression in the LuCaP 23.12 prostate cancer xenograft model.

BACKGROUND: Intermittent androgen suppression (IAS) has been proposed as a method of delaying the onset of androgen-independent growth in prostate cancer. While several pilot studies have demonstrated the feasibility of such a treatment, no study to date has defined the effect of IAS on survival. METHODS: We developed an IAS protocol for mice bearing the LuCaP 23.12 human prostate cancer xenograft, with each cycle consisting of 1 week of androgen replacement with a testosterone pellet followed by 3 weeks of androgen withdrawal. Mice that responded to castration with a 40% or greater decrease in serum prostate-specific antigen (PSA) were randomized to treatment with either continuous androgen suppression (CAS) or IAS. Serum PSA, tumor volume, and overall survival were monitored. RESULTS: A total of 75 mice met the randomization criteria. There was no significant difference of survival between animals treated with CAS or IAS (185 vs. 239 days, P = 0.1835). Serum PSA showed evidence of cycling with hormonal manipulation. No cycling was noted in tumor volume. CONCLUSIONS: IAS is not associated with a decrease in survival compared to CAS, yet in patients may offer quality-of-life improvements. Further studies of IAS in the setting of Institutional Review Board (IRB) approved clinical trials should be encouraged. Prostate 43:63-70, 2000. Published 2000 Wiley-Liss, Inc.

NCCN Practice Guidelines for Prostate Cancer.

Systemic therapies for prostate cancer are likely to improve, and as they do, they will have enormous impact on the treatment of high-risk and locally advanced cancers. Further technical improvements in radiotherapy and alternative local modalities, such as cryoablation, are also likely, and will bring even more options for local control. It is certain these guidelines will continue to evolve.

Prediction of post-radical prostatectomy pathological outcome for stage T1c prostate cancer with percent free prostate specific antigen: a prospective multicenter clinical trial.

PURPOSE: Prostate specific antigen (PSA) exists in bound (complexed) and unbound (free) forms in serum. The percentage of free PSA enhances the specificity of PSA testing for prostate cancer detection. We evaluated the use of percent free PSA preoperatively to predict pathological stage. MATERIALS AND METHODS: A total of 379 men with prostate cancer and 394 with benign prostatic disease 50 to 75 years old were enrolled in this prospective study at 7 medical centers. All subjects had a palpably benign prostate gland, serum PSA 4.0 to 10.0 ng./ml. and a histologically confirmed diagnosis. The Hybritech Tandem PSA and free PSA assays were used. Of the 379 cancer patients 268 (71%) underwent radical prostatectomy. RESULTS: Higher percent free PSA levels were associated with more favorable histopathological findings in prostatectomy specimens. A value of 15% free PSA provided the greatest discrimination in predicting favorable pathological outcome. Organ confined cancer, Gleason sum less than 7 and small tumors (10% or less involvement of the prostate) were noted in 75% of patients with greater than 15% and only 34% with 15% or less free PSA (p<0.001). Multivariate logistic regression analysis revealed percent free PSA to be the strongest predictor of postoperative pathological outcome (odds ratio 2.25), followed by biopsy Gleason sum (2.06) and patient age (1.35). Total PSA was not predictive in this cohort but has been shown in prior studies to be predictive of outcome when a broader range of PSA values is evaluated. CONCLUSIONS: Percent free PSA may be used for risk assessment of the presence (diagnosis) and stage of prostate cancer in men with PSA between 4 and 10 ng./ml. Percent free PSA may be combined with PSA, digital rectal examination and biopsy findings to help predict postoperative pathological stage and grade, and may assist the patient and physician in making more informed treatment decisions.

Continence and urodynamic parameters of continent urinary reservoirs: comparison of gastric, ileal, ileocolic, right colon, and sigmoid segments.

OBJECTIVES: To compare the urodynamic parameters and continence rates among five different continent urinary reservoirs. METHODS: Continent urinary reservoirs were constructed in 40 patients with an average age of 60 years (range 23 to 81). Twenty-three had orthotopic neobladders ("neobladders"), and in 17 the reservoirs exited by way of an abdominal wall stoma as "stomal urinary reservoirs." In the neobladders, the detubularized segment was ileum (Hautmann) in 5, ileocecal (Mainz) in 8, sigmoid in 4, and gastric in 6. In the stomal urinary reservoirs, the segment was ileocecal in 11 (Mainz) and right colon in 6 (Indiana). Urodynamic studies were performed at a mean of 9.1 months. RESULTS: Stomal urinary reservoirs had the best continence rates (Indiana pouch 100%, Mainz pouch 91%). Neobladder continence rates were as follows: Hautmann, 80%; Mainz, 75%; sigmoid, 50%; and gastric, 33%. Day and night incontinence rates were nearly identical. Compared with the other pouches, gastric and sigmoid reconstructions had the smallest capacity, were the least compliant, and were the most contractile. CONCLUSIONS: Stomal urinary reservoirs using ileocecal valve and right colon, with or without an overlying patch of ileum, provide similar excellent results. Continence approached 100% in compliant patients without the need for revision. Patients with neobladders were less continent, although those with ileal or ileocecal configurations still had very good continence rates. Neobladders of sigmoid or stomach can be used when necessary, but with greater incontinence rates. This poorer continence can be explained by the decreased capacity, decreased compliance, and a tendency toward high pressure spikes despite detubularization.

Analysis and sorting of prostate cancer cell types by flow cytometry.

BACKGROUND: Prostate tumor heterogeneity as manifested by differential expression of markers can be attributed to multiple types of cancer cells populating a tumor. Does the composition differ between primary tumor and metastasis? How can one isolate the different cancer cell types to study? What is the relationship among cancer cell types? METHODS: Flow cytometry keying on the prostate epithelial cell surface markers CD57 and CD44 was applied to analyze and sort single cells prepared from tumor tissue samples by collagenase digestion. In normal tissue, CD57 is found on luminal cells and CD44 on basal cells. RESULTS: CD57(+) and CD44(+) cells were sorted from various prostate tumor tissue specimens. The CD57(+) cancer cell type was found to predominate in primary tumors, while the CD44(+) cancer cell type was found to predominate in two visceral metastases. All tumors could be characterized by a ratio of CD57(+) and CD44(+) cancer cells. CONCLUSIONS: Two types of prostate cancer cells, CD57(+) and CD44(+), were identified. The finding that most primary tumors contain a predominantly CD57(+) cancer cell population agrees with the argument that cancer cells arise from the transformation of CD57(+) luminal cells. However, CD44(+) cancer cells are also present in some primary tumors; and in some metastases, they, and not CD57(+) cells, constitute a predominant population.

Effects of phenylbutyrate on proliferation and apoptosis in human prostate cancer cells in vitro and in vivo.

Phenylbutyrate (PB) is a potent differentiating agent and currently under investigation for the treatment of prostate cancer (CaP) and other malignancies. We have studied the impact of PB in vitro and in vivo on differentiation, proliferation and apoptosis in the LNCaP and LuCaP 23.1 prostate cancer xenograft models. In vitro we found that i) PB increased PSA secretion/cell, ii) inhibited cell proliferation in a time- and dose-dependent manner resulting in a cell cycle arrest in G1-phase and iii) induced apoptosis at concentrations of 2.5 mM after 3 days of treatment. In PB treated animals tumor growth stabilized or regressed. Combination of castration and PB treatment had a synergistic antiproliferative effect. The growth-inhibitory and differentiating properties and a low toxicity profile of PB provide rationale for further clinical studies in patients with CaP.