Serum levels of bone turnover markers parallel the results of bone scintigraphy in monitoring bone activity of prostate cancer

Bisphosphonates and bone metastases: current status and future directions

Since bone metastases in advanced cancer are common and frequently lead to skeletal-related morbid complications, their treatment remains a major challenge in cancer therapy. Bisphosphonates not only significantly decreased the odds ratios for fracture, need for radiotherapy, and incidence of hypercalcemia, but also had proven ability in the preservation of the 3D microstructure of bone that is responsible for bone stability. Bisphosphonates are well tolerated and have a very low incidence of serious side effects. Consequently, bisphosphonates have become the standard of care for the treatment of malignant bone disease. Benefits of bisphosphonate treatment appears to be more pronounced with longer treatment, indicating that they should be continued until no longer clinically relevant. As this advice has substantial implications on resources, it is essential that the use of bisphosphonates is evidence based.

Current approaches to bone-targeted therapy in genitourinary malignancies

Bone metastases in patients with genitourinary cancers are associated with increased risk for skeletal-related events including pathologic fractures, spinal cord compression, and the requirement for surgery or palliative radiotherapy to bone. The nitrogen-containing bisphosphonate zoledronic acid and the monoclonal antibody against RANK, denosumab, are approved for the prevention of skeletal-related events in genitourinary cancers. These agents have different mechanisms of action and pharmacokinetic profiles, and while both are effective in reducing the risk of skeletal-related events, other clinical effects differ. There is evidence for direct and indirect anticancer activity with zoledronic acid from preclinical studies and emerging data from clinical studies suggesting an effect on patient survival. Potential anticancer mechanisms include inhibition of angiogenesis, enhanced immune surveillance via stimulation of γδ T cells, and reduction of circulating tumor cells. A synergistic effect of chemotherapy plus zoledronic acid has also been suggested. Further research is ongoing regarding the roles of these antiresorptive therapies in patients with bone metastases or at high risk for malignant spread to skeletal sites.

The ZOTECT study: Effect of zoledronic acid on bone metabolism in patients with bone metastases from prostate or breast cancer

Purpose

The ZOTECT study assesses the effect of zoledronic acid (ZOL) on bone-marker levels and potential correlations with disease outcomes in bisphosphonate-naive patients.

Methods

This prospective, single-arm, open-label study in bisphosphonate-naive (≥6 months) patients with bone metastases from prostate cancer (PC; n=301) or breast cancer (BC; n=99) enrolled at 98 German sites (May 2006 to July 2008) investigated the effect of ZOL (4 mg intravenously every 4 weeks×4 months, with a final follow-up at 12 months) on bone-marker levels. Secondary assessments: skeletal-related event (SRE) rate, pain, quality of life (QoL), and prostate-specific antigen levels. Endpoints were assessed using summary statistics by visit/tumor type and Kaplan–Meier analyses.

Results

ZOL treatment significantly decreased bone-marker levels (amino-terminal propeptide of type I collagen [P1NP], C-terminal cross-linking telopeptide of type I collagen [CTX]; P<0.0001), and this decrease was maintained through the final 1-year follow-up visit. Baseline P1NP and CTX levels correlated with extent of bone disease (P<0.0001, each) and on-treatment decreases in marker levels. Skeletal disease burden and bone-marker levels were similar between PC and BC patients, and ZOL did not significantly influence osteoprotegerin/receptor activator of nuclear factor-κB ligand levels. Only 13 SREs occurred in 11 patients, supporting the known ZOL-mediated reduction in SREs. On-treatment bone-marker level changes did not correlate with SRE rate, pain scores, or QoL. Generally, ZOL was well tolerated and adverse events were consistent with its known safety profile.

Conclusions

This study confirms that ZOL therapy significantly reduces bone turnover (measured as P1NP and CTX levels) in patients with bone metastases from PC or BC.

Bone-modifying agents in the treatment of bone metastases in patients with advanced genitourinary malignancies: a focus on zoledronic acid

Many patients with advanced genitourinary malignancies develop bone metastases, which can lead to potentially debilitating skeletal complications. Moreover, age-related bone loss and cancer treatments such as hormonal therapy for prostate cancer can weaken bone, placing patients at risk for osteoporotic fractures in addition to skeletal-related events (SREs) from bone metastases. Zoledronic acid, a bisphosphonate, is approved worldwide to reduce the risk of SREs in patients with bone metastases from solid tumors or bone lesions from multiple myeloma. Zoledronic acid, although underutilized in genitourinary malignancies, has long been the mainstay of treatment in patients with bone metastases, and can also help preserve bone during anticancer therapy. Recently, denosumab, a monoclonal antibody directed against the receptor activator of nuclear factor kappa-B ligand, was approved in the United States and the European Union for reducing the risk of SREs in patients with bone metastases from solid tumors. Denosumab (at a lower dose) is also approved in the European Union and the United States to treat androgen deprivation-induced bone loss in men with prostate cancer. In addition, preclinical rationale and emerging clinical data suggest that bone-modifying agents may be able to delay disease progression in genitourinary cancers, just as newly developed anticancer treatments have produced reductions in SREs, possibly by indirect effects on the disease course. This review article summarizes current data and ongoing studies to preserve bone health in patients with advanced genitourinary cancers.

Bisphosphonates: prevention of bone metastases in prostate cancer

Bone metastases and their associated morbidities are common in patients with advanced prostate cancer and other genitourinary (GU) malignancies. Zoledronic acid> (a bisphosphonate) has long been the mainstay of treatment for reducing the risk of skeletal-related events in patients with bone metastases from GU cancers, and denosumab (a monoclonal antibody directed against the receptor activator of nuclear factor kappa B ligand [RANKL]) has recently received approval for this indication in the United States. Preclinical data indicate that modifying the bone microenvironment may render it less conducive to metastasis, and emerging clinical findings suggest that the potential benefits from bone-directed therapies are not limited to reducing skeletal morbidity-these agents might help to improve survival and delay bone disease progression or even development of bone metastases (if used earlier in the disease course). This chapter reviews the rationale and recent clinical data supporting an antimetastatic role for bone-directed therapies in patients with GU malignancies.

Disseminated prostate cancer cells can instruct hematopoietic stem and progenitor cells to regulate bone phenotype

Prostate cancer metastases and hematopoietic stem cells (HSC) frequently home to the bone marrow, where they compete to occupy the same HSC niche. We have also shown that under conditions of hematopoietic stress, HSCs secrete the bone morphogenetic proteins (BMP)-2 and BMP-6 that drives osteoblastic differentiation from mesenchymal precursors. As it is not known, we examined whether metastatic prostate cancer cells can alter regulation of normal bone formation by HSCs and hematopoietic progenitor cells (HPC). HSC/HPCs isolated from mice bearing nonmetastatic and metastatic tumor cells were isolated and their ability to influence osteoblastic and osteoclastic differentiation was evaluated. When the animals were inoculated with the LNCaP C4-2B cell line, which produces mixed osteoblastic and osteolytic lesions in bone, HPCs, but not HSCs, were able to induced stromal cells to differentiate down an osteoblastic phenotype. Part of the mechanism responsible for this activity was the production of BMP-2. On the other hand, when the animals were implanted with PC3 cells that exhibits predominantly osteolytic lesions in bone, HSCs derived from these animals were capable of directly differentiating into tartrate-resistant acid phosphatase-positive osteoclasts through an interleukin-6-mediated pathway. These studies for the first time identify HSC/HPCs as novel targets for future therapy involved in the bone abnormalities of prostate cancer.

Bone-marker levels in patients with prostate cancer: potential correlations with outcomes

PURPOSE OF REVIEW

The skeleton is typically the first site of metastasis in patients with prostate cancer, and bone metastases can result in severe bone pain and potentially debilitating fractures. Although bone scans are a reliable means of assessing osteoblastic lesions, tools for monitoring early changes in bone health are lacking. Biochemical markers of bone turnover might fulfill this unmet need.

RECENT FINDINGS

Correlative studies have suggested that bone-marker levels may have utility in assessing disease progression and response to bone-directed therapy. Elevated levels of the markers, N-telopeptide of type I collagen and bone-specific alkaline phosphatase, are associated with higher rates of death and skeletal-related events in the bone metastasis setting. Marker levels also correlate with response to zoledronic acid treatment, and similar data with the investigational agent, denosumab, are emerging.

SUMMARY

Changes in bone-marker levels reflect alterations in skeletal homeostasis and can provide important insights into bone disease progression and response to bone-directed therapy in patients with prostate cancer. More mature data from currently ongoing clinical trials will provide further insight on the utility of marker assessments as an adjunct to established monitoring methods in prostate cancer.

Biochemical markers of bone turnover and clinical outcomes in men with prostate cancer

OBJECTIVES

Disrupted skeletal homeostasis is common in patients with prostate cancer. Low bone density is common at diagnosis, and fracture risk is further elevated by the effects of androgen-deprivation therapy. Later in the disease course, bone metastases can result in skeletal morbidity. Although prostate-specific antigen (PSA) levels can provide important insights into overall disease progression, convenient, noninvasive tools for monitoring skeletal health are lacking. Biochemical markers released into serum and urine as a result of bone turnover might fulfill this unmet need. The objectives of this article are to assess current evidence examining the potential utility of bone turnover markers for monitoring skeletal health, bone disease progression, and response to antiresorptive therapies in the prostate cancer setting.

METHODS

Published articles and abstracts from major oncology or urology congresses pertaining to the use of bone turnover markers to monitor skeletal health and disease progression were identified and assessed for relevance and methodologic stringency.

RESULTS

Several randomized trials and correlative studies support the utility of bone marker level changes to assess disease progression in the metastatic setting, bone health during hormonal therapy, and response to bisphosphonate therapy. The available data support potential associations between levels of the collagen type I telopeptides (NTX and CTX) and the severity of metastatic bone disease as well as outcomes during antiresorptive therapy. Evidence linking bone marker level changes with early diagnosis of skeletal metastases is emerging. Although several markers have shown promising results in correlative studies, results from ongoing prospective trials are needed to establish the role of bone markers in this setting.

CONCLUSIONS

Bone marker levels reflect ongoing skeletal metabolism and can provide important insights into bone health and response to bisphosphonate therapy in patients with prostate cancer. The data supporting a role for bone markers to monitor skeletal disease progression and response to zoledronic acid therapy are especially strong. Bone marker assessments may complement established diagnostic and monitoring paradigms in prostate cancer.

The use of molecular markers of bone turnover in the management of patients with metastatic bone disease

Biochemical markers of bone turnover are widely used in clinical practice. These indices have been shown to be associated with the occurrence, prognosis and therapeutic response of malignant bone lesions. For example, markers of bone resorption are often elevated in patients with established bone metastases and while this may point to a role of these markers in the diagnostic workup of cancer patients, the available evidence does not permit any final conclusions as to the accuracy and validity of the presently used markers in the early diagnosis of bone metastases. Many bone turnover markers appear to respond to antiresorptive and antineoplastic therapies, and recent evidence from prospective trials suggests that the aim of bisphosphonate therapy should be to normalize rates of bone remodelling to optimize therapeutic and prognostic outcomes. However, it remains unknown whether the use of bone markers in the routine clinical setting has any defined beneficial effects on overall outcome in cancer patients. Clearly, bone turnover markers have insufficient diagnostic or prognostic value to be used in isolation; however, the combination of these markers with other diagnostic techniques may improve clinical assessment of patients with bone-seeking cancers. This article reviews the available evidence (as of August 2007) on the clinical use of bone turnover markers in the management of patients with metastatic bone disease.

The effect of combined androgen blockade on bone turnover and bone mineral density in men with prostate cancer

Our study and previous reports suggest that castration results in increased bone turnover and lowered BMD and that these changes might be attenuated by anti-androgens, such as BL and EMP.

INTRODUCTION

Recent studies have shown that castration for PC decreases bone mineral density (BMD), while estrogen therapy or bicalutamide (BL) monotherapy maintains BMD. However, the effect of combined androgen blockade (CAB) on bone turnover is not well studied.

METHODS

A total of 204 men were evaluated in the study (control group: n = 56, castration group: n = 102, 'CAB with BL' group: n = 22, 'CAB with estramustine phosphate (EMP)' group: n = 24). We measured steroid hormone levels, BMD (measured at one-third distal radius), bone turnover markers (levels of urinary N-telopeptide cross links of type 1 collagen (u-NTx) and deoxypyridinoline (u-DPD), serum concentrations of osteocalcin (OC)) in order to assess differences between groups.

RESULTS

The BMD % Z score of the castration group was significantly lower than that of the control group or the 'CAB with EMP' group (90.6% vs. 95.5%, 98.6%; p < 0.042, p < 0.044, respectively). Levels of u-NTx, u-DPD, OC of the castration group were the highest followed by the control group, then the 'CAB with BL' group and the 'CAB with EMP' group.

CONCLUSIONS

Our study and previous reports suggests that castration results in increased bone turnover and lowered BMD and that these changes might be attenuated by anti-androgens, such as BL and EMP.

Granulocyte macrophage colony-stimulating factor--secreting allogeneic cellular immunotherapy for hormone-refractory prostate cancer

PURPOSE

This trial evaluated the safety, clinical activity, and immunogenicity of an allogeneic cellular immunotherapy in 55 chemotherapy-naïve patients with hormone-refractory prostate cancer (HRPC). The immunotherapy, based on the GVAX platform, is a combination of two prostate carcinoma cell lines modified with the granulocyte macrophage colony-stimulating factor (GM-CSF) gene.

EXPERIMENTAL DESIGN

HRPC patients with radiologic metastases (n = 34) or rising prostate-specific antigen (PSA) only (n = 21) received a prime dose of 500 million cells and 12 boost doses of either 100 million cells (low dose) or 300 million cells (high dose) biweekly for 6 months. End points were changes in PSA, time to progression, and survival.

RESULTS

Median survival was 26.2 months (95% confidence interval, 17, 36) in the radiologic group: 34.9 months (8, 57) after treatment with the high dose (n = 10) of immunotherapy and 24.0 months (11, 35) with the low dose (n = 24). The median time to bone scan progression in the radiologic group was 5.0 months (2.6, 11.6) with the high dose and 2.8 months (2.8, 5.7) with the low dose. In the rising-PSA group (n = 21) receiving the low dose, the median time to bone scan progression was 5.9 months (5.6, not reached), and median survival was 37.5 months (29, 56). No dose-limiting or autoimmune toxicities were seen; the most common adverse events were injection site reaction and fatigue.

CONCLUSIONS

These results suggest that this GM-CSF-secreting, allogeneic cellular immunotherapy is well tolerated and may have clinical activity in patients with metastatic HRPC. Phase 3 trials to confirm these results are under way.

Plasma osteopontin in comparison with bone markers as indicator of bone metastasis and survival outcome in patients with prostate cancer

BACKGROUND

The study was undertaken to evaluate the diagnostic and prognostic value of plasma osteopontin (OPN) in comparison to bone markers as well as the relationships between the markers and clinico-pathological factors in prostate cancer (PCa) patients.

METHODS

OPN and the bone markers carboxyterminal-telopeptide of type I collagen, bone-specific alkaline phosphatase (bALP), and aminoterminal-propeptide of type I procollagen (PINP) were measured in 90 PCa patients with and without bone metastases, 35 patients with benign prostatic hyperplasia, and 29 healthy men.

RESULTS

OPN and bone markers were significantly elevated in patients with bone metastases compared to the other groups. Significant correlations were found between all four-bone markers (r(s) = 0.43-0.79, all P < 0.01). OPN correlated with tumor grade (r(s) = 0.23, P < 0.05). In receiver-operating characteristics (ROC) analyses, OPN and bone markers were effective in distinguishing PCa patients with and without bone metastases showing areas under the curve (AUC) between 0.80 and 0.88 (all P < 0.001). OPN had an AUC of 0.85 that increased in combination with bALP up to 0.93 providing at the point with the highest diagnostic accuracy both a sensitivity and specificity of about 90%. Kaplan-Meier analyses and Cox proportional hazards regression models showed decreased survival of patients with high OPN and bone marker levels, while only high OPN and PINP were independent negative prognostic factors for PCa-related death.

CONCLUSIONS

OPN alone or in combination with bone markers is useful as diagnostic marker in the detection of bone metastases and as prognosticator in the survival prediction in PCa patients.

Targeting factors involved in bone remodeling as treatment strategies in prostate cancer bone metastasis

Prostate cancer is the most commonly diagnosed cancer in men within the western world and the third leading cause of cancer-related deaths. Even if the cancer is considered localized to the prostate, there is a 15% to 20% incidence of subsequent metastatic disease. Prostate cancer has a very high proclivity for metastasizing to bone, with approximately 90% of men with advanced disease having skeletal lesions. The prostate cancer metastases are characteristically osteoblastic, with extensive new bone deposition, unlike other tumors that metastasize to bone and cause an osteolytic response reflective of bone degradation. There are a considerable number of studies relating to inhibition of the osteoblastic response, including interference with endothelin-1, bone morphogenetic proteins, and Wnt signaling pathways. Within the past few years, several studies showed that increased osteolytic activity also occurs in the background of the prostate cancer skeletal metastases. Because growth factors are being released from the bone matrix during degradation, it suggests that inhibition of osteolysis might be effective in slowing tumor growth. Several strategies are being developed and applied to affect directly the osteolytic events, including use of bisphosphonates and targeting the critical biological regulators of osteoclastogenesis, receptor activator of nuclear factor-kappaB and receptor activator of nuclear factor-kappaB ligand. This review focuses on several of the clinical and preclinical strategies to inhibit the growth of prostate cancer cells in bone and to alleviate the multitude of associated skeletal-related events.

Diagnosis of Bone Metastasis in Men with Prostate Cancer by Measurement of Serum ICTP in Combination with Alkali Phosphatase and Prostate-specific Antigen

AIMS

Carboxy-terminal telopeptide of type I collagen (ICTP) is a parameter of bone absorption, and has recently been introduced to monitor bone metastases. The aim of this retrospective study was to investigate the potential of ICTP as a candidate serum marker of bone metastasis in prostate cancer.

MATERIALS AND METHODS

Serum markers in 155 men pathologically diagnosed with prostate cancer were measured. The serum levels of ICTP, prostate-specific antigen (PSA), and alkali phosphatase (ALP) were compared to assess the extent of disease (EOD) scores from bone scans and then analysed statistically.

RESULTS

The serum ICTP levels were not well correlated with the EOD scores in the total group of men, men newly diagnosed with prostate cancer, or men previously diagnosed with prostate cancer who were followed up. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of ICTP (cut-off value, 5.0 ng/ ml) of the men newly diagnosed with prostate cancer were 78.6%, 88.0%, 78.6%, and 88.0%, respectively. In these men, the specificity and PPV of ALP (cut-off value, 335 IU/l) were 100%, whereas the sensitivity and NPV of PSA (cut-off value, 40 ng/ml) were 100% in this study. The serum levels of ICTP in the men with low ALP (< 335 IU/l) and high PSA (> or = 40 ng/ ml) clearly separated the men with or without bone metastasis, as judged by bone scans.

CONCLUSION

We found that the ICTP is not a superior serum marker for bone metastases compared with ALP or PSA. Our study suggests, however, that the ICTP measurement is useful in a certain subset of men with the combination of PSA and ALP in distinguishing men with bone metastasis from those without.

Bone markers and current laboratory assays

Metastasis of cancer to bone leads to significant alterations in normal bone remodelling that are reflected in changes in bone turnover markers. These markers are classically defined as markers of bone resorption or formation; markers of bone resorption are measures of osteoclastic activity, whereas markers of bone formation are measures of osteoblastic activity. Recently, there has been growing interest in the use of these markers in metastatic bone disease (MBD), and an increasing number of studies have investigated the potential use of these markers in diagnosis, monitoring of disease progression and treatment, and prediction of outcome. In this review, we briefly discuss the biology of bone metastases as well as describe the bone turnover markers and their possible role in aiding clinicians in the treatment of patients with MBD.

Clinical use of markers of bone turnover in metastatic bone disease

Bone metastases profoundly perturb normal bone remodeling. Biochemical markers of bone turnover have been shown to reflect these tumor-induced changes in bone remodeling and might therefore be useful in the diagnosis and follow-up of patients with malignant bone disease. Most markers of bone turnover, particularly those of bone resorption, are elevated in patients with established bone metastases. While this might indicate a role for bone markers as diagnostic tools in cancer patients, the available evidence does not provide any final conclusions as to the accuracy and validity of the markers presently used in the early diagnosis of bone metastases. Markers of bone resorption respond promptly and profoundly to bisphosphonate and antineoplastic therapy, and this response is associated with a favorable clinical outcome. Most markers, however, have been more useful in groups of patients monitored in clinical studies than in studies of individuals. While this makes them a good tool for drug development, it remains unknown whether the use of bone markers in a routine clinical setting has any defined beneficial effects on overall outcome in cancer patients. In particular, no study has addressed the question of whether patients with bone metastases should be treated according to their rate of bone turnover and what the treatment goals are in this respect. While it is unlikely that bone-turnover markers have sufficient diagnostic or prognostic value when used in isolation, the combination of these markers with other diagnostic techniques might be the way forward to improve the clinical assessment of patients with cancers of the bone.

Assessment of therapeutic response in patients with metastatic bone disease

Metastatic bone disease is common in cancer patients and causes substantial disease-related morbidity and mortality. However, several effective treatments are available for the management of these patients. Bisphosphonates, which inhibit osteoclast-mediated resorption of bone matrix, are especially important because they decrease the incidence of skeletal-related events in many tumour types and can complement antineoplastic therapies. At present, assessment of treatment for bone metastases is hindered by a lack of effective, rapid methods to measure disease response. We discuss the difficulties of current measures of response assessment and describe the development of new radiological and biochemical markers of bone metastases. Assays that detect type I collagen telopeptides as markers of bone resorption seem to be most promising at present.

Comparison of 10 serum bone turnover markers in prostate carcinoma patients with bone metastatic spread: diagnostic and prognostic implications

Our aim was to assess the diagnostic accuracy of bone markers in serum of patients with prostate cancer (PCa) for early detection of bone metastases and their usefulness as predictors of PCa-caused mortality. In sera of 117 PCa patients (pN0M0, n = 39; pN1M0, n = 34; M1, n = 44), 35 healthy men and 35 patients with benign prostatic hyperplasia, bone formation markers [total and bone-specific alkaline phosphatase (tALP, bALP), amino-terminal procollagen propeptides of type I collagen (P1NP), osteocalcin (OC)], bone resorption markers [bone sialoprotein (BSP), cross-linked C-terminal (CTX) and cross-linked N-terminal (NTX) telopeptides of type I collagen, tartrate-resistant acid phosphatase isoenzyme 5b (TRAP)] and osteoclastogenesis markers [osteoprotegerin (OPG), receptor activator of nuclear factor kappaB ligand (RANKL)] were measured. tALP, bALP, BSP, P1NP, TRAP, NTX and OPG were significantly increased in PCa patients with bone metastases compared to patients without metastases. OPG showed the best discriminatory power to differentiate between these patients. Logistic regression analysis resulted in a model with OPG and TRAP as variables that predicted bone metastasis with an overall correct classification of 93%. Patients with concentrations of OPG, P1NP, tALP, bALP, BSP, NTX, TRAP and CTX above cut-off levels showed significantly shorter survival than patients with low marker concentrations. Multivariate Cox proportional hazards regression revealed that only OPG and BSP were independent prognostic factors for PCa-related death. Thus, the importance of serum OPG in detecting bone metastatic spread, alone or in combination with other bone markers, and predicting survival in PCa patients has been clearly demonstrated.

Immunological monitoring during combination of patient-oriented peptide vaccination and estramustine phosphate in patients with metastatic hormone refractory prostate cancer

BACKGROUND

Additive antitumor effects could be achieved by combination of immunotherapy and cytotoxic agents with no or minimum suppression.

METHODS

Thirteen patients positive for human leukocyte antigen (HLA)-A24 or -A2 with metastatic hormone refractory prostate cancer (HRPC) who had failed to respond to the prior-peptide vaccination were entered in the combined peptide vaccination and estramustine phosphate. Conducted immune monitoring on those 13 patients were mainly peptide-specific cytotoxic T lymphocyte (CTL) precursor analysis by IFN-gamma productions and peptide-reactive IgG by an enzyme-linked immunosorbent assay (ELISA).

RESULTS

Grade 3 arrhythmia or cerebral infarction was observed in two cases, and Grade 1 or 2 dermatologic reaction at the vaccination sites was observed in all 13 cases. Eleven patients who received more than one cycle of treatment were eligible for immunological and clinical evaluation. There was no significant immunosuppression in most cases when the peptide and a half dose (280 mg/day) of estramustine were administrated, whereas severe immunosuppression was observed in the first two patients who received both the peptide and a full dose (560 mg/day) estramustine. Augmentation of peptide-specific CTL precursors or peptide-specific IgG was observed in 6 of 11 or 10 of 11 cases, respectively. Ten of 11 patients showed serum prostate-specific antigen (PSA) level decrease from the baseline including 8 patients with a serum PSA level decrease of > or =50%.

CONCLUSIONS

These results encouraged the further evaluation of the combination of peptide vaccination and low-dose estramustine phosphate for metastatic HRPC patients.