METABOLIC BONE DISEASE INDUCED BY PROSTATE CANCER: RATIONALE FOR THE USE OF BISPHOSPHONATES

Prostate cancer bone metastases biology and clinical management (Review)

Prostate cancer (PCa) is one of the most prominent causes of cancer-related mortality in the male population. A highly impactful prognostic factor for patients diagnosed with PCa is the presence or absence of bone metastases. The formation of secondary tumours at the bone is the most commonly observed site for the establishment of PCa metastases and is associated with reduced survival of patients in addition to a cohort of life-debilitating symptoms, including mobility issues and chronic pain. Despite the prevalence of this disease presentation and the high medical relevance of bone metastases, the mechanisms underlying the formation of metastases to the bone and the understanding of what drives the osteotropism exhibited by prostate tumours remain to be fully elucidated. This lack of in-depth understanding manifests in limited effective treatment options for patients with advanced metastatic PCa and culminates in the low rate of survival observed for this sub-set of patients. The present review aims to summarise the most recent promising advances in the understanding of how and why prostate tumours metastasise to the bone, with the ultimate aim of highlighting novel treatment and prognostic targets, which may provide the opportunity to improve the diagnosis and treatment of patients with PCa with bone metastases.

Bisphosphonates in Oncology: Physiopathologic Bases and Clinical Activity

Osteoclastic activation is the ultimate way of bone resorption in neoplasia, induced by the combined effects of tumor-secreted humoral factors (especially parathyroid hormone-related peptides) and osteoclastic-osteoblastic interaction. Bisphosphonates inhibit the osteoclast activity and reduce bone resorption and are a valuable supportive measure for bone disease of neoplasms. Experimental models also suggest an activity of bisphosphonates against cancer cells. Controlled studies, especially in advanced breast cancer and multiple myeloma, indicate different effectiveness against the distinct skeletal-related events. Intravenous clodronate and, especially, pamidronate and zoledronate are the first-choice drugs for hypercalcemia, and they play a significant role in reducing metastatic bone pain. Their prolonged use delays, without hampering, the progression of bone disease, including the appearance of osteolysis and the occurrence of pathologic fractures. This effect is probably more valuable when bisphosphonates are administered early in the course of the disease. The evidence that adjuvant bisphosphonates improve survival needs to be confirmed in ongoing studies. Although poorly absorbed by the gastrointestinal tract, oral bisphosphonates are effective in preventing and treating cancer-induced osteoporosis in long-living patients with operable breast cancer. At present, there is little hope that newer bisphosphonates are more effective than those currently used.

Metabolic Effects of Single-Dose Pamidronate Administration in Prostate Cancer Patients with Bone Metastases

Background

Increased osteolysis usually accompanies sclerotic bone metastases from prostate cancer. This provides a rationale for the use of bisphosphonates to treat bone pain and prevent skeletal complications.

Methods

The fasting urinary levels of calcium, hydroxyproline (OHPRO), pyridinolines (PYD), deoxypyridinolines (DPYD), collagen cross-linked N-telopeptide (NTX) and the serum values of calcium, total alkaline phosphatase and relevant bone isoenzyme, bone gla protein (BGP), carboxy-telopeptide of type I collagen (ICTP) and parathyroid hormone (PTH) were determined at baseline and on the 15th, 30th, 60th and 90th days after single-dose (90 mg) pamidronate administration in 35 consecutive prostate cancer patients with bone metastases. These biochemical indices and serum interleukin 6 (IL-6) were also measured after four days in the last consecutive 17 cases.

Results

PYD, DPYD and NTX showed a significant decrease lasting four weeks (p<0.01, <0.01 and <0.001, respectively). OHPRO and ICTP did not change significantly. The NTX decline was greater than that of PYD and DPYD (maximum percent decrease: −71.3, −23.1 and −28.2, respectively). Bone formation markers and serum calcium did not change significantly. Serum PTH showed a rapid initial increase followed by a slow decrease (p<0.001). DPYD and NTX patterns did not correlate with changes in bone pain. As observed in the last 17 cases, the maximum osteolysis inhibition after pamidronate occurred on the fourth day after drug infusion. Serum IL-6 levels showed a short-lived decrease preceded by a transient rise on the fourth day.

Conclusions

Pamidronate is able to induce a decrease in bone resorption without significantly influencing bone formation. The maximum decrease in bone resorption occurs very early. NTX is the most sensitive bone resorption marker in bisphosphonate therapy monitoring. Changes in IL-6 but not bone resorption markers may be useful in the prediction of symptomatic response.

Low dose effect of bisphosphonates on hMSCs osteogenic response to titanium surface in vitro

Since the 1980s, titanium (Ti) implants have been routinely used to replace missing teeth. This success is mainly due to the good biocompatibility of Ti and the phenomenon of osseointegration, with very early events at implant placement being important in determining good osseointegration. However, enhancing implant performance with coatings such as hydroxyapatite (HA) and calcium phosphate has proved largely unsuccessful. Human mesenchymal stem cells (hMSCs) are the first osteogenic cells to colonise implant surfaces and offer a target for enhancing osseointegration. We previously reported that small doses of bisphosphonate (BP) may play an integral role in enhancing hMSC proliferation and osteogenic differentiation. The aim of this study is to investigate whether small doses of bisphosphonates enhance proliferation and osteogenic differentiation of hMSCs on Ti surfaces, to enhance bone osseointegration and to accelerate wound healing around the implant surface. Our data suggests that treating cells with small doses of BP (100 nM & 10 nM) induces significant hMSC stimulation of osteogenic markers including calcium, collagen type I and ALP compared to control group on titanium surfaces (P < 0.05). In addition, cell proliferation and migration were significantly enhanced on titanium surfaces (P < 0.05).

Interleukin-27 gene delivery for modifying malignant interactions between prostate tumor and bone

We have examined the role of a novel cytokine, interleukin-27 (IL-27), in mediating interactions between prostate cancer and bone. IL-27 is the most recently characterized member of the family of heterodimeric IL-12-related cytokines and has shown promise in halting tumor growth and mediating tumor regression in several cancer models, including prostate cancer. Prostate cancer is frequently associated with metastases to the bone, where the tumor induces a vicious cycle of communication with osteoblasts and osteoclasts to induce bone lesions, which are a significant cause of pain and skeletal-related events for patients, including a high fracture risk. We describe our findings in the effects of IL-27 gene delivery on prostate cancer cells, osteoblasts, and osteoclasts at different stages of differentiation. We applied the IL-27 gene delivery protocol in vivo utilizing sonoporation (sonodelivery) with the goal of treating and reducing the growth of prostate cancer at a bone metastatic site in vivo. We used a new model of immune-competent prostate adenocarcinoma and characterized the tumor growth reduction, gene expression, and effector cellular profiles. Our results suggest that IL-27 can be effective in reducing tumor growth, can help normalize bone structure, and can promote enhanced accumulation of effector cells in prostate tumors. These results are promising, because they are relevant to developing a novel IL-27-based strategy that can treat both the tumor and the bone, by using this simple and effective sonodelivery method for treating prostate tumor bone metastases.

Interleukin-27 expression modifies prostate cancer cell crosstalk with bone and immune cells in vitro

Prostate cancer is frequently associated with bone metastases, where the crosstalk between tumor cells and key cells of the bone microenvironment (osteoblasts, osteoclasts, immune cells) amplifies tumor growth. We have explored the potential of a novel cytokine, interleukin-27 (IL-27), for inhibiting this malignant crosstalk, and have examined the effect of autocrine IL-27 on prostate cancer cell gene expression, as well as the effect of paracrine IL-27 on gene expression in bone and T cells. In prostate tumor cells, IL-27 upregulated genes related to its signaling pathway while downregulating malignancy-related receptors and cytokine genes involved in gp130 signaling, as well as several protease genes. In both undifferentiated and differentiated osteoblasts, IL-27 modulated upregulation of genes related to its own signaling pathway as well as pro-osteogenic genes. In osteoclasts, IL-27 downregulated several genes typically involved in malignancy and also downregulated osteoclastogenesis-related genes. Furthermore, an osteogenesis-focused real-time PCR array revealed a more extensive profile of pro-osteogenic gene changes in both osteoblasts and osteoclasts. In T-lymphocyte cells, IL-27 upregulated several activation-related genes and also genes related to the IL-27 signaling pathway and downregulated several genes that could modulate osteoclastogenesis. Overall, our results suggest that IL-27 may be able to modify interactions between prostate tumor and bone microenvironment cells and thus could be used as a multifunctional therapeutic for restoring bone homeostasis while treating metastatic prostate tumors.

[Use of zoledronic acid in patients with prostate cancer bone metastases: control of pain and musculoskeletal complications]

Background. Patients suffering from prostatic carcinoma are at high risk of having bone complications because of the metastatic progression of the disease to the skeleton and the consequences of androgenic deprivation. Zoledronic acid is a potent inhibitor of the bone resorption mediated by the osteoclasts, and is the only bisphosphonate whose capacity of reducing significantly the skeleton morbidity in patients with bone metastases is statistically proved. Methods. To attest tolerability and efficacy of zoledronic acid in preventing unfavorable skeletal events and in reducing osteomuscular pain, 25 patients - aged 75 years, suffering from hormone-responsive prostatic carcinoma under hormonal therapy with bone metastases, have been followed and subjected to IV monthly infusion of 4 mg zoledronic acid for 12 consecutive months, associated to daily intake of calcium and multivitamin supplementations. Results. At the end of the study, a sensible improvement in their clinical conditions and in their perception of the pain has been recorded in 23 patients and valued through a set of questions (Brief Pain Inventory). Conclusions. Zoledronic acid is therefore confirmed to be an effective medicine in preventing the skeleton complications and in controlling the painful symptoms in patients suffering from prostatic carcinoma with bone metastases.

Potential pathophysiological mechanisms in osteonecrosis of the jaw

Bisphosphonates are used in the treatment of hypercalcemia of malignancy, skeletal complications associated with metastastic bone disease, Paget's disease, and osteoporosis. Osteonecrosis of the jaw (ONJ) is a recently described clinical condition that has been associated with the use of nitrogen-containing bisphosphonates. Reports describing this entity first appeared in the literature in 2003. While there have been significant numbers of case reports and a limited number of retrospective and prospective studies examining risk factors associated with ONJ, the pathophysiology of this condition remains elusive. In this review, we explore proposed mechanisms underlying ONJ development and identify potential areas for future investigation.

Serum calcium is not predictive of aggressive prostate cancer after radical prostatectomy

OBJECTIVES

To investigate the effect of preoperative total serum calcium on disease progression after radical prostatectomy (RP). Elevated total serum calcium has been linked to death from prostate cancer in the National Health and Nutrition Examination Surveys I and II. However, these findings have not been studied in a large cohort of patients with prostate cancer.

METHODS

We identified 10,532 consecutive patients who had undergone RP from 1990 to 2004 for prostate cancer. Total serum calcium levels were available for 7648 (72.6%) of these patients within 90 days before RP. Postoperative survival was estimated using the Kaplan-Meier method and compared using the log-rank test. Cox proportional hazard regression models were used to analyze the ability of serum calcium to predict biochemical recurrence, systemic progression, and cancer-specific survival.

RESULTS

The median patient age at surgery was 64 years. The median total serum calcium level was 9.4 mg/dL (range 6.8-11.2). On univariate analysis, the total serum calcium level was not significantly associated with any clinical or pathologic variables, including tumor stage, preoperative prostate-specific antigen, Gleason score, tumor volume, surgical margins, or lymph node status. Furthermore, the serum calcium level was not significantly associated with biochemical failure, systemic progression, or prostate cancer death on univariate or multivariate analysis.

CONCLUSIONS

The total serum calcium level was not predictive of cancer outcomes in patients who had undergone RP. Additional investigations of the preoperative disease predictors after RP for patients with nonmetastatic disease might be better directed toward other markers.

Fracture complicating the bone marrow edema syndrome

Bone marrow edema syndrome (BMES), also known as transient regional osteoporosis, is a rare and poorly understood disease process. We present a case of an elderly patient with the BMES who had a relapsing and remitting course complicated by a hip fracture which presented the unique and a previously unreported opportunity to examine the bony architecture pathologically. The patient responded well to calcitonin and bisphosphonate therapy after surgical repair of his fracture.This case highlights an underappreciated potential complication of BMES. Though not previously reported in the literature, BMES may be associated with active osteoporotic changes, with an infrequent risk of fracture that may be amenable to potential therapeutic interventions. Pathologically, BMES may represent a spectrum of disease consisting of an osteoclast-rich phase (transient regional osteoporosis phase) predisposing to fracture in addition to the more indolent osteoclast-poor phase with bone marrow edema more commonly associated with the disease. We hypothesize that it is the osteoclastic-rich phase which may benefit from early introduction of weight bearing activities, calcitonin, bisphosphonates, or parathyroid hormone. For example, bisphosphonates reduce bone resorption directly. Indirectly, bisphosphonates may also increase osteoblast differentiation and number and thus improve bone quality, an added benefit in the treatment of bone involved in the BMES, whether in the osteoclast-rich or osteoclast-poor phase.Further study should evaluate this osteoclastic-rich phase, which may be a transient pathologic phenomenon and which has not been described previously. Transient regional osteoporosis, therefore, may represent one point in the spectrum of the BMES. Hence, we would argue that BMES is a more accurate name for the full spectrum of this disease entity.

Incidence and risk factors for low trauma fractures in men with prostate cancer

BACKGROUND

Men with prostate cancer on androgen deprivation therapy (ADT) are at increased risk of bone loss. The present study sought to determine the incidence of low trauma fracture in men with prostate cancer (PC), and to characterize the association between potential risk factors and fracture risk in these men.

METHODS

In the prospective, population-based Dubbo Osteoporosis Epidemiology Study, 43 men aged 60+ years reported a history of prostate cancer; among whom, 22 men received ADT, and 21 men did not. Low-trauma fractures were ascertained between 1989 and 2004. Bone mineral density at the femoral neck (FNBMD), postural instability and lifestyle factors were obtained at baseline.

RESULTS

Men with prostate cancer had significantly higher lumbar spine BMD than those without cancer (p=0.013). During the follow-up period, 15 men with prostate cancer had sustained a fracture, yielding the age-adjusted incidence of fracture among this group was 31.6 per 1000 person-years, which was greater than those without cancer (22.1 per 1000 person-years). The age-adjusted incidence of fracture was more pronounced among those with prostate cancer on ADT (40.2 per 1000 person-years). After adjusting for age, the increase in fracture risk among prostate cancer patients was associated with lower femoral neck BMD (hazard ratio [HR] per SD=1.8, 95% CI: 1.0-3.4) and increased rate of bone loss (HR 2.3, 1.2-4.6).

CONCLUSIONS

Men with prostate cancer, particularly those treated with ADT, had an increased fracture risk. Although the average BMD in men with prostate cancer was higher than men without cancer, a low BMD prior to treatment or increased rate of bone loss after initiating ADT treatment was each a significant predictor of fracture in these.

Long-term outcome of phase I/II clinical trial of Ad-OC-TK/VAL gene therapy for hormone-refractory metastatic prostate cancer

We evaluated the long-term safety and efficacy of Ad-OC-TK (recombinant adenoviral vector carrying an osteocalcin promoter-driven herpes simplex virus thymidine kinase gene) plus VAL (valacyclovir) gene therapy for hormone-refractory prostate cancer. Ad-OC-TK/VAL therapy is the first in vivo adenovirus-mediated gene therapy to be used to treat metastatic prostate cancer, including bone metastasis. Six patients were enrolled in this trial, and two doses of Ad-OC-TK (2.5 x 10(9) or 2.5 x 10(10) plaque-forming units) were injected into locally recurrent tumor or bone metastasis on day 1 and day 8. Patients were also given VAL (3 g/day) for 21 days. Safety and efficacy were evaluated for at least 8 months in each patient. All patients tolerated this therapy with no serious adverse events. One prostate-specific antigen (PSA) response (from 318.3 to 4.9 ng/ml) was observed with a time to PSA progression (TTP) of 12 months. Docetaxel (30 mg/m2 per week) and estramustine (560 mg/day) combination chemotherapy (DE) was given to three docetaxel-naive patients on PSA failure after gene therapy. All three patients had a PSA response to DE therapy with 21, 7, and 4 months of TTP. These results suggest that additional trials are warranted.

Relevance of a new rat model of osteoblastic metastases from prostate carcinoma for preclinical studies using zoledronic acid

Animal models that mimic osteoblastic metastases associated with prostate carcinoma are required to improve the therapeutic options in humans. A new model was then developed and characterized in immunocompetent rats. The bisphosphonate zoledronic acid (ZOL) was tested to validate this model as a therapeutic application. Rat AT6-1 prostate tumor cells were characterized in vitro at the transcriptional (bone and epithelial markers) and functional (induction of mineralized nodules) levels. The bone lesions induced after their direct injection into the femur bone marrow were characterized by radiography, microscanner and histology analyses. ZOL effects were studied in vivo on bone lesion development and in vitro on AT6-1 cell proliferation, apoptosis and cell cycle analysis. Apart from epithelial markers, AT6-1 cells express an osteoblast phenotype as they express osteoblastic markers and are able to induce mineralized nodule formation in vitro. A disorganization of the trabecular bone at the growth zone level was observed in vivo after intraosseous AT6-1 cell injection as well as cortical erosion. The tumor itself is associated with bone formation as revealed by SEM analysis and polarized light microscopy. ZOL prevents the development of such osteoblastic lesions, related to a direct inhibitory effect on tumor cell proliferation independent of caspase 3 activation, but associated with cell cycle arrest. A new rat model of osteoblastic bone metastases was validated in immunocompetent rats and used to show the relevance of using ZOL in such lesions, as this compound shows bifunctional effects on both bone remodelling and tumor cell proliferation.

[Pathophysiology of bone metastases in urologic carcinomas]

The skeletal system is the most frequent metastatic site of hematogenous spread of urologic carcinomas. Osseus metastases are classified as osteoneutral, osteolytic, osteoblastic and combinations thereof. Osteolytic metastases lead to bone resorption by activating osteoclasts, while osteoblastic metastases stimulate osteoblasts by paracrine mechanisms. The local osteoblastic effect is associated with secondary systemic bone resorption. The use of bisphosphonates is now an established supportive therapy and newer treatment strategies including targeted intervention in the pathophysiology of bone metastases and radioimmunotherapy are being applied or will be coming soon.

Complications Arising in the Final Year of Life in Men Dying from Advanced Prostate Cancer

OBJECTIVES

There are sparse anecdotal data on complications occurring in the final year of life in men dying of prostate cancer. The study aim was to record such data together with the interventions necessary and subsequent outcomes.

METHODS

Using an established prostate cancer database detailing all men presenting to a single institute with the disease, case notes and the hospital electronic databases were examined from men diagnosed with hormone refractory prostate cancer that went on to die of their disease between January 1, 1995 and December 31, 2002 (n=226). The frequency of complications and subsequent therapeutic interventions within the final 12 months of life were recorded together with the effect of those interventions.

RESULTS

The most common incident complications arose in the lower urinary tract. Overall, 27% (61 men) had lower urinary tract complications (LUTS), 12% (n=27) had progressive renal failure, 10% (n=23) became anemic, and 9% (n=21) had persistent bone pain despite analgesia. Fourteen percent (n=37) had skeletal-related complications (including bone pain, fractures, and cord compression). One hundred four men (46%) had a cancer-related complication with 25% (n=56) requiring related intervention(s). An improvement was observed in over three quarters of men (76%) who received an intervention. These included "channel" transurethral resection of prostate (TURP) (14% of men; n=32), long-term urethral or suprapubic catheterization (7.5%; n=17), blood transfusion (7.5%; n=17), external beam radiation for pain (4.9%; n=11), nephrostomy tube or ureteric stent insertion (2.7%; n=6), and fracture fixation (2.2%; n=5).

CONCLUSIONS

The commonest adverse events in the final year of life in men dying of advanced prostate cancer are those of LUTS, renal failure, anemia, and bone pain with almost half of men developing at least one of these. The majority of men who had interventions demonstrated a subjective or objective improvement.

Palliative Treatment of Bone Metastases in Hormone-Refractory Prostate Cancer: Effects of Pamidronate on the Carboxyterminal Telopeptide of Type-I Collagen Level in Patients with Increasing Prostate-Specific Antigen Levels

PURPOSE

Bisphosphonates have been reported to be effective in reducing bone pain and skeletal-related events associated with bone metastases in hormone-refractory prostate cancer (HRPC). However, whether bone resorption is reduced primarily by these particular drugs is difficult to evaluate because patients with HRPC are usually treated with secondary or tertiary hormonal manipulations including second-line antiandrogens, high-dose diethylstilbestrol, or low-dose dexamethasone therapies, some of which may also be effective. Thus, we assessed changes in the level of the carboxyterminal telopeptide of type-I collagen (ICTP), a bone resorption marker, before and after pamidronate administration in HRPC patients with increasing prostate-specific antigen (PSA) levels.

PATIENTS AND METHODS

Twenty-one HRPC patients with bone metastases and increasing PSA levels were intravenously treated with pamidronate at a dose of 30 mg either every 2 or every 4 weeks. Pamidronate administration was started immediately after confirmation of three consecutive increases in the PSA level.

RESULTS

In 14 patients (67%), the ICTP levels decreased after the administration of pamidronate, despite increasing PSA levels. In 7 of these cases, the ICTP levels were lower than those recorded for 6 months or longer before the start of pamidronate administration. The characteristics of the responders were compared with those of the non-responders.

CONCLUSION

In 67% of the HRPC patients with increasing PSA levels, pamidronate reduced the accelerated turnover of bone metabolism caused by metastases of prostate cancer.

Effect of long-term oral bisphosphonates on implant wound healing: literature review and a case report

BACKGROUND

Bisphosphonates suppress osteoclast activity, and their intravenous use has been reported in hundreds of cases to be associated with osteonecrosis in the jaw. Little is known of the risks associated with long-term use of oral bisphosphonates despite their use for >10 years by an oral mode of delivery for the treatment of osteopenia, osteoporosis, and Paget's disease of bone. The purpose of this report is to review the literature associated with bisphosphonate use that could impact bone healing and to report a case of bone necrosis in a patient on long-term oral bisphosphonates.

METHODS

A Medline search was carried out to find relevant articles from both medical and dental literature between 1960 and 2006. A patient, who had been taking an oral bisphosphonate for >10 years, developed unexplained clinical signs of bone necrosis after routine dental implant placement. This case was followed, documented, and the treatment of the osteonecrosis described.

RESULTS

A summary of how bisphosphonates may play a role in wound healing is presented. The compromised healing noted in a patient, who was under long-term oral bisphosphonate use, was successfully treated with systemic antibiotics, local microbial mouthrinse, and aggressive defect management (detoxification and mixture of bone graft and tetracycline).

CONCLUSIONS

This case suggests that patients under long-term oral bisphosphonate use should be treated with caution. Well-controlled, prospective clinical trials on the effect of oral bisphosphonates on bone are warranted to determine which patients may be at risk for such complications.

Managing metastatic bone pain: the role of bisphosphonates

Approximately two-thirds of patients with bone metastases have severe and debilitating pain. Despite a range of treatments, about 25% of patients with painful bone metastases suffer from uncontrolled pain. Bisphosphonates are the standard care for the reduction of skeletal events associated with bone metastases. We review the efficacy of currently available bisphosphonates in cancer-related bone pain. Oral clodronate, intravenous (i.v.) pamidronate, and i.v. zoledronic acid have shown an analgesic effect in some studies. Both i.v. and oral ibandronate reduced bone pain in breast cancer patients with bone metastases and maintained bone pain scores below baseline levels for up to two years in clinical trials. Pilot studies of intensive i.v. ibandronate dosing show rapid and effective relief from moderate-to-severe bone pain in patients with breast cancer and other tumors. Phase III trials are warranted to compare the efficacy of bisphosphonates in treating bone pain and to confirm the effects of intensive dosing regimens.

Mechanisms of osteopontin and CD44 as metastatic principles in prostate cancer cells

BACKGROUND

The expression level of osteopontin correlates with the metastatic potential of several tumors. Osteopontin is a well-characterized ligand for the alphavbeta3 integrin. The present study was undertaken to elucidate the possible role of osteopontin/alphavbeta3 signaling in prostate cancer cell migration.

RESULTS

We generated stable prostate cancer cell (PC3) lines that over-express osteopontin (PC3/OPN), mutant OPN in the integrin binding-site (PC3/RGDDeltaRGA), and null for OPN (PC3/SiRNA). The following observations were made in PC3/OPN cells as compared with PC3 cells: 1) an increase in multinucleated giant cells and RANKL expression; 2) an increase in CD44 surface expression, interaction of CD44/MMP-9 on the cell surface, MMP-9 activity in the conditioned medium, and cell migration; 3) western blot analysis of concentrated conditioned medium exhibited equal levels of MMP-9 protein in all PC3 cells. However, zymography analysis demonstrated that the levels of MMP-9 activity in the conditioned media reflect the CD44 surface expression pattern of the PC3 cell lines; 4) although MMP-9 and MMP-2 are secreted by PC3 cells, only the secretion of MMP-9 is regulated by OPN expression. A strong down regulation of the above-mentioned processes was observed in PC3/OPN (RGA) and PC3/SiRNA cells. PC3/OPN cells treated with bisphosphonate (BP) reproduce the down-regulation observed in PC3/OPN (RGA) and PC3/SiRNA cells.

CONCLUSION

Rho signaling plays a crucial role in CD44 surface expression. BPs inhibits the mevalonate pathway, which in turn, prevents the prenylation of a number of small GTPases. Attenuation of Rho GTPase activation by BPs may have contributed to the down regulation of cell surface CD44/MMP-9 interaction, MMP-9 activation/secretion, and cell migration. Taken together, these observations suggest that CD44 surface expression is an important event in the activation of MMP-9 and migration of prostate cancer cells. The various steps involved in the above mentioned signaling pathway and/or the molecules regulating the activation of MMP-9 are potential therapeutic target.

Management of the Spectrum of Hormone Refractory Prostate Cancer

INTRODUCTION

In its advanced stages, hormone refractory prostate cancer (HRPC) is an incurable condition which consists of a spectrum of disease. This requires an integrated multidisciplinary approach by an uro-oncologic team supported by radiologists, skeletal surgeons and palliative care. Aim of this review was to critically evaluate the current and potential approaches to patients affected by HRPC.

MATERIALS AND METHODS

A comprehensive evaluation of available published data included analysis of published full-length papers that were identified with Medline and Cancerlit from January 1981 to January 2006. Official proceedings of internationally known scientific societies held in the same time period were also assessed.

RESULTS

Most men with hormone refractory prostate cancer will die of their disease in the absence of intercurrent illness, and the various conditions arising as a consequence of local and distal cancer progression commonly lead to a spectrum of morbidity requiring treatment. Recent data regarding docetaxel-based chemotherapy have shown small but significant improvements in survival and improvement in quality of life in men receiving treatment. However, this therapy may not be suitable for all patients. New agents used alone or in combination with docetaxel currently are under trial in an attempt to provide much needed improvements in outcome. Bone-targeted treatments, particularly late-generation bisphosphonates, have added to the range of options, reducing the incidence of skeletal complications in some men. Further work is needed to target their use more effectively, to explore their efficacy in combination with existing proven therapies and to develop new approaches to treat bone metastases. Complications arising as a consequence of upper and lower tract dysfunction, haematologic, neurologic and psychologic disorders are common. These complications often are amenable to effective treatment, but interventions may engender difficult clinical and ethical decisions.

CONCLUSIONS

Although HRPC is incurable, it is not untreatable, and that the clinical management embraces not just chemotherapy, but many interventional and supportive therapies. A holistic and supportive approach to patient care is vital for optimal management, and is best provided by a coordinated, multidisciplinary team including urologists and oncologists.

Bone-Directed Treatments for Prostate Cancer

Maintaining bone health in men who have advanced prostate cancer is an important goal of therapy. Low bone mass is prevalent in men who have prostate cancer, and long-term androgen deprivation therapy causes additional significant decreases in bone mineral density. The adverse effects of the disease and current treatment modalities on bone health are further compounded when patients develop bone metastases,which cause clinically significant skeletal morbidity. Treatment with bone-directed therapies, including intravenous bisphosphonates, radio-nuclides, and endothelin-1 antagonists, can provide palliative and therapeutic benefits for patients who have established bone metastases, and treatment with intravenous bisphosphonates may prevent the development of bone metastases.

Therapieoptionen beim hormonrefraktären Prostatakarzinom

For a long time, hormone-refractory prostate cancer was regarded as a chemoresistant tumor. The introduction of taxanes has prompted a change in this opinion. For the first time treatment with 75 mg/m(2) docetaxel every 3 weeks has evidenced a survival benefit in a phase III trial (median survival of 18.9 months versus 16.5 months with mitoxantrone). Further advantages were improved pain reduction and quality of life. Neutropenia was foremost among the side effects. Docetaxel is currently the standard treatment for hormone-refractory prostate cancer. The morbidity of metastatic hormone-refractory prostate cancer is influenced by bone metastases. Pain is a prominent feature. Skeletal complications are frequent. Therapy with 4 mg zoledronic acid reduced skeletal complications significantly in comparison to placebo. The most pronounced effect is the reduction of pathological fractures. Side effects include flu-like symptoms, muscle pain, and edemas. Zoledronic acid also belongs to the standard treatment of hormone-refractory prostate cancer with bone metastases.

Natural history and treatment of bone complications in prostate cancer

Bone metastases are highly prevalent in patients with prostate cancer, and they commonly present a therapeutic challenge. The natural history of prostatic bone metastases is characterized by skeletal morbidity, often producing distressing symptoms for individual patients and reducing patient autonomy and mobility. These bone metastases are usually radiologically osteoblastic, but there is also a strong osteolytic component as evidenced by marked increases in bone resorption markers. Malignant bone lesions can reduce the structural integrity of the skeleton, resulting in skeletal complications such as pathologic fracture, spinal cord compression, and severe bone pain, which adversely affect quality of life. Preclinical and clinical studies have provided insight into the pathophysiology of malignant bone disease from prostate cancer and suggest that bone-directed therapies, including radionuclides, endothelin-1 antagonists, and bisphosphonates, may provide both palliative and therapeutic benefits. Clinical investigations with these agents are underway in patients with prostate cancer to gain insight into the pathophysiology of bone metastases and to evaluate the role of bone-specific therapies in treating and preventing bone metastases.

Rationale for zoledronic acid therapy in men with hormone-sensitive prostate cancer with or without bone metastasis

Men with prostate cancer are at risk for bone loss and skeletal complications throughout the course of their disease. Bone loss is prevalent in many men with prostate cancer at initial diagnosis, and initiating androgen deprivation therapy results in accelerated bone resorption, leading to bone loss and an increased risk of fracture. These men are also at high risk for disease progression and bone metastases that can result in significant skeletal morbidity, including pathologic fracture, spinal cord compression, and debilitating bone pain requiring additional therapy. Excessive osteoclast activity plays a central role in the pathophysiology of bone disease at each stage of prostate cancer disease progression. Zoledronic acid, a highly potent inhibitor of osteoclast-mediated bone resorption, has increased bone mineral density in men receiving androgen deprivation therapy and is the only bisphosphonate that has shown statistically significant reductions in skeletal morbidity in patients with bone metastases from prostate cancer. Furthermore, preclinical evidence suggests that zoledronic acid has antitumor activity in prostate cancer models. Recently, a treatment algorithm was developed by the 3rd International Consultation on Prostate Cancer recommending the use of zoledronic acid for the prevention of skeletal complications in patients with bone metastases from prostate cancer, regardless of their hormone status, and for the prevention of treatment-induced bone loss in patients without evidence of bone metastases. According to this algorithm, zoledronic acid should be considered for the prevention of skeletal morbidity in patients with prostate cancer throughout their treatment continuum.

Lack of Prophylactic Effect of Incadronate on Skeletal Lesions Associated with Implants of Prostate Cancer

OBJECTIVES

To evaluate prophylactic effects of bisphosphonate (BP) on skeletal lesions induced by prostate cancer (CaP).

METHODS

Incadronate, a third-generation BP, was administered weekly for 4 weeks, with or without 4-week pre-administration, to rats whose calvaria had been inoculated with syngeneic CaP tissue.

RESULTS

The transplanted CaP grew up and caused bone resorption with osteoblastic changes regardless of incadronate treatment. Although decrease in bone resorption accompanied by reduced number of osteoclasts was shown by incadronate administration, pre-administration had no additional inhibitory effect on bone destruction and Ki-67 labeling indices of CaP cells were not altered.

CONCLUSIONS

These results indicate that application of BP alone is not sufficient to prevent skeletal lesions due to CaP in patients with high risk of bone metastases although it is useful in inhibition of cancer-induced bone resorption with osteoblastic changes.

The impact of osteoporosis in men treated for prostate cancer

Prostate cancer patients are at significant risk for SREs, with up to 50% of androgen-insensitive patients experiencing an SRE at 24 months. The risk increases with the duration and type of cancer treatment. SREs decrease HRQOL, increase the cost of care, and are associated negatively with overall survival. Screening men at greatest risk (slender white men and men with hormone refractory disease or metastatic disease) with BMD measurements, and initiating empiric therapy (vitamin D3, calcium, parenteral estrogens, bisphosphates) may be warranted.

Antimetastatic drugs in prostate cancer

Despite the benefits of local therapy with radical prostatectomy and radiation, many patients with prostate cancer require hormonal ablation. While chemotherapy has proven efficacy when the disease progresses to androgen-independent prostate cancer, patients ultimately succumb to the disease, thus the identification of other active therapies is needed. Future treatment modalities include molecular targeted therapies. Prostate cancer has been an ideal model to study the multiple steps required in the metastatic cascade. These steps have been utilized in the development of metastasis inhibitors. This review will present promising agents that have been tested preclinically or are undergoing clinical investigation for their abilities in preventing prostate cancer metastasis. Because prostate cancer metastasizes preferentially to the bone, special attention will be given to agents that interfere with this pattern of metastasis. Specifically, the efficacy of angiogenesis inhibitors, metalloproteinase inhibitors, inhibitors of prostate cancer cell- endothelial cell interactions, and bisphosphonates will be reported. In addition, the introduction of these novel agents has raised many questions as to the relevance and optimal utilization of current clinical trial designs. Issues regarding combination therapy with chemotherapy, optimal timing of treatment with metastatic inhibitors, and the need for surrogate endpoints for molecular targeted therapies will be discussed.

The Emerging Role of Bisphosphonates in Prostate Cancer

Bisphosphonates are a class of therapeutic agents originally designed to treat loss of bone density. It has been shown that the primary mechanism of action is inhibition of osteoclastic activity. Accumulating data show that these drugs are useful in diseases with propensities toward osseous metastases. In particular, they are effective in diseases in which there is clear upregulation of osteoclastic or osteolytic activity such as breast cancer and multiple myeloma. Despite the fact that osseous metastases in prostate cancer manifest as osteosclerosis rather than osteolysis, studies now show that bisphosphonates are useful in the management of this disease. In particular, they have demonstrated an impact on osteoporosis associated with hormonal therapy, bone pain from metastases, and skeleton-related events from prostatic adenocarcinoma. This review briefly summarizes the available clinical data on the utilization of bisphosphonates in the disease of prostate cancer.

Combined Analysis of Two Multicenter, Randomized, Placebo-Controlled Studies of Pamidronate Disodium for the Palliation of Bone Pain in Men With Metastatic Prostate Cancer

Purpose: Bone metastases occur in approximately 80% of patients with advanced prostate cancer. Pain is common in these patients. The purpose of this study was to evaluate the effect of an intravenous bisphosphonate, pamidronate disodium, on pain control in metastatic prostate cancer patients.

Patients and Methods: Two multicenter, double-blind, randomized, placebo-controlled trials were conducted in patients with bone pain due to metastatic prostate cancer, with disease progression after first-line hormonal therapy. Intravenous pamidronate disodium (90 mg) or placebo was administered every 3 weeks for 27 weeks. Efficacy was measured via self-reported pain score (Brief Pain Inventory), analgesic use, the proportion of patients with a skeletal-related event (SRE; defined as pathologic fracture, radiation or surgery to bone, spinal cord compression, or hypercalcemia), and a pilot quantitative measurement of mobility. Laboratory evaluations included serum prostate-specific antigen, interleukin-6, bone alkaline phosphatase, and urinary bone resorption markers.

Results: Results of the two trials were pooled. There were no sustained significant differences between the pamidronate and placebo groups in self-reported pain measurements, analgesic use, proportion of patients with an SRE, or mobility at week 9 or 27. Urinary bone resorption markers were suppressed in the pamidronate group compared with placebo.

Conclusion: Pamidronate disodium failed to demonstrate a significant overall treatment benefit compared with placebo in palliation of bone pain or reduction of SREs. Evaluation of more potent bisphosphonates in patients with prostate cancer is warranted.

The nonsteroidal effects of diethylstilbestrol: the rationale for androgen deprivation therapy without estrogen deprivation in the treatment of prostate cancer

PURPOSE

During the last 2 decades there has been an increase in the number of men with prostate cancer placed on luteinizing hormone releasing hormone (LH-RH) agonist therapy. In addition, the duration of individual therapy has extended from what was once only a few months to, in many cases, several years. As a result there has been an increase in the incidence of side effects, including osteoporosis, decreased cognitive abilities, vascular stiffness and fatigue. We explored the use of estrogen in the form of diethylstilbestrol (DES) as an alternative treatment for men with prostate cancer, and introduce the concept of androgen deprivation without estrogen deprivation. In doing so we hope to elucidate some of the nonhormonal nonsteroidal effects of DES. Furthermore, we hope to define the mechanisms by which DES can be useful when LH-RH agonist therapy or orchiectomy has failed.

MATERIALS AND METHODS

We comprehensively reviewed the literature from 1935 to the present regarding estrogen and antiandrogen therapy. Our search focused on issues pertaining to side effects, efficacy and nonsteroidal effects of antiandrogens and estrogens.

RESULTS

It is readily apparent from the literature that androgen deprivation with DES can achieve effective prostate cancer control with demonstrable benefits compared to conventional LH-RH agonist therapy. In particular, rates of bone resorption and osteoporosis are less with the use of estrogen therapies. Estrogen has a clear beneficial effect on cognitive function. The estrogen metabolite 2-methoxyestradiol has significant antiangiogenic and pro-apoptotic effects. These effects give estrogens an added anticancer effect not otherwise seen in conventional LH-RH agonist therapy.

CONCLUSIONS

The efficacy of 1 mg DES extends well beyond its androgen suppressive effects. Androgen deprivation without estrogen deprivation is a concept that deserves further attention in the urological community.

Immediate dual energy X-ray absorptiometry reveals a high incidence of osteoporosis in patients with advanced prostate cancer before hormonal manipulation

OBJECTIVE

To examine the incidence of osteoporosis in patients with advanced prostate cancer (using forearm densitometry) before commencing androgen deprivation therapy (ADT), as osteoporotic fractures are more frequent in patients with prostate cancer who have undergone either medical or surgical castration, because of rapid loss of bone mass.

PATIENTS AND METHODS

In all, 174 patients (mean age 74.6 years, range 46-90) with advanced prostate cancer presented over 2 years. Their forearm bone densitometry values were compared with those from 106 age-matched controls (mean age 74.3 years, range 66-90).

RESULTS

Of the 174 patients, 73 (42%) were osteoporotic (t score <or=- 2.5) and 65 (37%) were osteopenic (t score - 1 to - 2.4). This compares with a 27% incidence of osteoporosis in the control group (P = 0.022). There were also no significant correlations between prostate specific antigen levels, Gleason score, tumour stage, biochemical markers and the presence or absence of osteoporosis risk factors.

CONCLUSION

Patients with advanced prostate cancer requiring ADT have a high incidence of osteoporosis before treatment. In addition, osteoporosis in these men cannot be predicted from clinical or biochemical values. Therefore, bone densitometry should be used in all patients with advanced cancer requiring ADT, as the results have implications for the choice of cancer therapy and the prophylaxis for osteoporosis.

Prostate cancer and bone metastases: medical treatment

Prostate cancer is the most common malignancy in men in the United States. With the long natural history of the disease, management of skeletal morbidity related to advanced prostate cancer becomes a major public health issue. The standard of care in advanced prostate cancer is androgen deprivation therapy. This may accelerate the development of osteoporosis and further exacerbate the risks of having adverse skeletal-related events develop. Recently, the use of bisphosphonates in men who have not responded to androgen deprivation therapy has been shown to reduce the incidence of skeletal-related events with time. Questions remain as to whether bisphosphonates should be broadly applied to earlier stages of the disease or tailored to men at higher risk of having bone-related morbidity. Work is ongoing to improve other approaches to the medical treatment of bone metastases in patients with advanced prostate cancer including the use of radiopharmaceuticals and combined chemotherapy.

Rationale for the use of bisphosphonates in osteoblastic and osteolytic bone lesions

Various primary malignancies develop bone metastases, and the resultant skeletal complications cause significant morbidity/mortality in advanced cancer patients. Bone lesions associated with metastases are traditionally classified radiologically as either osteolytic or osteoblastic, and both types of lesions are associated with elevated levels of specific bone resorption markers. Some common aspects in the pathophysiology of bone lesions have prompted speculation that treatments for osteolytic metastases might also be effective for predominantly osteoblastic metastases, such as in prostate cancer. Potent osteoclast activity inhibitors, bisphosphonates have been successful in the treatment of osteolytic tumor bone disease. Zoledronic acid is the first bisphosphonate shown to have a direct clinical benefit in the treatment of osteoblastic bone metastases, reducing the number and rate of skeletal events in prostate cancer patients with metastatic bone disease. Moreover, the shorter, more convenient infusion time and similar safety profile of 4 mg zoledronic acid compared with 90 mg pamidronate presently make zoledronic acid the preferred therapy for treatment of bone metastases in patients with all types of advanced malignancy.

Background to and management of treatment-related bone loss in prostate cancer

Prostate cancer is a common disease among older men. Androgen suppression by either orchiectomy or administration of luteinising hormone-releasing hormone (LHRH) analogues is the mainstay of treatment. Since the use of prostate-specific antigen (PSA) serum testing has become widespread, however, the timing of endocrine therapy has expanded considerably to include patients with limited involvement of extraprostatic sites and patients presenting an isolated elevation of PSA after radical treatments. These patients are expected to be treated for a long time, since they have a rather low risk of disease progression and there is no recommended time limit for LHRH analogue therapy. The long-term adverse effects of androgen deprivation therapy, therefore, deserve more attention than they have received in the past. Osteoporosis represents a special concern for men with prostate cancer receiving androgen deprivation therapy. The rate of bone loss in these men seems to markedly exceed that associated with menopause in women, and fractures occur more frequently than in the healthy elderly male population. Serial bone mineral density (BMD) evaluation could allow the detection of patients with prostate cancer who are at greater risk of osteoporosis and adverse skeletal events after androgen deprivation therapy, such as patients already osteopenic or osteoporotic at baseline and men with rapid bone loss during treatment. BMD evaluated during treatment could also be a potential surrogate parameter of antiosteoporotic therapeutic efficacy. Treatment of bone loss induced by androgen deprivation comprises general prevention measures, antiosteoporotic drugs and the use of alternative endocrine therapies. Optimising lifestyle and diet is important, although it cannot completely prevent bone loss. Patients with nonsevere bone disease may benefit from calcium and vitamin D supplements. Men who are osteoporotic before androgen deprivation or men becoming osteoporotic during treatment and/or experiencing adverse skeletal events may also require bisphosphonates. The effectiveness of these drugs in preventing fractures has been shown in a single randomised study involving patients with osteoporosis, but it has not yet been established in a prostatic cancer population without bone metastases given androgen deprivation therapy. Different forms of endocrine therapy such as low-dose estrogens, antiandrogens and intermittent androgen ablation are under investigation. They could offer the advantage of avoiding (or limiting) treatment-related bone loss. In our opinion, however, the data available so far are not robust enough to recommend these alternative endocrine therapies instead of standard androgen deprivation in routine clinical practice.

Therapeutic benefit of bisphosphonates in the management of prostate cancer-related bone disease

A diversity of bone pathology is present in men with prostate cancer. Androgen deprivation therapy (ADT) can cause significant and progressive osteopoenia and osteoporosis. Bone is also the primary site for metastases leading to associated pain, skeletal fractures and hypercalcaemia. Bisphosphonate therapy decreases bone resorption, which may prevent or reverse loss of bone mineral density. Both pamidronate and zoledronic acid have proven efficacy in preventing ADT-induced bone loss. In a randomised, placebo-controlled trial, in men with hormone-refractory prostate cancer, there was a decreased incidence of skeletal- related adverse events in men receiving zoledronic acid. So far, randomised trials have failed to show improved pain control. Formalised guidelines are needed to help clinicians decide which patients should be treated with bisphosphonates, when to initiate therapy and for what duration.

Costs of prostate cancer, metastatic to the bone, in the Netherlands

OBJECTIVE

To quantify medical costs associated with bone metastases in patients with prostate cancer. Bone metastases in patients with prostate cancer are associated with considerable morbidity, negatively impact quality of life, and can add substantially to medical costs, given a median survival of 30-35 months from diagnosis of bone metastases.

METHODS

A retrospective cost analysis from both a community and university hospital in The Netherlands was conducted. Twenty-eight patient records (14 from each hospital) were investigated to assess the impact of skeletal-related events (SREs), including fractures, spinal cord compression, and radiotherapy, on total direct medical costs and cost of hospitalization. Costs are given in EUROS (Euros).

RESULTS

The average total cost of treatment was Euros 13,051 per patient over the 24-month follow-up period, which includes an average cost of Euros 6973 per patient to treat SREs. Treatment of SREs more than doubled total treatment costs. Patients in this analysis experienced, on average, one SRE per year, and the cost of SREs varied from Euros 1187 to Euros 40,948.

CONCLUSIONS

Occurrence of SREs contributes significantly to the cost of care for patients with advanced prostate cancer. These data suggest that bisphosphonates, which can reduce pain and SREs, may reduce healthcare costs.

The new bisphosphonate, Zometa (zoledronic acid), decreases skeletal complications in both osteolytic and osteoblastic lesions: a comparison to pamidronate

Bisphosphonates are the treatment of choice for lytic bone lesions associated with breast cancer. In contrast, bone lesions associated with prostate cancer are predominately osteoblastic. Zoledonic acid (Zol) is a new-generation bisphosphonate that is approximately 2-3 orders of magnitude more potent than pamidronate (Pam) in preclinical models and has demonstrated clinical efficacy in patients with both lytic and blastic lesions. Zoledonic acid (4 mg via 15 min infusion) every 3-4 weeks was directly compared to Pam (90 mg via 2 hr infusion) in 767 patients with breast cancer and bone metastases. The primary endpoint was the proportion of patients experiencing a skeletal-related event (SRE) over 13 months. Zoledonic acid was as effective as Pam, and the proportion of Zol-treated patients with an SRE (42% in the hormonal therapy strata and 44% in the chemotherapy strata) was comparable to the original studies comparing Pam to placebo. Among 371 breast cancer patients receiving hormonal therapy, the proportion of patients with an SRE was 47% for Pam vs. 57% for placebo (P = 0.057), and among 380 patients treated with chemotherapy, the proportions with an SRE were 43% for Pam vs. 56% for placebo (P = 0.008) at 12 months. Zoledronic acid (4 mg) has been compared to placebo in a randomized Phase III trial involving 422 men with hormone-refractory prostate cancer metastatic to bone. Zoledonic acid demonstrated a significant advantage over placebo for median time to first SRE (median not reached for Zol vs. 321 days for placebo; P = 0.011), the proportion of patients with an SRE over 15 months (33 vs. 44% for placebo; P = 0.021), and mean skeletal morbidity rate (number of SREs/time, 0.08 vs. 1.49 for placebo; P = 0.006). In addition, the effects of Zol were apparent early. At 3 months, only 12% of Zol-treated patients had an SRE vs. 23% for placebo (P = 0.003), and at 6 months, the proportions were 21 vs. 31% for placebo (P = 0.025). In contrast, a previous study of Pam in 236 prostate cancer patients found that Pam was no more effective than placebo in reducing bone pain or SREs over 6 months. In these studies, Zol was well tolerated with a safety profile similar to other IV bisphosphonates. In conclusion, Zol is the first bisphosphonate to demonstrate efficacy in both lytic and blastic disease. The unique properties of this novel agent should be further explored in future clinical trials.

State-of-the-art treatment of metastatic hormone-refractory prostate cancer

Initial therapy for advanced prostate cancer includes androgen ablation by surgical or medical castration. Still, nearly all men with metastases will progress to hormone-refractory prostate cancer (HRPC). Current U.S. Food and Drug Administration-approved agents for the treatment of HRPC include mitoxantrone and estramustine, although the vinca alkaloids and the taxanes have shown promising activity in single-agent phase II trials. Combinations of these agents induce a biochemical response in greater than 50% of patients, but the median duration of response is approximately 6 months. Overall survival of patients treated with these combinations is approximately 18-24 months. Studies are ongoing to develop novel therapies that target specific molecular pathways or mechanisms of chemotherapy resistance. Novel agents under development include growth factor receptor inhibitors, antisense oligonucleotides, bisphosphonates, and cell differentiating agents. Evaluation and incorporation of these agents into existing treatment regimens will guide us in the development of more active regimens in the treatment of HRPC.