Randomized, placebo-controlled trial of clodronate in patients with primary operable breast cancer

Safety of Long-Term Administration of Bisphosphonates in Elderly Cancer Patients

BACKGROUND

To evaluate the effectiveness and tolerability of the long-term treatment bone metastases with pamidronate in older patients.

MATERIALS AND METHODS

Twenty-two ambulatory patients aged 70 or older were included in the study. The median age was 73 (range 70-77). Ten patients (46%) were affected by breast carcinoma, 7 (32%) by prostate carcinoma and 5 (22%) by multiple myeloma. Nine (40%) patients presented co-morbidity. All of the patients presented at least one metastatic lytic bone lesion measuring 1 cm or more in diameter; the median lesion number was 2 (range 1-4). Hormonal therapy or chemotherapy regimen, were allowed as clinically required. Patients were treated with a fixed dose of sodium pamidronate, 90 mg in 3 h infusion every 4 weeks.

RESULTS

Partial response was shown in 6 (28%) patients, stable disease in 11 (50%), and progression (PD) in 5 (22%). 2 out of 5 patients with PD presented skeletal-related events (SREs) such as bone fracture. The median treatment duration was 19 months. The treatment was well tolerated; in 5 patients (23%) a GI fever was observed, in 3 patients (18%) G1 nausea, and in 3 patients (14) G1 diarrhea. Two cases (9%) of acute renal insufficiency (creatinine 1.7 and 1.6 mg/dl), and 3 cases (14%) of hypocalcemia (7.6, 7.5 and 7.8 mg/dl) were also registered. The renal dysfunction was reversible and without consequence.

CONCLUSION

Our experience suggests that the bisphosphonates long-term administration is useful and did not cause significant side effects in elderly subjects. Low-grade pyrexia, nausea/vomiting, acute/reversible renal dysfunction and hypo-calcemia were the most frequent side effects reported. However, they were of low grade and in most cases, did not require dose modifications and/or hospitalization.

Bisphosphonates in the treatment of skeletal metastases

Metastatic bone disease puts an enormous burden on patients and health care resources. Disruption of normal bone homeostasis by bone metastases leads to troublesome skeletal complications, such as bone pain, pathologic fractures, hypercalcemia of malignancy, and spinal cord compression. Bisphosphonates are an effective treatment for skeletal complications. These agents act primarily by initiating biochemical processes that ultimately result in apoptosis of osteoclasts, but they also have a number of other antitumor functions (eg, inhibition of angiogenesis). At present, the most widely used bisphosphonates are oral clodronate and intravenous pamidronate and zoledronic acid. Although these agents are effective in reducing skeletal complications, they are associated with varying safety and convenience issues. More recently, the availability of ibandronate as intravenous and oral formulations represents a new alternative for the treatment of metastatic bone disease. Further studies are necessary to establish the comparative benefits of bisphosphonates in metastatic bone disease.

Profiling the safety and tolerability of bisphosphonates

Because patients with metastatic bone disease suffer a significant burden from their illness and from anticancer treatments, it is therefore important to minimize the side effects of bisphosphonates. The intravenous bisphosphonates, zoledronic acid and pamidronate, have tolerability issues that include a flu-like syndrome, injection-site reactions, and occasional renal toxicity. Because of the potentially severe nature of the renal toxicity, renal monitoring is required before each dose, with drug withdrawal if the patients' renal function deteriorates. Oral clodronate often causes gastrointestinal disturbances, particularly diarrhea; compliance is often poor because of the large tablet size and multiple daily dosing. Long-term data have shown that the bisphosphonate ibandronate is well tolerated either intravenously or orally, with a renal safety profile similar to placebo and no evidence of cumulative renal damage. Studies investigating the effects of 15-minute infusions and intensive dosing indicate that intravenous ibandronate given rapidly or at high doses is also well tolerated with no renal safety concerns. Taken together, these results suggest that the favorable safety profile of ibandronate provides an important alternative to existing bisphosphonate options for metastatic bone disease. Using ibandronate could improve patient acceptability and simplify management, with reductions in the need for safety monitoring and management of adverse events.

Medical management of skeletal metastasis

This article discusses general principles of medical management of bone metastases, including diagnosis and follow-up; management of specific symptoms; options for systemic treatment, including bisphosphonates; specific details about each cancer type; and future directions in therapy.

Toward New Horizons: The Future of Bisphosphonate Therapy

Bisphosphonate therapy has become a standard of care for patients with malignant bone disease. In addition, preclinical and preliminary clinical data suggest that bisphosphonates may prevent cancer-treatment-induced bone loss (CTIBL) and the development of malignant bone disease in patients with early-stage cancer. Patients who receive adjuvant hormonal therapy for breast cancer or androgen-deprivation therapy for prostate cancer are at an especially high risk for CTIBL because of reduced estrogenic signaling. Oral clodronate (Bonefos; Anthra Pharmaceuticals; Princeton, NJ), oral risedronate (Actonel; Proctor and Gamble Pharmaceuticals, Inc.; Cincinnati, OH), and i.v. zoledronic acid (Zometa; Novartis Pharmaceuticals Corp.; East Hanover, NJ) have all demonstrated promise in preventing CTIBL in patients receiving hormonal therapy for breast cancer. Zoledronic acid has demonstrated efficacy with the longest between-treatment interval (3-6 months) and is currently being investigated in the Zometa/Femara Adjuvant Synergy Trials (Z-FAST and ZO-FAST in the United States and Europe, respectively). In patients receiving androgen-deprivation therapy for prostate cancer, i.v. pamidronate (Aredia; Novartis Pharmaceuticals Corp.) and i.v. zoledronic acid both have demonstrated significant benefits over placebo, but only zoledronic acid produced significant increases in bone mineral density compared with baseline values. Additionally, bisphosphonates have demonstrated antitumor activities in preclinical models, and clinical trials with oral clodronate suggest that bisphosphonates might prevent or delay bone metastasis in patients with early-stage breast cancer. Clinical trials are investigating the effect of zoledronic acid on disease progression in patients with breast cancer, prostate cancer, and non-small cell lung cancer. The results of these clinical trials should further define the clinical benefit of bisphosphonates in the oncology setting.

Safety of Intravenous and Oral Bisphosphonates and Compliance With Dosing Regimens

Patients with advanced cancers--particularly breast and prostate cancers--are at high risk for bone metastasis, leading to accelerated bone resorption and clinically significant skeletal morbidity. Bisphosphonates are effective inhibitors of bone resorption and reduce the risk of skeletal complications in patients with bone metastases. The standard routes of administration for bisphosphonates used in clinical practice are either oral or i.v. infusion. Oral administration of bisphosphonates is complicated by poor bioavailability (generally <5%) and poor gastrointestinal tolerability. First-generation bisphosphonates, such as clodronate (Bonefos; Anthra Pharmaceuticals; Princeton, NJ), must be administered at high oral doses (1,600-3,200 mg/day) to achieve therapeutic effects, which leads to poor tolerability and compliance with oral dosing regimens. Infusion of bisphosphonates is associated with dose- and infusion-rate-dependent effects on renal function. In particular, high bisphosphonate doses (e.g., 1,500 mg clodronate) can cause severe renal toxicity unless infused slowly over many hours. In contrast, the newer, more potent bisphosphonates effectively inhibit bone resorption at micromolar concentrations, and the small doses required can be administered via relatively short i.v. infusions without adversely affecting renal function. Zoledronic acid (Zometa; Novartis Pharmaceuticals Corp.; East Hanover, NJ) is a new generation bisphosphonate, and the recommended dose of 4 mg can be safely infused over 15 minutes. The 90-mg dose of pamidronate (Aredia; Novartis Pharmaceuticals Corp.) and the 6-mg dose of ibandronate (Bondronat; Hoffmann-La Roche Inc.; Nutley, NJ) require 1- to 4-hour infusions. Intravenous bisphosphonates require less frequent dosing (once a month) and are generally well tolerated with long-term use in patients with bone metastases. Zoledronic acid has demonstrated the broadest clinical activity in patients with bone metastases.

Short-Term Intermittent Intravenous Clodronate in the Prevention of Bone Loss Related to Chemotherapy-Induced Ovarian Failure

Chemotherapy-induced ovarian failure causes rapid bone loss in premenopausal women with early breast cancer. The aim of the present study was to investigate the effect of intravenous intermittent clodronate during adjuvant chemotherapy in prevention of this rapid bone loss. 45 premenopausal women with early stage breast cancer were treated with adjuvant chemotherapy. In addition, all women were randomly allocated to receive either seven cycles of intravenous clodronate infusions (1500 mg each) parallel to the chemotherapy or no further therapy. The mean bone loss in the lumbar spine at 6 months was -0.5% in the clodronate group and -1.4% in the control group (p = 0.22) and, at 12 months, -3.9% and -3.6%, respectively (p = 0.62). Type I collagen metabolite PINP levels at six months were significantly lower in the clodronate group than in the control group: 22.6 microg/l (range 15.7-55.8 microg/l) and 44.0 microg/l (range 12.5-91.9 microg/l), respectively (p = 0.0001). At 12 months, no difference between the PINP levels in clodronate and control groups were seen. In conclusion, in this small study a short-term intermittent intravenous clodronate treatment did not seem to prevent clinically significantly the bone loss related to chemotherapy-induced ovarian failure in premenopausal women with early stage breast cancer, even though a significant reduction of a biochemical marker of bone turnover (PINP) was seen during the therapy.

Tamoxifen treatment reverses the adverse effects of chemotherapy-induced ovarian failure on serum lipids

In all, 146 premenopausal women with early stage breast cancer were treated with adjuvant chemotherapy. In addition, 5-year tamoxifen treatment was started after chemotherapy to those 112 patients with hormone-receptor-positive tumours while those with hormone-receptor-negative tumours received no further therapy. The serum lipid levels were followed in both groups. The levels of serum total and low-density lipoprotein (LDL) cholesterol increased significantly after chemotherapy only in patients who developed ovarian dysfunction. Total cholesterol increased +9.5% and LDL cholesterol +16.6% in patients who developed amenorrhoea (P<0.00001 and 0.00001, respectively). The cholesterol levels did not change in patients who preserved regular menstruation after chemotherapy. After 6 months of tamoxifen therapy, the total cholesterol decreased −9.7% and the LDL cholesterol −16.7% from levels after the chemotherapy, while the cholesterol concentrations remained at increased levels in the control group (P=0.001 and P<0.0001, respectively). The high-density lipoprotein cholesterol levels did not change significantly in either tamoxifen or control group. The effects of tamoxifen treatment on serum lipids after chemotherapy have not been studied before. Our current study suggests that adjuvant tamoxifen therapy reverses the adverse effects of chemotherapy-induced ovarian failure on total and LDL cholesterol and even lowers their serum levels below the baseline.

Adjuvant Therapy in Elderly Patients with Breast Cancer

The elderly population has been neglected by the traditional approach to clinical breast cancer research. Elderly women have been underrepresented in breast cancer clinical trials, with the majority of studies being restricted to patients aged < 70 years. Elderly patients frequently have comorbidities and/or impaired organ function. These facts may often lead to death from causes other than cancer, thus nullifying any possible benefit of adjuvant treatment; furthermore, they render extrapolation of standard treatment recommendations to the elderly potentially hazardous, particularly with respect to chemotherapy. Therefore, specific clinical trials are needed to investigate adjuvant treatments tailored for the heterogeneous older population.

Understanding treatments for bone loss and bone metastases in patients with prostate cancer: a practical review and guide for the clinician

Prostate cancer patients are at risk for developing bone loss and bone metastases. Clinicians prescribing ADT should appreciate the potential effects of ADT on BMD as well as the morbidity and mortality that can result from osteoporotic fractures. Measures to address the evaluation of patients and when to treat patients with significant bone loss have been discussed. Bisphosphonates effectively prevent loss of BMD in prostate cancer patients. Treatment of prostate cancer patients with established bone metastases with zoledronic acid should be considered strongly based on the results of the Saad study and other studies of patients with bone metastases with other malignancies. Zoledronic acid is approved by the US FDA for use in men with metastatic hormone-refractory prostate cancer and in the European Union for any patient with bone metastases, including prostate cancer patients,because of the beneficial impact of zoledronic acid on skeletal-related events. There is no validated method to determine which patients might benefit most from bisphosphonate therapy in this setting. Many questions about the use of bisphosphonate therapy in men with prostate cancer must be addressed, both in terms of the use in bone loss and bone metastases. These questions include: What is the optimal timing of therapy? Which bisphosphonate is best? What is the best dose and dose schedule? Do bisphosphonates effectively decrease skeletal fracture rates in patients with osteoporosis? How long should patients receive therapy? Are bisphosphonate "holidays" warranted? What are the long-term skeletal and renal toxicities? Is there a role for sequencing bisphosphonate therapy either before or after chemotherapy? Is bisphosphonate therapy synergistic with certain chemotherapy or other bone-targeted therapies? Which patients are the most likely to benefit from bisphosphonate therapy? What are clinically significant endpoints of bisphosphonate trials in patients with metastatic disease? Does inhibiting bone turnover also inhibit formation of bone metastases? Preliminary work in these areas has been completed, but more questions than answers are available. Given the rising costs of health care, it is imperative that these questions be addressed to best use the health care dollar while offering high-risk patients the best available therapy. At present, no data suggest that bisphosphonates should be used routinely to prevent BMD loss in men with normal BMD or to prevent the development of bone metastases in men with biochemical relapse. Continuing trials may give us guidance in the future.

Osteoporosis and breast cancer

Osteoporosis affects one in three women after the menopause and the incidence of osteoporotic fractures increases steadily throughout life. Breast cancer is the most common cancer in women, both before and after the menopause. In younger women, recovery from breast cancer has been achieved using aggressive chemotherapy and radiotherapy that can adversely affect bone tissue or induce premature menopause. In postmenopausal women, breast cancer and osteoporosis are common, and although both are dependent on estrogens this leads to conflicting implications for the diagnosis and treatment: estrogens reduce the risk of fractures but increase the risk of breast cancer. Estrogen supplementation is, therefore, contraindicated in patients with a history of breast cancer. Selective estrogen response modifiers (SERMs) hold great promise, as they decrease both the fracture risk via an estrogen-agonist effect on bone and the breast cancer risk via an estrogen-antagonist effect on the breast tissue. SERMs can be used after successful treatment for breast cancer. Bisphosphonates, which are potent bone resorption inhibitors, are widely used both in cancer patients and in the prevention and treatment of spinal and peripheral osteoporotic fractures. Contraindications are exceedingly rare, and the satisfactory safety profile of these agents can be expected to improve further with newly developed modes of administration. Whether the bisphosphonates currently used to treat osteoporosis (alendronate and risendronate) have beneficial effects on skeletal events related to cancer progression remains to be determined, however. In sum, selection of the optimal treatment for osteoporosis in a patient with breast cancer involves assessment of the risk/benefit ratio of each treatment option, based on patient age, other risk factors for osteoporosis, and the stage of breast cancer progression.

Bisphosphonates: new therapeutic agents for the treatment of bone tumors

Bisphosphonates (BPs) have been used successfully for many years to reduce the skeletal complications associated with the benign and malignant bone diseases that are characterized by enhanced osteoclastic bone resorption. Until recently, it was thought that the clinical efficacy of BPs in the treatment of cancer patients with bone metastases was purely a result of the inhibition of osteoclast-mediated bone resorption. However, recent studies have demonstrated that BPs inhibit the growth, attachment and invasion of cancer cells in culture and promote their apoptosis. These results suggest that BPs are also anti-cancer agents, raising the possibility that BPs could inhibit cancer-cell colonization in visceral organs. However, results from clinical trials are conflicting, and whether BPs possess anti-cancer effects or not remains controversial.

Osteonecrosis of the jaws associated with the use of bisphosphonates: a review of 63 cases

PURPOSE

Bisphosphonates are widely used in the management of metastatic disease to the bone and in the treatment of osteoporosis. We were struck in the past 3 years with a cluster of patients with necrotic lesions in the jaw who shared 1 common clinical feature, that they had all received chronic bisphosphonate therapy. The necrosis that was detected was otherwise typical of osteoradionecrosis, an entity that we rarely encountered at our center, with less than 2 patients presenting with a similar manifestation per year.

PATIENTS AND METHODS

We performed a retrospective chart review of patients who presented to our Oral Surgery service between February 2001 and November 2003 with the diagnosis of refractory osteomyelitis and a history of chronic bisphosphonate therapy.

RESULTS

Sixty-three patients have been identified with such a diagnosis. Fifty-six patients had received intravenous bisphosphonates for at least 1 year and 7 patients were on chronic oral bisphosphonate therapy. The typical presenting lesions were either a nonhealing extraction socket or an exposed jawbone; both were refractory to conservative debridement and antibiotic therapy. Biopsy of these lesions showed no evidence of metastatic disease. The majority of these patients required surgical procedures to remove the involved bone.

CONCLUSIONS

In view of the current trend of increasing and widespread use of chronic bisphosphonate therapy, our observation of an associated risk of osteonecrosis of the jaw should alert practitioners to monitor for this previously unrecognized potential complication. An early diagnosis might prevent or reduce the morbidity resulting from advanced destructive lesions of the jaw bone.

Oral ibandronate for the treatment of metastatic bone disease in breast cancer: efficacy and safety results from a randomized, double-blind, placebo-controlled trial

BACKGROUND

We report the first results of a randomized trial assessing a new oral aminobisphosphonate, ibandronate, in patients with bone metastases from breast cancer.

PATIENTS AND METHODS

Patients (n = 435) received placebo, or oral ibandronate 20 mg or 50 mg once-daily for 96 weeks. The primary efficacy measure was the number of 12-week periods with new bone complications [skeletal morbidity period rate (SMPR)]. Multivariate Poisson regression analysis assessed the relative risk reduction of skeletal-related events. Secondary efficacy analyses included bone pain and analgesic use. Adverse events were monitored.

RESULTS

SMPR was significantly reduced with oral ibandronate [placebo 1.2, 20 mg group 0.97 (P = 0.024), 50 mg group 0.98 (P = 0.037)]. Ibandronate 50 mg significantly reduced the need for radiotherapy (P = 0.005 versus placebo). The relative risk of skeletal events was reduced by 38% (20 mg dose) and 39% (50 mg dose) versus placebo (P = 0.009 and P = 0.005). The tolerability profile of ibandronate was similar to placebo.

CONCLUSIONS

Oral ibandronate is an effective and well-tolerated treatment for metastatic bone disease. The 50 mg dose is being further evaluated in clinical trials, and this dose was recently approved in the European Union for the prevention of skeletal events in patients with breast cancer and bone metastases.

Clodronate reduces vertebral fracture risk in women with postmenopausal or secondary osteoporosis: results of a double-blind, placebo-controlled 3-year study

The efficacy of oral clodronate 800 mg daily to reduce vertebral fractures was studied in 593 women with postmenopausal or secondary osteoporosis. The incidence of vertebral fractures was significantly reduced by 46%. The effect was not modified by the underlying cause of osteoporosis or other baseline factors including bone mineral density, QUS, weight, and smoking.

INTRODUCTION

This study aimed to determine if the bisphosphonate, clodronate (Bonefos), reduced the incidence of vertebral fractures in osteoporotic women.

MATERIALS AND METHODS

Women fulfilling the WHO criteria for osteoporosis at the lumbar spine (T-score </= -2.5) and/or with at least one prevalent vertebral fracture were recruited to a 3-year double-blind, placebo-controlled study. A total of 593 patients were randomized to two strata comprised of women with postmenopausal osteoporosis (I, n = 483) and secondary osteoporosis (II, n = 110). They received either clodronate 800 mg daily orally (n = 292) or an identical placebo (n = 301). All patients received a calcium supplement of 500 mg daily. BMD was measured at 6, 12, 24, and 36 months, and lateral spine radiographs were obtained at baseline and annually thereafter for vertebral morphometry.

RESULTS

Treatment with clodronate was associated with a significant increase in mean spine BMD over 3 years (percent change from baseline, 4.35 +/- 6.34% versus 0.64 +/- 6.02% in the placebo group, p < 0.0001). At the hip, clodronate maintained total BMD, whereas a significant decrease was observed in the placebo group (percent change from baseline 0.70 +/- 5.67% versus -3.03 +/- 6.32% in the placebo group, p < 0.0001). The changes at the spine and hip were similar in both strata. Incident vertebral fractures at 3 years were observed in 63 women in the placebo group and 33 patients receiving clodronate (relative risk, 0.54; 95% CI, 0.37-0.80; p = 0.001). Clodronate significantly reduced vertebral fracture risk in both strata and in women with or without prior vertebral fracture at baseline. Nonvertebral osteoporosis-associated fractures occurred in 21 women in the placebo group and in 14 women treated with clodronate. Treatment was well tolerated, with no significant difference in adverse event rates, including esophagitis, during clodronate treatment.

CONCLUSION

We conclude that clodronate 800 mg daily is a safe and effective treatment to reduce fracture risk in women with osteoporosis, regardless of causation.

Oral ibandronate reduces the risk of skeletal complications in breast cancer patients with metastatic bone disease: results from two randomised, placebo-controlled phase III studies

Although intravenous (i.v.) bisphosphonates are the standard of care for metastatic bone disease, they are less than ideal for many patients due to infusion-related adverse events (AEs), an increased risk of renal toxicity and the inconvenience of regular hospital visits. The use of oral bisphosphonate therapy is limited by concerns over efficacy and gastrointestinal (GI) side effects. There remains a clinical need for an oral bisphosphonate that offers equivalent efficacy to i.v. bisphosphonates, good tolerability and dosing convenience. Oral ibandronate, a highly potent, third-generation aminobisphosphonate, has been evaluated in phase III clinical trials of patients with bone metastases from breast cancer. In two pooled phase III studies, patients with breast cancer and bone metastases were randomised to receive oral ibandronate 50 mg (n=287) or placebo (n=277) once daily for up to 96 weeks. The primary end point was the skeletal morbidity period rate (SMPR), defined as the number of 12-week periods with new skeletal complications. Multivariate Poisson's regression analysis was used to assess the relative risk of skeletal-related events in each treatment group during the study period. Oral ibandronate 50 mg significantly reduced the mean SMPR compared with placebo (0.95 vs 1.18, P=0.004). There was a significant reduction in the mean number of events requiring radiotherapy (0.73 vs 0.98, P<0.001) and events requiring surgery (0.47 vs 0.53, P=0.037). Poisson's regression analysis confirmed that oral ibandronate significantly reduced the risk of a skeletal event compared with placebo (hazard ratio 0.62, 95% CI=0.48, 0.79; P=0.0001). The incidence of mild treatment-related upper GI AEs was slightly higher in the oral ibandronate 50 mg group compared with placebo, but very few serious drug-related AEs were reported. Oral ibandronate 50 mg is an effective, well-tolerated and convenient treatment for the prevention of skeletal complications of metastatic bone disease.

Cytostatic and Apoptotic Effects of Bisphosphonates on Prostate Cancer Cells

BACKGROUND

Bisphosphonates are potent inhibitors of bone resorption frequently used for breast cancer and myeloma-induced bone disease. Zoledronic acid has been recently shown to also reduce skeletal morbidity from prostate cancer.

METHODS

We have investigated the biological effects of bisphosphonates on PC-3 cell survival (MTT assay and DNA content). We compared four bisphosphonates at doses ranging from 10(-6) to 10(-4) M: clodronate, pamidronate, ibandronate and zoledronic acid. We analyzed cell cycle phases and assessed apoptotic effects of bisphosphonates by three different methods.

RESULTS

Clodronate exhibited only a slight inhibitory effect on cell growth. In contrast, aminobisphosphonates markedly decreased cell growth in a time- and dose-dependent manner exerting cytostatic and apoptotic effects. The largest effects were observed after six days of exposure to 10(-4) M bisphosphonates. Cytostatic effects were observed with all three aminobisphosphonates whereas apoptotic effects were especially evident after zoledronic acid incubation.

CONCLUSIONS

Aminobisphosphonates, especially zoledronic acid, markedly inhibited PC-3 cancer cell growth, through a variable combination of cytostatic and apoptotic effects. This activity could potentially contribute to the beneficial effects of bisphosphonates in prostate cancer patients with bone metastases.

Bisphosphonate induced growth inhibition of breast cancer cells is augmented by p38 inhibition

Bisphosphonates (BPs) inhibit osteoclast-mediated bone resorption. They also protect from cancer-induced osteolysis and inhibit breast cancer growth in vitro. Some breast cancer cell lines, however, are relatively resistant to the growth inhibitory effects of BPs. We studied the mechanism of BP resistance in human MDA-MB-231 breast cancer cells. We show that both pyrophosphate-resembling (p-) and nitrogen-containing (n-) BPs induce activation of p38 mitogen activated protein (MAP) kinase pathway in MDA-MB-231 cells in vitro. MDA-MB-231 cells stably expressing a dominant negative form of the p38 MAP kinase (p38/AF) exhibited a dramatic increase in growth inhibition in response to BPs in vitro, compared to control cells. SB203580, a specific inhibitor of the p38 MAP kinase, also augmented BP-induced growth inhibition of parental MDA-MB-231 cells. Similar results were obtained also in murine macrophage-like J774 cells in vitro. Finally, no BP-induced phosphorylation of p38, or augmentation of BP-induced growth inhibition by SB203580 were detected in MCF-7 or HCC38 breast cancer cells, which are more sensitive than MDA-MB-231 cells especially to n-BP induced growth inhibition. In conclusion, these results suggest that BPs activate the p38 pathway in MDA-MB-231 and J774 cells. This activation may be associated with increased survival or proliferation because inhibition of p38 augments BP-induced growth inhibition. These findings may apply to the development of novel approaches for the treatment of breast cancer.

Cancer metastasis therapeutic targets and drug discovery: emerging small-molecule protein kinase inhibitors

Cancer metastasis is a significant problem and a tremendous challenge to drug discovery relative to identifying key therapeutic targets as well as developing breakthrough medicines. Recent progress in unravelling the complex molecular circuitry of cancer metastasis, including receptors, intracellular proteins and genes, is highlighted. Furthermore, recent advances in drug discovery to provide novel proof-of-concept ligands, in vivo effective lead compounds and promising clinical candidates, are summarised. Such drug discovery efforts illustrate the integration of functional genomics, cell biology, structural biology, drug design, molecular/cellular screening and chemical diversity (e.g., small molecules, peptides/peptidomimetics, natural products, antisense, vaccines and antibodies). Promising therapeutic targets for cancer metastasis have been identified, including Src, focal adhesion kinase, the integrin receptor, the vascular endothelial growth factor receptor, the epidermal growth factor receptor, Her-2/neu, c-Met, Ras/Rac GTPases, Raf kinase, farnesyl diphosphate synthase (i.e., amino-bisphosphonate therapeutic target) and matrix metalloproteases within the context of their implicated functional roles in cancer growth, invasion, angiogenesis and survival at secondary sites. Clinical and preclinical drug discovery is described and emerging small-molecule inhibitors of protein kinases are highlighted.

Synthesis, characterization, and in vitro antitumor activity of osteotropic diam(m)ineplatinum(II) complexes bearing a N,N-bis(phosphonomethyl)glycine ligand

A series of osteotropic (bone-seeking) [(bis(phosphonomethyl)amino-kappaN)acetato-kappaO(2-)]platinum(II) complexes attached to diammine, ethane-1,2-diamine, cis-R,S-cyclohexane-1,2-diamine, trans-S,S-cyclohexane-1,2-diamine, or trans-R,R-cyclohexane-1,2-diamine has been synthesized in accord with the concept of drug targeting and characterized by elemental analysis, (1)H, (13)C, and (31)P NMR spectroscopy. The in vitro antitumor activity in ovarian cancer cells (CH1) has been determined by means of the MTT assay. In this cisplatin-sensitive cell line the complexes containing cyclohexane-1,2-diamine (chxn) displayed a high activity in comparison to the diammine and ethane-1,2-diamine counterparts. In agreement with structure-activity relationships of other chxn-containing platinum(II) complexes both [(bis(phosphonomethyl)amino-kappaN)acetato-kappaO(2-)](trans-cyclohexane-1,2-diamine)platinum(II) complexes show superior potency than the corresponding cis-congener whereas the trans-R,R isomer displays the highest activity. Within the series of complexes under investigation, potency decreases depending on the coordinated amine ligand in the following order: trans-R,R-chxn > trans-S,S-chxn > NH(3) > or = cis-R,S-chxn > en.

American Society of Clinical Oncology 2003 update on the role of bisphosphonates and bone health issues in women with breast cancer

PURPOSE

To update the 2000 ASCO guidelines on the role of bisphosphonates in women with breast cancer and address the subject of bone health in these women.

RESULTS

For patients with plain radiographic evidence of bone destruction, intravenous pamidronate 90 mg delivered over 2 hours or zoledronic acid 4 mg over 15 minutes every 3 to 4 weeks is recommended. There is insufficient evidence supporting the efficacy of one bisphosphonate over the other. Starting bisphosphonates in women who demonstrate bone destruction through imaging but who have normal plain radiographs is considered reasonable treatment. Starting bisphosphonates in women with only an abnormal bone scan but without evidence of bone destruction is not recommended. The presence or absence of bone pain should not be a factor in initiating bisphosphonates. In patients with a serum creatinine less than 3.0 mg/dL (265 mumol/L), no change in dosage, infusion time, or interval is required. Infusion times less than 2 hours with pamidronate or less than 15 minutes with zoledronic acid should be avoided. Creatinine should be monitored before each dose of either agent in accordance with US Food and Drug Administration (FDA) labeling. Oncology professionals, especially medical oncologists, need to take an expanded role in the routine and regular assessment of the osteoporosis risk in women with breast cancer. The panel recommends an algorithm for patient management to maintain bone health.

CONCLUSION

Bisphosphonates provide a supportive, albeit expensive and non-life-prolonging, benefit to many patients with bone metastases. Current research is focusing on bisphosphonates as adjuvant therapy. Although new data addressing when to stop therapy, alternative doses or schedules for administration, and how to best coordinate bisphosphonates with other palliative therapies are needed, they are not currently being investigated.

Should all adjuvant breast cancer patients receive a bisphosphonate?

This commentary discusses the report by Trevor Powles and colleagues on their double-blind, placebo-controlled randomised trial of 2 years' adjuvant oral clodronate. Although the reported survival benefit in the clodronate-treated group confirms the results of one prior study as well as the generally held view that bisphosphonates could be advantageous, the reviewer does not feel that the data support the universal use of this additional adjuvant therapy.

Extended safety profile of oral clodronate after long-term use in primary breast cancer patients

INTRODUCTION

Long-term safety and tolerance is paramount when treating women who are otherwise healthy after the primary adjuvant therapy of breast cancer. Efficacy and limited safety results of a large-scale clinical trial, using adjuvant oral clodronate to prevent bone metastases in primary breast cancer patients, have been reported previously, demonstrating a reduction in the rate of bone metastases during treatment. Here we present expanded safety and tolerability results for clodronate treatment from this trial (cut-off date extended from June 1997 to June 2000).

STUDY DESIGN AND METHODS

For this randomised, double-blind, placebocontrolled, multicentre study, patients were enrolled and randomised to receive oral clodronate (Bonefos) 1600 mg/day or placebo for 2 years. The total median treatment period plus follow-up was 5.5 years. Adverse events (AEs) and laboratory parameters were followed up regularly for the total study period. The 95% CIs were estimated for the difference in the rate of AEs between the treatment groups.

PATIENTS

A total of 1079 women with primary operable breast cancer were enrolled to the study; 538 received clodronate and 541 received placebo.

RESULTS

Overall incidence of AEs (96.5% of the patients) was the same in both treatment groups, although gastrointestinal disorders were significantly more frequent in the clodronate group during the total study period (66% vs 56.2%; 95% CI 4.0-15.6; p < 0.05). This was mainly due to an increase in non-severe diarrhoea beginning 3-4 months after treatment start. Serious AEs (SAEs) were reported for 39.4% of the patients receiving clodronate and 44.5% of those receiving placebo; no drug-related (clodronate or placebo) SAEs were identified. Clodronate significantly lowered mortality (98 deaths vs 129 deaths; hazard ratio 0.77; 95% CI 0.59-1.00; p = 0.047) reducing the risk of death over the total study period by 23%. AEs caused 58 early discontinuations (five drug-related events) in the clodronate group and 43 discontinuations (three drug-related events) in the placebo group.

CONCLUSION

These results indicate that in women with early breast cancer receiving adjuvant systemic therapy, oral clodronate for 2 years is generally well tolerated with no serious long-term sequelae, providing a safe, long-term therapy in the adjuvant setting.

The antineoplastic role of bisphosphonates: from basic research to clinical evidence

Bisphosphonates are now well established as successful agents for the prevention and treatment of postmenopausal osteoporosis, corticosteroid-induced bone loss and Paget's disease. Bisphosphonates have also recently become important in the management of cancer-induced bone disease, and they now have a widely recognized role for patients with multiple myeloma and bone metastases secondary to breast cancer and prostate cancer. Recent studies suggest that, besides the strong antiosteoclastic activity, the efficacy of such compounds in the oncological setting could also be due also to direct antitumor effect, exerted at different levels. Here, after a brief analysis of the chemical structure, we will review the antineoplastic and biological properties of bisphosphonates. We will start from well estabilished mechanisms of action and go on to discuss the latest evidence and hypotheses. In particular, we will review the antiresorptive properties in malignant osteolysis and the recent evidence of a direct antitumor effect. Furthermore, this review will analyze the influence of bisphosphonates on cancer growth factor release, their effect on cancer cell adhesion, invasion and viability, the proapoptotic potential on cancer cells, the antiangiogenic effect, and, finally, the immunomodulating properties of bisphosphonates on the gammadelta T cell population.

NSABP breast cancer clinical trials: recent results and future directions

Over the past 40 years, the National Surgical Adjuvant Breast and Bowel Project (NSABP) has conducted several large, randomized clinical trials evaluating various aspects of surgical and adjuvant therapy in patients with operable breast cancer. Results from these trials have contributed significantly in reducing the extent of surgical procedures and in improving the outcome of patients with early-stage breast cancer. Furthermore, they have helped to establish standards of care for the surgical management of invasive and non-invasive disease and for the use of adjuvant hormonal therapy and adjuvant chemotherapy for patients with negative as well as for those with positive axillary nodes. More recent trials are evaluating several new classes of promising drugs such as the aromatase inhibitors in postmenopausal women with invasive or intraductal breast cancer, the taxanes for patients with positive nodes and in the neoadjuvant setting and other targeted molecular therapies such as trastuzumab and bisphosphonates. Results from these ongoing and recently completed trials could improve outcomes and quality of life for patients with early-stage breast cancer.

Regulation of MMP-9 (gelatinase B) in activated human monocyte/macrophages by two different types of bisphosphonates

Metalloproteinases (MMP), particularly MMP-9 produced by the intratumor monocyte/macrophages, play an important role in tumor invasion and metastases. Recent clinical trials in patients with primary breast cancer suggest that bisphosphonates (BP), above all clodronate, may reduce bone metastases. The aim of the present study was to evaluate whether the effects of BPs on cancer dissemination include inhibition of MMP-9 production in human monocyte/macrophages. The effects of clodronate and pamidronate on the MMP-9 expression in and secretion from stimulated human monocyte/macrophages were measured using quantitative reverse transcriptase - polymerase chain reaction (RT-PCR) and enzyme-linked immunoadsorbent assay (ELISA), respectively. The MMP-9 mRNA levels remained relatively stable in the presence of clodronate. In contrast, pamidronate at 30 microM-300 microM increased the mRNA levels 5- to 10-fold. MMP-9 secretion was dose-dependently down-regulated by clodronate whereas pamidronate at 30 microM induced a 50% increase on MMP-9 secretion (p < 0.05), followed by a down-regulation at higher concentrations. The results suggest that MMP-9 is differentially regulated at mRNA and enzyme protein level by BPs, which affect ATP-dependent intracellular enzymes (clodronate) or post-translational modification of GTPases (pamidronate). These findings may have implications for the therapeutic use of these compounds.

The use of zoledronic acid in the management of metastatic bone disease and hypercalcaemia

Zoledronic acid is a potent, third generation, nitrogen-containing bisphosphonate, licensed for the management of skeletal metastases and hypercalcaemia of malignancy, both of which cause considerable morbidity. In the preclinical setting, zoledronic acid has demonstrated superior potency regarding inhibition of osteolysis and reduction of hypercalcaemia as compared with other bisphosphonates. Clinical trials have indicated that zoledronic acid is superior to pamidronate in suppressing osteolysis and in reducing hypercalcaemia of malignancy. Its main mechanism of action is induction of osteoclast apoptosis through inhibition of the mevalonate pathway. Zoledronic acid has also demonstrated direct anti-tumour activity both in vitro and in animal models, suggesting it may be of benefit in preventing the formation of bone metastases. Clinical trials are in progress, assessing the benefit of zoledronic acid in the adjuvant setting in both breast and prostate cancer.

Systematic review of role of bisphosphonates on skeletal morbidity in metastatic cancer

OBJECTIVE

To review the evidence for the use of bisphosphonates to reduce skeletal morbidity in cancer patients with bone metastases.

DATA SOURCES

Electronic databases, scanning reference lists, and consultation with experts and pharmaceutical companies. Foreign language papers were included.

STUDY SELECTION

Included trials were randomised controlled trials of patients with malignant disease and bone metastases who were treated with oral or intravenous bisphosphonate compared with another bisphosphonate, placebo, or standard care. All trials measured at least one outcome of skeletal morbidity.

RESULTS

95 articles were identified; 30 studies fulfilled inclusion criteria. In studies that lasted > or = 6 months, compared with placebo bisphosphonates significantly reduced the odds ratio for fractures (vertebral 0.69, 95% confidence interval 0.57 to 0.84, P < 0.0001; non-vertebral 0.65, 0.54 to 0.79, P < 0.0001; combined 0.65, 0.55 to 0.78, P < 0.0001), radiotherapy (0.67, 0.57 to 0.79, P < 0.0001), and hypercalcaemia (0.54, 0.36 to 0.81, P = 0.003) but not for orthopaedic surgery (0.70, 0.46 to 1.05, P = 0.086) or spinal cord compression (0.71, 0.47 to 1.08, P = 0.113). The reduction in orthopaedic surgery was significant in studies that lasted over a year (0.59, 0.39 to 0.88, P = 0.009). Use of bisphosphonates significantly increased time to first skeletal related event but did not increase survival. Subanalyses showed that most evidence supports use of intravenous aminobisphosphonates.

CONCLUSIONS

In people with metastatic bone disease bisphosphonates significantly decrease skeletal morbidity, except for spinal cord compression and increased time to first skeletal related event. Treatment should start when bone metastases are diagnosed and continue until it is no longer clinically relevant.

Bisphosphonates antagonise bone growth factors' effects on human breast cancer cells survival

Bone tissue constitutes a fertile 'soil' for metastatic tumours, notably breast cancer. High concentrations of growth factors in bone matrix favour cancer cell proliferation and survival, and a vicious cycle settles between bone matrix, osteoclasts and cancer cells. Classically, bisphosphonates interrupt this vicious cycle by inhibiting osteoclast-mediated bone resorption. We and others recently reported that bisphosphonates can also induce human breast cancer cell death in vitro, which could contribute to their beneficial clinical effects. We hypothesised that bisphosphonates could inhibit the favourable effects of 'bone-derived' growth factors, and indeed found that bisphosphonates reduced or abolished the stimulatory effects of growth factors (IGFs, FGF-2) on MCF-7 and T47D cell proliferation and inhibited their protective effects on apoptotic cell death in vitro under serum-free conditions. This could happen through an interaction with growth factors' intracellular phosphorylation transduction pathways, such as ERK1/2-MAPK. In conclusion, we report that bisphosphonates antagonised the stimulatory effects of growth factors on human breast cancer cell survival and reduced their protective effects against apoptotic cell death. Bisphosphonates and growth factors thus appear to be concurrent compounds for tumour cell growth and survival in bone tissue. This could represent a new mechanism of action of bisphosphonates in their protective effects against breast cancer-induced osteolysis.

Bisphosphonates: new indications and methods of administration

In the course of 2002, several new studies were published confirming the efficacy of bisphosphonate drugs in fracture prevention in patients with osteoporosis. Further evidence was provided of their long duration of action, making intermittent administration possible. The potent bisphosphonate zoledronate can be given at intervals of as long as 1 year and produces changes in bone density and in markers of bone turnover comparable with those seen with conventional daily oral dosing with alendronate or risedronate. If such regimens are proven to prevent fractures, their convenience is likely to result in their widespread adoption and potentially an increase in compliance with these medications. Further evidence has been presented documenting the value of bisphosphonates in preventing the skeletal complications of malignancy, and possibly in reducing mortality in patients with breast cancer. The role of bisphosphonates in osteogenesis imperfecta was further confirmed, and novel roles in ankylosing spondylitis, myelofibrosis, and hypertrophic pulmonary osteoarthropathy were suggested.

Bisphosphonates: expanded roles in the treatment of patients with cancer

Bisphosphonates are important inhibitors of osteoclastic bone resorption seen in patients with bone metastases associated with malignancy. Bisphosphonates are used in the treatment of patients with bone metastases and have been shown to reduce skeletal-related events and symptoms, contributing to improved patient outcomes and quality of life. These agents first were approved in the treatment of patients with osteoporosis and have been used for the past two decades in this role. Because bisphosphonates inhibit osteoclast-mediated bone resorption, the bone remodeling cycle slows down and an increase in bone mineral density occurs. These agents are useful in treatment for both hypercalcemia and pain, although they have not definitively shown improvement in survival time. Considerable interest exists in the use of bisphosphonates for prevention of bone metastases and their potential antitumor activity. These drugs are well tolerated and have minimal side effects, but they are not inexpensive. This article discusses the role of bisphosphonates in patients with cancer and future directions for further research.

Clodronate for treatment of bone metastases in hormone refractory prostate cancer

INTRODUCTION

Approximately 85% of patients who die from prostate cancer have bone metastases. Even though the radiological aspect of such metastases is osteoblastic, we currently know that these lesions are mixed, with coexisting blastic and lytic lesions, always beginning with bone lysis by osteoclast proliferation. Treatment options are palliative and have poor response, and when there is an improvement it is usually short-lived. This work intends to study the effect of clodronate in the treatment of skeletal complications of prostate cancer.

MATERIALS AND METHODS

In an open prospective study 32 patients with hormone refractory prostate cancer with metastases to bones were assessed, in the period between November 2000 and September 2002. Mean age was 69 years (51 to 83 years). Patients were previously assessed by a pain scale and Karnofsky index. They underwent bone scintigraphy, X-ray, dosage of prostate specific antigen (PSA) and biochemical tests before and following treatment (administration of intravenous clodronate every 28 days). The Student's t-test was used for statistical analysis.

RESULTS

Twenty-nine patients (90.6%) showed improvement after the first and the 2nd cycles, which persisted for at least 4 months. Average on the pain scale improved from 7.7 to 2.1 and Karnofsky index raised from 42 to 71. Radiological aspect of the metastases improved in 15 patients (46.8%) and side effects were low (only 2 patients - 6.2%).

CONCLUSION

Bisphosphonate was effective in the treatment of skeletal complications of prostate cancer, presenting an objective response in 90.6% of treated patients, with a marked improvement in the pain scale, Karnofsky index and consequently in the quality of life of patients, and with low side effects.

New insights into the actions of bisphosphonate zoledronic acid in breast cancer cells by dual RhoA-dependent and -independent effects

Zoledronic acid (ZOL) is a nitrogen-containing bisphosphonate and its use in reducing osteoporosis and cancer-induced osteolysis is increasing. Recent findings indicated that ZOL has a direct effect on cancer cells. In this study, the effect of ZOL was examined on the aggressive MDA-MB-231 breast cancer cell line. ZOL induces an important inhibition of cell invasion at low concentrations (1 microM). This is not explained by modifications of proteases involved in cell invasiveness (matrix metalloproteinases and urokinase-type plasminogen activator), but by a disorganisation of actin cytoskeleton due to RhoA inhibition related to its defective prenylation as it was reversed by geranylgeraniol (GGOH) and mimicked by the Rho selective inhibitor C3 exoenzyme. In addition, ZOL inhibits the chemotactic effect induced by stromal cell-derived factor 1(SDF-1), a chemokine greatly involved in cancer metastasis to bone. This effect is related to both reduction of cell motility induced by RhoA inhibition and to a decreased expression of CXCR-4, the SDF-1 receptor. Finally, ZOL reduces Cox-2 expression and, consequently, the secretion of prostaglandins E2 (PGE2) in a RhoA-independent manner. This inhibition could contribute to bone protection in breast cancers because PGE2 stimulates osteoclast-mediated bone resorption. In summary, new insights in the mechanism of ZOL action on aggressive breast cancer cells are demonstrated and could explain its beneficial action in both the reduction of osteolysis and prevention of metastasis.

Bone metastases in breast cancer

Patients with advanced breast cancer who develop bone metastases suffer from long-term skeletal morbidity. Complications of bone metastases include pain, pathologic fractures, and spinal cord compression, which have a significant impact on the quality of life of patients. Treatment options for patients with bone metastases include surgery, radiation, and analgesics to reduce bone pain and to prevent or repair fractures. Intravenous bisphosphonates can delay the onset of bone metastasis and reduce the percentage of patients who experience skeletal complications of bone metastasis, thus reducing skeletal morbidity. For the past 6 years, pamidronate disodium (90 mg administered by 2-hour intravenous infusion) has been the treatment of choice for the prevention of skeletal complications of bone metastases in patients with breast cancer. However, a more potent bisphosphonate, zoledronic acid (4 mg administered by 15-minute intravenous infusion), was approved for use and has improved efficacy in patients with bone metastases. Because of the increased efficacy and more convenient infusion time, zoledronic acid may become the new standard of care for the treatment and prevention of skeletal complications secondary to bone metastases in patients with breast cancer. Phase III clinical trials have shown that patients with an existing skeletal complication are more likely to develop subsequent complications compared with patients who have not experienced a complication. Therefore, zoledronic acid therapy should be initiated when the patient is diagnosed with bone metastasis.

Current and future status of adjuvant therapy for breast cancer

Adjuvant systemic treatments have greatly improved the prognosis of women with early breast cancer. Combination chemotherapy and, for patients with oestrogen receptor-positive (ER+) tumours, endocrine treatment has been found to reduce the frequency of relapse and improve survival. New adjuvant strategies include the introduction of taxanes into adjuvant chemotherapy schedules, the use of aromatase inhibitors in place of, or in addition to, tamoxifen, and the use of adjuvant bisphosphonates. Combination chemotherapy has been found to reduce the annual odds of recurrence and death in pre- and postmenopausal women. The benefits, however, are on average less in older patients. Anthracycline-based regimens are more effective than traditional regimens of cyclophosphamide, methotrexate, and fluorouracil (CMF). The benefits of adjuvant cytotoxic and endocrine treatments are additive. There is considerable debate as to the role of taxanes in adjuvant therapy. Improved outcome has been observed in one large trial, especially in those patients with ER-negative tumours. High-dose chemotherapy has not fulfilled its early promise. Ovarian suppression and/or tamoxifen remain the treatments of choice. The annual odds of relapse and death have been reduced by approximately one-third and one-quarter, respectively. Several very large studies are in progress to assess the potential of aromatase inhibitors in the adjuvant setting. Direct comparisons with tamoxifen, as well as switching after several years from tamoxifen to an aromatase inhibitor, are strategies under evaluation. Early results from one of these trials evaluating anastrozole (the Arimidex, Tamoxifen, Alone or in Combination [ATAC] trial) has reported a reduced relapse rate after a median follow-up of 3 years in favour of anastrozole. However, this was at the expense of accelerated bone loss, and strategies to minimise this side effect of aromatase inhibitors are under investigation. Although many studies have indicated that bisphosphonates prevent the development of metastatic bone disease in animals, the clinical role of prophylactic bisphosphonates in early breast cancer is not clearly defined. Three studies with oral clodronate have been published, two of them indicating a protective effect on the development of bone metastases and improved survival, and one suggesting a disadvantage to the use of adjuvant clodronate. Further large adjuvant trials with clodronate and zoledronic acid are in progress. Adjuvant bisphosphonates also have been found to reduce bone loss associated with cancer treatments and preserve skeletal health. It may be possible to replace the current oral regimens for prevention of bone loss with a single annual infusion of the highly potent bisphosphonate zoledronic acid.

Bisphosphonate therapy for patients with breast carcinoma

Bisphosphonates have become well established in the treatment of patients with metastatic bone disease, although the optimal use of these agents has not been defined clearly. Randomized, controlled trials have demonstrated that treatment with intravenous pamidronate can significantly reduce the rate of skeletal-related events in patients with bone metastases from myeloma or advanced breast carcinoma. To date, there are few data from controlled, randomized studies to support the use of bisphosphonates in patients with bone metastases from malignancies other than breast carcinoma and myeloma. The optimal duration of treatment is unknown. Recent data have demonstrated that prolonged treatment is tolerated well, with no obvious toxicity. Generally, treatment is continued irrespective of the development of skeletal-related events and until there is a substantial decline in performance status. The widespread use of bisphosphonates will have major financial implications. Retrospective studies have suggested that the cost-effectiveness ratio is high for patients with advanced breast carcinoma. These ratios may be improved by targeting therapy to patients at high risk of developing complications from skeletal metastatic disease. Among patients with skeletal metastases from breast carcinoma, a recent retrospective analysis demonstrated that patients with disease confined to the skeleton were at greater risk of pathologic fractures compared with patients who had additional extraosseous disease. It is interesting to note that approximately two-thirds of patients with advanced breast carcinoma in the randomized trials of intravenous pamidronate had disease confined to the skeleton. The use of markers of bone turnover to identify patients who are most likely to benefit from bisphosphonate therapy or to identify patients who will respond to such therapy is the subject of further investigation. There are conflicting data on the use of bisphosphonates as an adjuvant therapy. Currently, such treatment should occur only as part of a clinical trial. Bisphosphonates can be used to prevent bone loss as a result of therapy for malignant disease, e.g., premature menopause in patients with early breast carcinoma.

Overview of the clinical efficacy of investigational anticancer drugs

The purpose of this overview was to make a broad inventory of investigational drugs for medicinal cancer treatment and, specifically, to indicate the evidence of clinical efficacy. Information was retrieved from electronic database searches in Medline and CANCERLIT and relevant published reviews. As the most recent findings are first reported as conference abstracts, an important basis for identification of new drugs and clinical results was a hand search of 13,392 abstracts from five major recent cancer conferences. A total of 209 investigational approaches or drugs were identified and classified into one of eight groups according to proposed mechanism of action. For 28 drugs/approaches survival data were available from randomized controlled trials. Statistically significant benefit was observed for only 12. In earlier phases no or modest anticancer activity was reported. It is speculated that the expanding knowledge in tumour biology might not easily translate into new substantially better anticancer drugs.

Future directions in the treatment and prevention of bone metastases

Preclinical studies are providing a growing body of evidence that bisphosphonates, particularly nitrogen-containing bisphosphonates, have antitumor activity. Bisphosphonates induce tumor cell apoptosis and reduce skeletal tumor burden in tumor xenograft models. Clinical studies with daily oral clodronate suggest that bisphosphonates can prevent bone metastases when used in the adjuvant setting, but the effect on overall survival is less certain. The more potent nitrogen-containing bisphosphonates, i.e., pamidronate and zoledronic acid, have demonstrated antitumor activity at approximately 10- to 100-fold lower concentrations than clodronate in vitro. A number of important unanswered questions must be addressed regarding the optimal use of bisphosphonates for prevention of bone metastases. For example, when should treatment begin, how long must treatment be continued, and what are the optimal dose and schedule to achieve clinically meaningful antitumor effects? Adjuvant studies of zoledronic acid in patients with breast and prostate cancer are under development, and the results are eagerly anticipated.