Anti-tumour activity of bisphosphonates in human myeloma cells

Multiple myeloma is a haematological malignancy characterized by an expansion of malignant plasma cells within the bone marrow and is frequently associated with bone disease involving the development of osteolytic bone lesions, pathological fractures, osteoporosis and hypercalcaemia. A class of anti-resorptive drugs known as bisphosphonates have been in use to treat osteoclast-mediated bone diseases for the past 3 decades, and are currently proving effective in the treatment of the bone disease associated with multiple myeloma. Recent studies have suggested that bisphosphonate treatment may also result in an improvement in survival in some patients with multiple myeloma. These effects on survival may reflect an indirect effect of the bisphosphonates on tumour growth, via inhibition of osteoclast activity and hence a reduction in the release of tumour growth factors. However, it is also possible that bisphosphonates may have a direct effect on myeloma cells. In support of this we have demonstrated that bisphosphonates can decrease cell proliferation and induce apoptosis in human myeloma cells in vitro, and this review discusses the possibility that bisphosphonates may have not only an anti-resorptive action, but may also have a direct anti-tumour activity.     

Exploring the anti-tumour activity of bisphosphonates in early breast cancer

Bisphosphonates are potent inhibitors of osteoclast-mediated bone resorption and are firmly established in the management of breast cancer patients with metastatic skeletal disease. There are extensive data that bisphosphonates, particularly nitrogen-containing bisphosphonates such as zoledronic acid, exhibit anti-tumour activity potentially via both indirect and direct mechanisms in vitro. In vivo studies using animal models of breast cancer induced bone disease have shown that bisphosphonates exert anti-tumour effects via inhibiting osteolysis and reducing skeletal tumour burden. Furthermore, pre-clinical studies have demonstrated synergistic anti-tumour effects between chemotherapy agents commonly used in breast cancer treatment and nitrogen-containing bisphosphonates. This, coupled with emerging evidence from pre-clinical in vivo studies suggesting that bisphosphonates may have additional anti-tumour activity outside of the bone microenvironment, could be of significant importance in the clinical management of breast cancer. The evidence in favour of an anti-tumour effect of bisphosphonates in the clinical setting is inconclusive however, with conflicting evidence from several trials. This review focuses on the anti-tumour activity of bisphosphonates in breast cancer, with particular focus on zoledronic acid. The pre-clinical evidence for anti-tumour activity will be reviewed, followed by the synergistic effects with anti-cancer agents. Finally, the clinical relevance and strategies for the evaluation of anti-tumour activity in breast cancer will be discussed. We are currently exploring the potential synergistic anti-tumour effects of the sequential treatment of neoadjuvant chemotherapy followed by zoledronic acid in a randomised phase II study evaluating biological endpoints including apoptosis, proliferation and angiogenesis in patients with breast cancer.     

Management of Metastatic Bone Disease and Hypercalcemia of Malignancy

Thirty years of research have established bisphosphonates as the most effective agents for the inhibition of osteoclast-mediated bone resorption, and they play an important role in the management of malignant bone disease. Bisphosphonates have been systematically improved through chemical engineering, and the newest nitrogen-containing compounds, including zoledronic acid and ibandronate, are 1000-fold more potent than first-generation compounds. Consequently, they can be administered at low molar doses via short intravenous infusions without compromising renal safety. Bisphosphonates have a variety of metabolic effects on osteoclasts. Nitrogen-containing bisphosphonates inhibit protein prenylation via the mevalonate pathway, thereby inhibiting osteoclast activation and inducing apoptosis. Preclinical studies suggest that bisphosphonates also have direct and indirect antitumor activity. In animal models, bisphosphonates reduced skeletal tumor burden and bone metastases. Currently, intravenous bisphosphonates are the standard therapy for hypercalcemia of malignancy, and they have become an integral part of the treatment of bone metastases in conjunction with standard antineoplastic agents. Intravenous bisphosphonates quickly normalize serum calcium, reduce skeletal complications, and palliate bone pain in patients with bone metastases. Intravenous pamidronate (90mg via 2-hour infusion every 3–4 weeks) has, until recently, been the international standard for the treatment of osteolytic bone lesions from breast cancer or multiple myeloma. However, 4mg zoledronic acid (via 15-minute infusion) is quickly becoming the new standard based on evidence that it is as safe and effective as 90mg pamidronate in patients with breast cancer and multiple myeloma and significantly more effective for hypercalcemia of malignancy. Consequently, the American Society of Clinical Oncology guidelines for breast cancer and multiple myeloma recommend pamidronate or zoledronic acid for patients with radiographic evidence of osteolytic bone destruction. Moreover, 4mg zoledronic acid is the only bisphosphonate that has demonstrated significant clinical benefit in patients with other solid tumors, including lung cancer, and prostate cancer patients with primarily osteoblastic bone metastases. Bisphosphonates also may have activity in the adjuvant setting to prevent or delay the development of bone metastases. Studies with oral clodronate in early breast cancer have provided clinical evidence that bone metastases can be inhibited, and the studies are ongoing with more potent bisphosphonates. Bisphosphonates have also been shown to prevent cancer treatment-induced bone loss. These and other studies continue to redefine the role of bisphosphonates in the treatment of malignant bone disease and the management of bone health in cancer patients.     

Bisphosphonates in the Adjuvant Treatment of Breast Cancer

Bisphosphonates, as potent inhibitors of osteoclast-mediated bone resorption, significantly reduce the risk of skeletal complications in metastatic bone disease and also prevent cancer treatment-induced bone loss (CTIBL). However, more recently, there has been increasing data indicating that bisphosphonates exhibit anti-tumour activity, possibly via both indirect and direct effects, and can potentially modify the metastatic disease process providing more than just supportive care. The evidence from previous studies of an anti-tumour effect of bisphosphonates was inconclusive, with conflicting evidence from adjuvant oral clodronate trials. However, more recent trials using zoledronic acid have shown benefits in terms of disease-free and overall survival outcomes in certain subgroups, most evidently in older premenopausal women with hormone-sensitive disease treated with ovarian suppression, and in women in established menopause at trial entry. In the adjuvant setting, the use of bisphosphonates has also been focused on the prevention and treatment of CTIBL and recent guidelines have defined treatment strategies for CTIBL. The role of bisphosphonates in CTIBL in early breast cancer is well defined. There have been mixed results from large adjuvant metastasis-prevention studies of bisphosphonates, but there are strong signals from large subgroups analyses of randomised phase III trials suggesting significant anti-tumour beneficial effects in specific patient populations.     

Myeloma bone disease: pathophysiology and management.

Bone disease is a major feature of multiple myeloma. Myeloma-induced bone destruction is the result of an increased activity of osteoclasts, which is not accompanied by a comparable increase of osteoblast function. Recent studies have revealed that new molecules such as the receptor activator of nuclear factor-kappa B (RANK), its ligand (RANKL), osteoprotegerin (OPG), and macrophage inflammatory protein-1alpha are implicated in osteoclast activation and differentiation, while proteins such as dickkopf-1 inhibit osteoblastic bone formation. These new molecules seem to interfere not only with the biology of myeloma bone destruction but also with tumour growth and survival, creating novel targets for the development of new antimyeloma treatment. Currently, bisphosphonates play a major role in the management of myeloma bone disease. Clodronate, pamidronate and zoledronic acid are the most effective bisphosphonates in symptomatic myeloma patients. Biochemical markers of bone remodeling have been used in an attempt to identify patients more likely to benefit from early treatment with bisphosphonates. Furthermore, using microarray techniques, myeloma patients may be subdivided into molecular subgroups with certain clinical characteristics, such as propensity for lytic lesions that may need early prophylactic treatment. Recent phase I studies with recombinant OPG and monoclonal antibodies to RANKL appear promising.     

Optimising treatment of bone metastases by Aredia™ and Zometa™

Metastatic bone disease develops as a result of the many interactions between tumour cells and bone cells. This leads to disruption of normal bone metabolism, with the increased osteoclast activity seen in most, if not all, tumor types providing a rational target for treatment. The clinical course of metastatic bone disease in multiple myeloma, breast and prostate cancers is relatively long, with patients experiencing sequential skeletal complications over a period of several years. These include bone pain, fractures, hypercalcaemia, and spinal cord compression, all of which may profoundly impair a patient's quality of life. External beam radiotherapy and systemic endocrine and cytotoxic treatments are the mainstay of treatment in advanced cancers. However, it is now clear that the bisphosphonates provide an additional treatment strategy, which reduces both the symptoms and complications of bone involvement. Pamidronate (Aredia(TM)) is the most widely evaluated bisphosphonate and is recommended for most patients with multiple myeloma or breast cancer with bone metastases. Current research aims include the evaluation of new potent bisphosphonates such as zoledronic acid (Zometa(TM)). It is hoped that this compound is not only more convenient and easier to administer but also more effective in inhibiting skeletal morbidity. Zometa may also have some direct anticancer activity. Preclinical studies with Zometa have demonstrated its potential in malignant bone disease. Clinical studies in treatment of hypercalcemia of malignancy have been completed, as have Phase I and II trials in patients with cancer and pre-existing bone metastases. Three randomized, double-blind, controlled Phase III trials are now ongoing to establish the efficacy and safety of Zometa in treatment of bone metastases in patients with osteolytic and osteoblastic lesions. Additionally, new specific molecules such as osteoprotogerin have been developed that are based on our improved understanding of the cellular signalling mechanisms involved in cancer induced bone disease. These potent molecules are now entering clinical trials. Ongoing research is aimed at trying to define the optimum route, dose, schedule and type of bisphosphonate in metastatic bone disease and their use in the prevention and treatment of osteoporosis in cancer patients. In vitro suggestions of direct anti-cancer activity and some promising clinical data in early breast cancer have resulted in considerable interest in the possible adjuvant use of bisphosphonates to inhibit the development of bone metastases.     

Bisphosphonates and bone metastases]

Bisphosphonates, potent inhibitors of bone resorption have been emerging as the standard treatment of tumor-induced hypercalcemia during the 90's. All uncontrolled phase II studies up to 1992 had demonstrated efficacy in reducing morbidity in terms of bone pain, fracture and hypercalcemia. Other studies on intravenous bisphosphonates, with no other anti-tumor treatment, even demonstrated sclerosis of osteolytic breast cancer bone metastases. Randomised phase III studies only began after 1992. In multiple myeloma, one study with oral clodronate has reported a decrease in bone events and two other studies, one with intravenous pamidronate and the other with oral clodronate have both reported a decrease in skeletal events and bone pain. In breast cancer patients with bone metastases, five large studies have been reported: three with intravenous pamidronate, one with oral pamidronate and one with oral clodronate. All these studies have demonstrated the superiority of bisphosphonates over placebo on both bone pain and bone events, but have failed to show an increase in duration of survival. Bisphosphonates should therefore be considered as an important part of the palliative treatment in breast cancer patients with bone metastases. On the other hand, no definite conclusion can be drawn on the role of bisphosphonates in the treatment of prostatic carcinoma bone metastases yet. However, bisphosphonates should be considered as part of the standard therapy in managing painful lesions in patients with multiple myeloma, breast cancer and prostatic cancer. Nevertheless, further studies are needed with bisphosphonates in the adjuvant setting before bone metastases appear. Could new and more potent bisphosphonates such as zoledronate further reduce bone metastases morbidity?     

Aetiology of bone disease and the role of bisphosphonates in multiple myeloma

Osteolytic bone disease is a major cause of morbidity in patients with multiple myeloma. Our understanding of the pathophysiology of multiple myeloma has increased substantially during the past decade. However the underlying mechanisms of bone destruction and the treatments available have, until recently, received relatively little specific attention. In this review, we provide an overview of the RANK/RANKL/osteoprotegerin system; we describe its interaction with other cellular mechanisms, through which malignant plasma cells drive osteolysis, and explain how bisphosphonates can be used to block this action. We also review the supporting evidence for bisphosphonates as the treatment of choice for patients with bone complications related to multiple myeloma, and discuss possible developments for targeted therapy in the future.     

Bone disease in myeloma

Opinion statement The major clinical manifestation of multiple myeloma results from osteolytic bone destruction. The only currently Food and Drug Administration-approved drug for the treatment of the bony complications of multiple myeloma is monthly intravenous pamidronate at a dose of 90 mg infused over 4 hours. Recent studies have shown the safety of 2-hour infusions. A randomized trial comparing pamidronate to placebo continued to show benefits throughout the 21-month trial. Although the duration of therapy has not been firmly determined, it is likely that discontinuation of this drug will be met by enhanced bone loss and an increased risk of bony complications for these patients. Thus, it is recommended that the drug be continued indefinitely. Support for this recommendation also comes from the reduced bone density observed in women with postmenopausal osteoporosis following the withdrawal of bisphosphonate treatment. Recent attempts to give higher doses, more frequent infusions (every 2 weeks or less), or more rapid infusions (1 hour or less) of pamidronate have occasionally been associated with albuminuria and azotemia. These modifications should therefore be avoided. Importantly, the drug can be safely administered at 90 mg monthly to patients with poor renal function. The use of pamidronate for myeloma patients without lytic bone involvement or with Durie-Salmon stages I or II disease has not been evaluated. However, it is recognized that most patients with earlier stages of disease or without lytic bone involvement also develop bony complications. There is no reason to believe that these patients would not benefit from monthly intravenous infusions of pamidronate. The potential antimyeloma effect of this agent is another reason to administer this drug in these types of patients. Thus, it is our practice to administer monthly pamidronate to myeloma patients regardless of stage or bone involvement. However, trials evaluating oral bisphosphonates have produced inconsistent clinical results, probably as a result of the erratic and scanty poor absorption as well as poor oral tolerability of these drugs. Although these oral agents may be useful in some patients, it is impossible to identify which myeloma patients will benefit from orally administered bisphosphonates. The more potent nitrogen-containing bisphosphonate zoledronic acid more effectively reverses hypercalcemia of malignancy than pamidronate, and it appears promising in reducing bone loss in cancer patients. However, its efficacy in preventing skeletal complications is still being evaluated. Many other types of new agents are in early clinical trials, but their efficacy remains unproven at the present time.     

Bisphosphonates and radiation therapy for palliation of metastatic bone disease

Radiotherapy is an established treatment for metastatic bone pain. It may be delivered as a localised low dose treatment for localised bone pain or systemically for more widespread symptoms using hemibody external beam radiotherapy or intravenous bone-seeking radioisotopes. Bisphosphonates have been shown to reduce morbidity from bone metastases when given to patients with asymptomatic disease from myeloma and primary breast and prostate cancers. They also reduce metastatic bone pain in these sites. In the absence of randomised data comparing radiotherapy with bisphosphonates in the same clinical setting, comparison of the response rates from individual trials of the two modalities suggests that the overall pain response in all tumour types from radiotherapy is around 80% compared to a similar rate in myeloma with bisphosphonates but only 40% in solid tumours. Optimal use of the two modalities requires further investigation but since they have different dose limiting toxicities their incorporation in a combined modality approach to metastatic bone pain is rational using the concepts of additive effect and spatial co-operation in which bisphosphonates provide background control alongside acute pain relief using radiotherapy. They are also an important alternative for bone pain where radiation tolerance has been reached or radiotherapy is not readily available.     

Prevention and Treatment of Myeloma Bone Disease

Osteolytic bone disease is the most common complication of multiple myeloma, resulting in skeletal-related events (SREs) that cause significant morbidity. Bone destruction in myeloma is due to an increased activity of osteoclasts coupled with suppressed bone formation by osteoblasts. Currently, bisphosphonates are the mainstay of the treatment of myeloma bone disease. Zoledronic acid and pamidronate have shown similar efficacy in reducing SREs in a randomized study in the conventional chemotherapy era. However, in a recent study (the Myeloma-IX trial of the UK Medical Research Council, MRC), zoledronic acid was found to be superior to clodronate in reducing SREs, but also it produced a survival advantage of approximately 10?months in patients with bone disease at baseline. During recent years, novel agents targeting bone have been used in myeloma. This review focuses on the established therapy of myeloma bone disease and also on recent advances in treatment that take advantage of the better understanding of the pathophysiology of bone disease.     

Management of bone metastases

Metastatic bone disease develops as a result of the many interactions between tumor cells and bone cells. This leads to disruption of normal bone metabolism, with the increased osteoclast activity seen in most, if not all, tumor types providing a rational target for treatment. The clinical course of metastatic bone disease in multiple myeloma, breast and prostate cancers is relatively long, with patients experiencing sequential skeletal complications over a period of several years. These include bone pain, fractures, hypercalcemia, and spinal cord compression, all of which may profoundly impair a patient's quality of life. External beam radiotherapy and systemic endocrine and cytotoxic treatments are the mainstay of treatment in advanced cancers. However, it is now clear that the bisphosphonates provide an additional treatment strategy, which reduces both the symptoms and complications of bone involvement. Additionally, new specific molecules such as osteoprotogerin have been developed that are based on our improved understanding of the cellular signaling mechanisms involved in cancer-induced bone disease. These potent molecules are now entering clinical trials. Ongoing research is aimed at trying to define the optimum route, dose, schedule and type of bisphosphonate in metastatic bone disease and its use in the prevention and treatment of osteoporosis in cancer patients. In vitro suggestions of direct anticancer activity and some promising clinical data in early breast cancer have resulted in considerable interest in the possible adjuvant use of bisphosphonates to inhibit the development of bone metastases.     

New insights in myeloma-induced osteolysis

Multiple myeloma (MM) is a plasma cell malignancy localized in the bone marrow (BM) and characterized by a high capacity for bone destruction. Almost all patients with MM have early osteolytic lesions, which result mainly from increased bone resorption related to stimulation of osteoclast recruitment and activity in the immediate vicinity of myeloma cells. The recent discovery of Osteoprotegerin (OPG) and the subsequent identification of its ligand RANKL have provided new insights in the regulation of osteoclastogenesis. The ratio OPG/RANKL is critical for the regulation of bone remodeling maintaining the balance between osteoblastic and osteoclastic activity. This review summarizes the new concept that myeloma cells induce in bone environment an imbalance in the OPG/RANKL system responsible for osteolysis observed in patients. Indeed, myeloma cells increase in bone environment the expression of the potent osteoclastogenic factor RANKL and decrease the osteoprotective factor OPG production. Biological mechanisms involved in these processes are discussed. Furthermore, the chemokines MIP-1alpha and MIP-1beta belonging to the RANTES family are potent osteoclastogenic factors produced by myeloma cells and participate in myeloma-associated bone disease. These data open new avenues for the treatment of bone disease in MM and highlight the promising therapeutical interest of RANKL inhibitors (OPG and RANK-Fc) and MIP-1 inhibitors in the management of myeloma-associated osteolysis, besides bisphosphonates.     

Bone complications in multiple myeloma

Multiple myeloma is the malignant proliferation of plasma cells involving more than 10% of the bone marrow. The bone complications associated with multiple myeloma include bone pain, pathologic fractures, hypercalcemia of malignancy and cord compressions. The principal pathophysiology of bone disease in multiple myeloma is a shift in the balance of bone remodeling toward bone resorption. In recent years, bisphosphonates have become an important treatment for the bone complications of multiple myeloma. Potent inhibitors of osteoclast activity, bisphosphonates interfere with biochemical pathways and induce osteoclast apoptosis. Bisphosphonates also antagonize osteoclastogenesis and promote differentiation of osteoblasts, as well as inhibiting other aspects of osteoclast homeostasis and metabolism. Several studies have evaluated treatment with bisphosphonates in patients with multiple myeloma, and have demonstrated the efficacy of clodronate (Bonefos; Anthra Pharmaceuticals; Princeton, NJ; www.bonefos.com), pamidronate (Aredia; Novartis Pharmaceuticals Corp; East Hanover, NJ; www.pamidronate.com) and zoledronic acid (Zometa; Novartis Pharmaceuticals Corp; East Hanover, NJ; www.us.zometa.com) in reduction of pain, reduction of SREs and survival. Moreover, recent data suggest direct and indirect antimyeloma activity of pamidronate and zoledronic acid.     

Management of bone lesions in multiple myeloma

Bone destruction is a key feature of multiple myeloma, which causes significant impairment of patients' activity. Some of the mechanisms regulating bone destruction have recently been clarified, and the management of bone diseases in myeloma patients has made considerable progress. Moreover,imaging techniques for screening bone lesions have been developed, such as PET scan or (99m)Tc scan, other than regular X-ray analysis. We describe here strategies for the management of bone disease in myeloma, e.g., ( I ) effective chemotherapy against myeloma cells, (II) decrease of osteoclasts by bisphosphonates, (III) surgical treatment of damaged bone, (IV) irradiation to lytic bone lesion and (V) other forms of supportive care. All of these approaches should be effectively integrated to improve the quality of life of myeloma patients.     

多发性骨髓瘤骨病临床诊疗专家共识（2021）

多发性骨髓瘤骨病(MBD)是多发性骨髓瘤(MM)患者的常见并发症,严重影响其生活质量和生存期,因此强调规范化的诊断和治疗。此次中国临床肿瘤学会(CSCO)指南工作委员会组织专家组,在2014版MBD专家共识的基础上进行了更新补充,推荐对于初治的MM患者,无论是否存在骨病的影像学证据,均应使用双膦酸盐和/或地舒单抗积极预防MBD及骨相关事件。在双膦酸盐使用期间,应该密切监测肾功能及颌骨改变,对于肾功能不全的患者需要减量甚至禁用,同时这类患者宜优先选用地舒单抗。希望本共识作为学术性指导意见,能够提供恰当的临床诊疗参考,以便使患者获得最佳的治疗,具体实施时应该根据患者的个体情况而定。     

Treatment strategies for skeletal complications of cancer

Skeletal complications are a common result of many cancers, particularly of multiple myeloma and bone metastases of solid tumors originating in the breast, prostate or lung. A number of treatment options are available, including radiotherapy, radiopharmaceuticals, surgery and chemotherapy. Recently, bisphosphonates have emerged as a promising new treatment option for bone complications of cancer. These agents are potent inhibitors of osteoclast activity that bind to the bone matrix, are released during bone resorption, and are subsequently internalized by osteoclasts, where they interfere with biochemical pathways and induce osteoclast apoptosis. Bisphosphonates also antagonize osteoclastogenesis and promote the differentiation of osteoblasts. As a result, bisphosphonates inhibit tumor-induced osteolysis and reduce skeletal morbidity. Bisphosphonates are generally well tolerated, although they have recently been associated with osteonecrosis of the jaw, a painful and debilitating side effect that is only beginning to be understood. Despite this concern, bisphosphonates are an important tool in the management of skeletal complications of cancer, providing benefits for the treatment of hypercalcemia, osteolytic lesions and fractures, as well as offering amelioration of pain and improvement in quality of life.     

Advances in multiple myeloma and spine disease

Progressive bone destruction is the hallmark of multiple myeloma (MM) and is responsible for principal morbidity in the disease. The spine is the most afflicted skeletal organ, and vertebral fractures have significantly contributed to its poor prognosis. The principal underlying pathologic mechanism causing bone disease in MM is a shift in the balance of bone formation and bone resorption toward bone resorption, and eventually total dissociation between the 2 processes occurs in latter stages of the disease. During the past decade bisphosphonates have become an important adjunctive treatment in the management of MM, in which they have shown the ability to reduce bony complications associated with the disease. Advances in minimally invasive surgical techniques, such as percutaneous vertebroplasty and kyphoplasty, offer these patients less-invasive options for the treatment of vertebral collapse and restoration of their normal function. This report reviews recent advances in the understanding of bone disease in MM, the role of bisphosphonates in the prevention of skeletal events, and available data regarding percutaneous vertebroplasty and kyphoplasty.     

Bisphosphonates in the prevention and treatment of bone metastases

Bisphosphonates have an established role in treating tumor-induced hypercalcemia and decreasing the incidence of skeletal-related events. Recent data suggest that these agents may also prevent skeletal metastases. This review explains how cancer metastasizes to bone and how bisphosphonates may block this process, with a summary of clinical trials supporting the use of bisphosphonates to treat and prevent bone metastases. For skeletal metastases in patients with breast cancer, multiple myeloma, or other solid tumors, bisphosphonates are important adjuncts to systemic therapy. Despite promising results in metastatic prostate cancer, additional trials are needed before bisphosphonates become part of standard treatment in this setting. Ongoing trials are evaluating the preventive role of the third-generation bisphosphonates in breast cancer patients. Until the results of these trials are presented, bisphosphonates should only become a component of adjuvant treatment in the context of a clinical trial. Bone loss, a common consequence of cancer treatment, should be treated with the usual measures indicated for the management of osteoporosis, including bisphosphonates.     

Effects of bone-targeted agents on cancer progression and mortality

Bone-targeted treatments with bisphosphonates and denosumab, which reduce bone resorption, are known to reduce the risk of skeletal complications and prevent treatment-induced bone loss in patients with malignant bone disease. Additionally, these drugs may modify the course of bone destruction via inhibitory effects on the "vicious cycle" of growth factor and cytokine signaling between tumor and bone cells within the bone marrow microenvironment. Effects of the drugs on the stem cell niche, direct effects on the cancer cells, and immune modulation may also contribute. In early-stage (stages I, II, and III) breast cancer, treatment with the bisphosphonate zoledronic acid has shown improvements in disease-free and overall survival. Improved survival was particularly notable in women with established menopause at diagnosis and in premenopausal women with endocrine-responsive disease who received treatment with goserelin, which suppresses ovarian function by inhibiting the production of ovarian hormones. Additionally, in castrate-resistant prostate cancer, treatment with denosumab delays the development of bone metastases. These results strongly support the adjuvant use of bone-targeted treatments but suggest that reproductive hormones are an important treatment modifier to take into account. In advanced-stage (stage IV, ie, metastatic) cancers, survival benefits have been observed in patients with multiple myeloma and in patients with other solid tumors with rapid rates of bone destruction who received treatment with zoledronic acid. Here, we have critically reviewed the increasing evidence to support a disease-modifying effect of bone-targeted treatment and discussed the impact on clinical management.