Robert E. Coleman

Clinical Features of Metastatic Bone Disease and Risk of Skeletal Morbidity

The skeleton is the most common organ to be affected by metastatic cancer and the site of disease that produces the greatest morbidity. Skeletal morbidity includes pain that requires radiotherapy, hypercalcemia, pathologic fracture, and spinal cord or nerve root compression. From randomized trials in advanced cancer, it can be seen that one of these major skeletal events occurs on average every 3 to 6 months. Additionally, metastatic disease may remain confined to the skeleton with the decline in quality of life and eventual death almost entirely due to skeletal complications and their treatment. The prognosis of metastatic bone disease is dependent on the primary site, with breast and prostate cancers associated with a survival measured in years compared with lung cancer, where the average survival is only a matter of months. Additionally, the presence of extraosseous disease and the extent and tempo of the bone disease are powerful predictors of outcome. The latter is best estimated by measurement of bone-specific markers, and recent studies have shown a strong correlation between the rate of bone resorption and clinical outcome, both in terms of skeletal morbidity and progression of the underlying disease or death. Our improved understanding of prognostic and predictive factors may enable delivery of a more personalized treatment for the individual patient and a more cost-effective use of health care resources.

Zoledronic acid reduces skeletal-related events in patients with osteolytic metastases: A double-blind, randomized dose-response study

This study evaluated the dose–response relation for zoledronic acid, a new generation high potency bisphosphonate, given as a 5‐minute infusion in patients with malignant osteolytic disease.

Bone health in cancer patients: ESMO Clinical Practice Guidelines

There are three distinct areas of cancer management that make bone health in cancer patients of increasing clinical importance. First, bone metastases are common in many solid tumours, notably those arising from the breast, prostate and lung, as well as multiple myeloma, and may cause major morbidity including fractures, severe pain, nerve compression and hypercalcaemia. Through optimum multidisciplinary management of patients with bone metastases, including the use of bone-targeted treatments such as potent bisphosphonates or denosumab, it has been possible to transform the course of advanced cancer for many patients resulting in a major reduction in skeletal complications, reduced bone pain and improved quality of life. Secondly, many of the treatments we use to treat cancer patients have effects on reproductive hormones, which are critical for the maintenance of normal bone remodelling. This endocrine disturbance results in accelerated bone loss and an increased risk of osteoporosis and fractures that can have a significant negative impact on the lives of the rapidly expanding number of long-term cancer survivors. Finally, the bone marrow micro-environment is also intimately involved in the metastatic processes required for cancer dissemination, and there are emerging data showing that, at least in some clinical situations, the use of bone-targeted treatments can reduce metastasis to bone and has potential impact on patient survival.

Bisphosphonates in oncology

Bone metastases result in considerable morbidity, often affecting quality of life and independence over years, and may place complex demands on health care resources. The bisphosphonates have been shown to reduce skeletal morbidity in multiple myeloma and solid tumours affecting bone by 30-50%. Quite appropriately, these agents are increasingly used alongside anticancer treatments to prevent skeletal complications and relieve bone pain. The use of bisphosphonates in early cancer has become increasingly important to prevent adverse effects of cancer treatments on bone health. These include chemotherapy induced ovarian failure and the use of aromatase inhibitors in breast cancer and androgen deprivation therapy in prostate cancer. Bisphosphonate strategies, similar to those used to treat post-menopausal osteoporosis, are the intervention of choice for patients with low bone mineral density or rapid bone loss, along with adequate calcium and vitamin D intake and a healthy lifestyle. There is a strong preclinical rationale for bisphosphonates to prevent metastasis, primarily through inhibition of the vicious cycle of metastasis within the microenvironment. Recent data suggest that adjuvant bisphosphonates, at least in some patient subgroups, may modify the course of the disease and disrupt the metastatic process, reducing the risks of disease recurrence. In comparison to most other cancer treatments, adverse events related to bisphosphonate therapy are generally mild and infrequent; thus, the benefits of treatment within licensed indications will almost always outweigh the risks.

Metastatic bone disease

The cancer patient with skeletal metastases now has a much improved range of treatment options with major advances in bone-specific drug therapy as well as radiotherapy and radiopharmaceuticals, orthopaedic surgery, and systemic anticancer therapy with cytotoxic and endocrine agents.Recent advances in the understanding of bone remodeling mechanisms and the interdependence of cancer cells and bone have been closely associated with development of the bisphosphonate drugs and newer agents such as osteoprotegerin (OPG). The bisphosphonates are potent inhibitors of osteoclast mediated bone resorption and appear to function either by induction of apoptosis in mature osteoclasts or by inhibition of formation of osteoclasts from progenitor cells. Bisphosphonates are the treatment of choice in tumor-induced hypercalcemia. Bisphosphonates have a clear role in reducing bone pain and skeletal complications, such as pathological fracture and are being evaluated in the prevention of bone metastases.Until recently, intravenous (IV) pamidronate has been the drug most commonly prescribed for oncological indications and oral clodronate has also been widely used in some countries outside the US. However, newer and more potent drugs, such as zoledronate, are increasingly having a major impact on routine therapy. Three of the largest ever bisphosphonate trials, using zoledronate in metastatic bone disease have recently been completed. In a breast and multiple myeloma trial in 1648 patients, zoledronate (4mg IV) was shown to be equivalent to pamidronate (90mg IV) in reducing skeletal events and was more convenient to administer. In trials in prostate cancer and a wide range of other solid tumor types affecting bone, both the number of patients with skeletal-related events and the rate of bone complications were reduced. The indications for bisphosphonates are, therefore, no longer constrained by tumor type.The assessment of response to therapy is a vital part of management of metastatic bone disease. Plain radiographs and the isotope bone scan remain widely used but have many limitations. Newer imaging techniques such as computerized tomography, magnetic resonance imaging, and positron emission tomography may be useful in selected situations. Recent research suggests that measurement of tumor markers and bone-specific markers will play an increasingly important role in assessment of response. In particular, bone resorption markers measuring collagen breakdown have potential as rapid, convenient, and inexpensive measures of response, with suppression of bone resorption into the normal range being an important aim of bone-specific treatments.

The anti-tumour activity of bisphosphonates

Bisphosphonates are stable analogues of pyrophosphate (PPi), an endogenous regulator of bone mineralisation. A number of placebo-controlled trials have demonstrated their positive impact on skeletal-related events (SRE) that occur as a consequence of metastatic or myelomatous bone disease. Based upon their chemical structure bisphosphonates can be classified into nitrogen-containing bisphosphonates, (N-bisphosphonates) (for example zoledronate and pamidronate) and non-nitrogen containing (for example, clodronate and etidronate), which more closely resemble PPi. Clinical trials investigating bisphosphonates in the preventative setting have shown bisphosphonates to not only delay occurrence of bone metastases in certain cancers, but in one trial, occurrence of non-osseous lesions was delayed, and survival was prolonged. Other trials however have shown the opposite. Likewise, in animal models of cancer and metastases, conflicting results have been obtained. In vitro work has concentrated on bisphosphonates direct action upon tumour cells and has found a variety of anti-tumour effects such as apoptosis induction, inhibition of cell growth, inhibition of invasive behaviour and inhibition of angiogenic factors. Furthermore it would appear that bisphosphonates have the potential to enhance anti-tumour activity of known cytotoxic drugs. Ongoing research aims to assess this further, in addition to determining more precisely the role of adjuvant bisphosphonates in cancers such as breast and prostate cancer.

Comparison of the effects of intravenous pamidronate and oral clodronate on symptoms and bone resorption in patients with metastatic bone disease

BACKGROUND There is considerable debate as to the optimum schedule of bisphosphonate treatment in advanced malignancy. Short term studies using symptomatic response and biochemical markers of bone resorption may provide useful insight into differences between agents. PATIENTS AND METHODS Fifty-one patients with metastatic bone disease were randomly allocated to either oral clodronate 1,600 mg daily (group 1), intravenous clodronate followed by the same schedule of oral clodronate (group 2). or intravenous pamidronate 90 mg monthly (group 3). No radiotherapy was delivered or other systemic anticancer treatments were allowed except for long term endocrine therapy. Bone resorption was assessed by measurement of urinary collagen crosslinks. At each visit a pain score was recorded. RESULTS Symptomatic response was more frequent in the pamidronate group than in patients receiving clodronate. Nine of sixteen patients experienced a sustained improvement in pain score in the pamidronate-treated group, in contrast to only 4 of 16 and 2 of 11 patients in groups 1 and 2, respectively. There was a significant improvement in pain scores in the pamidronate arm compared with the clodronate treated patients after both three months of treatment (P <0.01) and at the last measurement (P <0.05). Biochemical changes correlated with changes in the pain score (P = 0.01). CONCLUSION Intravenous pamidronate appears to be more effective than oral clodronate in both controlling symptoms and suppressing bone resorption.

Double-blind, randomised, placebo-controlled, dose-finding study of oral ibandronate in patients with metastatic bone disease

BACKGROUND Bisphosphonates are an important component of the treatment of metastatic bone disease but more potent, oral formulations are required to improve the effectiveness and convenience of treatment. An oral formulation of the new bisphosphonate, ibandronate (BM 21.0955) has recently been developed. PATIENTS AND METHODS One hundred ten patients with bone metastases (77 breast, 16, prostate, 3 myeloma, 14 others) were recruited from a single institution to this double blind placebo-controlled evaluation of four oral dose levels (5, 10, 20 and 50 mg) of ibandronate. No changes in systemic anti-cancer treatment were allowed in the month before commencing treatment or during the study period. After an initial four-week tolerability phase, patients could continue on treatment for a further three months without unblinding; patients initially allocated to placebo received ibandronate 50 mg. The primary endpoint was urinary calcium excretion (UCCR). Bone resorption was also assessed by measurement of pyridinoline (Pyr), deoxypyridinoline (Dpd), and the N-terminal (NTX) and C-terminal (Crosslaps) portions of the collagen crosslinking molecules. RESULTS Two patients did not receive any trial medication thus, 108 patients were evaluable for safety. Ninety-two patients were evaluable for efficacy. A dose dependent reduction was observed in both UCCR and collagen crosslink excretion. At the 50 mg dose level, the percentage reductions from baseline in UCCR, Pyr, Dpd, Crosslaps and NTX were 71%, 28%, 39%, 80% and 74% respectively. One or more gastrointestinal (GI) adverse events occurring in the first month of treatment were reported by six (30%), seven (33%), nine (39%), nine (41%) and eleven (50%) patients at the placebo, 5, 10, 20 and 50 mg dose levels respectively. One patient (20 mg dose) developed radiographically confirmed oesophageal ulceration. GI tolerability may have been adversely affected by concomitant administration of non-steroidal anti-inflammatory agents. Nine (8%) patients stopped treatment within the first month due to GI intolerability but these patients were evenly distributed across the five treatment groups. There was no difference in non-GI adverse events between groups. CONCLUSIONS Oral ibandronate has potent effects on the rate of bone resorption at doses which are generally well tolerated. Further development is appropriate to evaluate the effects of long-term administration in the prevention of metastatic bone disease and the management of established skeletal metastases.

Use of bisphosphonates in cancer patients

All bisphosphonates are characterized by a P-C-P bond in their structure, which promotes their binding to the mineralized bone matrix and subsequent inhibitory effects on bone resorption. The rest of the bisphosphonate molecule varies according to the structural modification of the side chain, features which determine the relative potency, side-effects and probably also the precise mechanism of action. Clodronate acts directly on mature osteoclasts and can have cytotoxic effects at the concentration which is necessary to suppress bone resorption. Nitrogencontaining bisphosphonates, however, such as pamidronate, are not toxic to the osteoclasts at therapeutic concentrations (1). For pamidronate, the principal site of action is believed to reside in the terminal differentiation and final activation of osteoclasts (2). However, findings obtained with alendronate, a bisphosphonate whose structure is very close to that of pamidronate, cast doubt on this hypothesis. It has been shown that alendronate preferentially goes to sites of active bone resorption and increases the membrane permeability of osteoclasts to Ca++ and other ions such as H+ and NH4+, making them unable to resorb bone (3). Injection of (14C)-alendronate in rats also indicates that bisphosphonates are deposited preferentially at sites on the bone surface beneath the ruffled border of the osteoclasts (4). The preferential localization of bisphosphonates to sites of bone resorption appears to contradict the well-known clinical observations that a radionuclide bone scan with technetium-labelled methylene bisphosphonate (MDP) is typically positive at sites of increased osteoblast activity and new bone formation-for example, Paget’s disease of bone, bone metastases of prostate and breast cancerand not at sites of pathological bone resorption-for example, multiple myeloma. Recent findings suggest that osteoblasts, or at least those lining the bone surface, could be the essential target cells for bisphosphonates with secondary effects on the osteoclasts, probably by a

Bisphosphonates and RANK ligand inhibitors for the treatment and prevention of metastatic bone disease.

Bisphosphonates (BPs) are potent inhibitors of osteoclast-mediated bone resorption, which is increased when cancer cells invade bone. BPs are an established treatment for cancer that has spread to bone, and effectively reduce pain and other skeletal-related events. New directions in metastatic bone disease (MBD) include personalised BP therapy, such as using bone markers to guide frequency of BP administration and bone targeting agents such as denosumab (AMG 162). Clinical trials strongly suggest that denosumab might play a defined role in the future management of MBD. In terms of potential anti-cancer activity, early data tentatively suggest that zoledronic acid might have a role to play in the prevention of metastatic disease, though whether this is a direct effect on cancer cells, or indirect via the bone marrow micro-environment, or both, is as yet undiscovered. The definitive answer as to the role of adjuvant BP in early cancer is being addressed, with over 20,000 patients with breast, prostate or lung cancer currently participating in adjuvant BP randomised trials. The results of these trials should be available in the next few years, and this will establish whether BPs given early in the course of cancer will be able to prevent the formation of metastases, bone or otherwise.