Bisphosphonate therapy in metastatic breast cancer

Clinical review 165: Markers of bone remodeling in metastatic bone disease

Many cancers have a strong propensity to spread to bone. The processes involved in cancer dissemination to bone are complex and variable, and the changes in bone metabolism, once bony metastases have occurred, are usually profound. This review surveys the usefulness of bone markers in the diagnosis and follow-up of patients with malignant bone disease. In patients with established bone metastases, most markers of bone remodeling are abnormal compared with healthy controls or cancer patients without bone lesions. Although bone markers may have a potential as diagnostic tools in cancer patients, the available data do not allow final conclusions regarding the accuracy and validity of any of the presently used markers in the diagnosis of bone metastases. As regards monitoring of anticancer therapy, most markers of bone remodeling respond to active treatments. These indices therefore may have the potential to be used in the monitoring of antitumor therapies. However, most if not all of the available evidence on the use of bone markers in monitoring anticancer therapy is observational, and it remains unclear whether they have any beneficial effects on overall outcome. The same is true for their prognostic value, although evidence suggests that suppressed levels of bone formation or high rates of bone resorption are independent predictors of poor survival.

Efficacy of bisphosphonates in the management of skeletal complications of bone metastases and selection of clinical endpoints

Bisphosphonates are the current standard of palliative care for patients with bone lesions from breast cancer and multiple myeloma. This article discusses the selection of endpoints and statistical methods used to assess clinical efficacy of bisphosphonate therapies in patients with bone metastases. Recent studies of pamidronate and zoledronic acid have set the standards for the design and conduct of multicenter, randomized, placebo-controlled trials to assess the clinical benefit of bisphosphonates in patients with bone metastases. Studies of zoledronic acid have demonstrated objective, significant, and enduring benefits in patients with a broad range of primary cancers, including prostate cancer, using robust clinical endpoints. Other bisphosphonates, including clodronate, have been investigated for the treatment of bone metastases, but these studies have been relatively small. This review first considers issues of trial design and analysis, with particular emphasis on the statistical requirements for the rigorous analysis of multiple events occurring in the same patient, and then reviews the results of bisphosphonate trials in patients with breast or prostate cancers metastatic to bone in the light of these statistical considerations.

Bisphosphonates for the relief of pain secondary to bone metastases

BACKGROUND

Bisphosphonates form part of standard therapy for hypercalcemia and the prevention of skeletal events in some cancers. However, the role of bisphosphonates in pain relief for bony metastases remains uncertain.

OBJECTIVES

To determine the effectiveness of bisphosphonates for the relief of pain from bone metastases.

SEARCH STRATEGY

MEDLINE (1966-1999), EMBASE (1980-1999), CancerLit (1966-1999), the Cochrane library (Issue 1, 2000) and the Oxford Pain Database were searched using the strategy devised by the Cochrane Pain, Palliative and Supportive Care Group with additional terms 'diphosphonate', 'bisphosphonate', 'multiple myeloma' and 'bone neoplasms'. (Last search: January 2000).

SELECTION CRITERIA

Randomized trials of bisphosphonates compared with open, blinded, or different doses/types of bisphosphonates in cancer patients were included where pain and/or analgesic consumption were outcome measures. Studies where pain was reported only by observers were excluded.

DATA COLLECTION AND ANALYSIS

Article eligibility, quality assessment and data extraction were undertaken by both reviewers. The proportions of patients with pain relief at 4, 8 and 12 weeks were assessed. The proportion of patients with analgesic reduction, the mean pain score, mean analgesic consumption, adverse drug reactions, and quality of life data were compared as secondary outcomes.

MAIN RESULTS

Thirty randomized controlled studies (21 blinded, four open and five active control) with a total of 3682 subjects were included. For each outcome, there were few studies with available data. For the proportion of patients with pain relief (eight studies) pooled data showed benefits for the treatment group, with an NNT at 4 weeks of 11[95% CI 6-36] and at 12 weeks of 7 [95% CI 5-12]. In terms of adverse drug reactions, the NNH was 16 [95% CI 12-27] for discontinuation of therapy. Nausea and vomiting were reported in 24 studies with a non-significant trend for greater risk in the treatment group. One study showed a small improvement in quality of life for the treatment group at 4 weeks. The small number of studies in each subgroup with relevant data limited our ability to explore the most effective bisphosphonates and their relative effectiveness for different primary neoplasms.

REVIEWER'S CONCLUSIONS

There is evidence to support the effectiveness of bisphosphonates in providing some pain relief for bone metastases. There is insufficient evidence to recommend bisphosphonates for immediate effect; as first line therapy; to define the most effective bisphosphonates or their relative effectiveness for different primary neoplasms. Bisphosphonates should be considered where analgesics and/or radiotherapy are inadequate for the management of painful bone metastases.

Administration routes and delivery systems of bisphosphonates for the treatment of bone resorption

Geminal bisphosphonates (BPs) are a class of drugs considered to be stable analogs of pyrophosphate (P-O-P), a physiological regulator of calcification and bone resorption. A number of BPs have been approved for clinical use in Paget's disease, hypercalcemia of malignancy, and osteoporosis. The major disadvantage of the clinically utilized BPs is their poor oral absorption from the GI tract, typically less than 1% is absorbed. In addition, the BPs have been associated with adverse gastrointestinal effects in humans. The challenge for novel drug delivery systems is to achieve improved bioavailability and safety. In the first part of this review, we discuss the bioavailability of BPs, the effect of food on the absorption of BPs, the mechanism of BPs' absorption and the adverse gastrointestinal effects. In the second part of the review, various methods that have been used for improving the bioavailability of BPs are described. Dosage form strategies reviewed include the use of particular formulations for increasing oral absorption as well as decreasing adverse gastrointestinal effects, absorption enhancers, BP compounds and the solubility of their calcium complex/salts, and the prodrug approach. Because of the poor GI absorption, attempts have been made to enhance the bioavailability of BPs by several parenteral routes other than i.v. injections. Description of nasal administration, s.c. and i.m. injections, BP implants and targeted osteotropic delivery systems are reviewed.

Matrix metalloproteinases and their inhibitors in tumour growth and invasion

Controlled degradation of the extracellular matrix (ECM) is crucial for the growth, invasive capacity, metastasis and angiogenesis of tumours. Matrix metalloproteinases (MMPs), a family of zinc-dependent neutral endopeptidases that are collectively capable of degrading essentially all ECM components, apparently play an important role in all of these aspects of tumour development. In addition, there is recent evidence that MMPs are also important for tumour cell survival. At present, therapeutic intervention on tumour growth and invasion based on the inhibition of MMP activity is under intensive investigation, and several MMP inhibitors are already being used on malignant tumours of various organs in clinical trials. In this review we discuss the role of MMPs and their inhibitors in tumour invasion as a basis for prognostic purposes and for targeted therapeutic intervention in cancer.