An update on the currently available and future chemotherapy for treating bone metastases in breast cancer patients

ABSTRACT

Introduction: Bone metastases in breast cancer patients are a common clinical problem. Many factors influence the treatment decision, including tumor characteristics, previous treatment and tumor burden in the treatment of metastatic breast cancer.

Areas covered: This present review summarizes the new treatment strategies and the chemotherapeutic agents currently available in the management of metastatic breast cancer with bone metastases.

Expert opinion: Patients with bone metastases more often have hormone receptor-positive tumours. Although new treatment agents for metastatic breast cancer have been investigated, endocrine therapy is still considered as the treatment of choice for patients with bone metastases although chemotherapy still has an important place. In recent years, new chemotherapeutic agents such as etirinotecan and nab-paclitaxel have been established though there are few studies that have looked at particular types of metastases. In the last decade, therapies for bone metastasis resistant to endocrine therapy have predominantly focused on radiotherapy, surgical resection, chemotherapy, bone-targeting radiopharmaceuticals and targeted therapeutics. New targeted agents include: Src inhibitors, cathepsin K inhibitors, CXCR4 inhibitors, TGF-B blockade and integrin antagonists while drug delivery systems for chemotherapy have also been developed. These new treatment options could be future treatment options for bone metastatic disease if early promising results are confirmed by clinical trials.

KEYWORDS:

• Bone metastasis
• breast cancer
• chemotherapy
• targeted therapy
• drug delivery systems

Article highlights

• Bone metastases develops in 65-75% of patients with late-stage breast cancer. 17–37% of patients with distant relapses have bone only metastases.

• Patients with bone predominant disease more often have hormone receptor-positive tumours.

• Endocrine therapy for bone metastasis of breast cancer is prefered to chemotherapy in the majority of cases, except especially visceral metastasis or rapidly progressive, symptomatic disease and resistant disease to endocrine therapies.

• When endocrine options have been exhausted or the patient develops more aggressive disease, chemotherapy is performed in treatment of bone predominant metastatic breast cancer. However, most effective regimen has not been defined. Single-agent oral chemotherapy (capecitabine, vinorelbine) is a widely used choice.

• Novel targeted agents and drug delivery system in management of bone metastasis are currently being evaluated in clinical trials.

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Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

This manuscript was not funded.