The incidence of atypical femoral fractures in breast cancer patients with bone metastases who received bisphosphonate treatment

Bone metastases

Bone is the most frequent site for metastasis for many cancers, notably for tumours originating in the breast and the prostate. Tumour cells can escape from the primary tumour site and colonize the bone microenvironment. Within the bone, these disseminated tumour cells, as well as those arising in the context of multiple myeloma, may assume a state of dormancy, remaining quiescent for years before resuming proliferation and causing overt metastasis, which causes bone destruction via activation of osteoclast-mediated osteolysis. This structural damage can lead to considerable morbidity, including pain, fractures and impaired quality of life. Although treatment of bone metastases and myeloma bone disease is rarely curative, disease control is often possible for many years through the use of systemic anticancer treatments on a background of multidisciplinary supportive care. This care should include bone-targeted agents to inhibit tumour-associated osteolysis and prevent skeletal morbidity as well as use of appropriate local treatments such as radiation therapy, orthopaedic surgery and specialist palliative care to minimize the impact of metastatic bone disease on physical functioning. In this Primer, we provide an overview of the clinical features, the pathophysiology and the specific treatment approaches to prevent and treat bone metastases from solid tumours as well as myeloma bone disease.

Long-term impact of bone-modifying agents for the treatment of bone metastases: a systematic review

PURPOSE

Bone-modifying agents (BMAs) for bone metastases are commonly prescribed for many years even though randomized clinical trials are only 1-2 years in duration. A systematic review on the risk-benefit of BMA use for > 2 years in breast cancer or castrate-resistant prostate cancer was conducted.

METHODS

MEDLINE, Embase, and Cochrane databases were searched (1970-February 2019) for randomized and observational studies, and case series reporting on BMA efficacy (skeletal-related events and quality of life) and toxicity (osteonecrosis of the jaw, renal impairment, hypocalcemia, and atypical femoral fractures) beyond 2 years.

RESULTS

Of 2107 citations, 64 studies were identified. Three prospective and 9 retrospective studies were eligible. Data beyond 2 years was limited to subgroup analyses in all studies. Only one study (n = 181) reported skeletal-related event rates based on bisphosphonate exposure, with decreased rates from 27.6% (0-24 months) to 15.5% (> 24 months). None reported on quality of life. All 12 studies (denosumab (n = 948), zoledronate (n = 1036), pamidronate (n = 163), pamidronate-zoledronate (n = 522), ibandronate (n = 118)) reported ≥ 1 toxicity outcome. Seven bisphosphonate studies (n = 1077) and one denosumab study (n = 948) reported on osteonecrosis of the jaw. Across three studies (n = 1236), osteonecrosis of the jaw incidence ranged from 1 to 4% in the first 2 years to 3.8-18% after 2 years. Clinically significant hypocalcemia ranged from 1 to 2%. Severe renal function decline was ≤ 3%. Atypical femoral fractures were rare.

CONCLUSIONS

Evidence informing the use of BMA beyond 2 years is heterogeneous and based on retrospective analysis. Prospective randomized studies with greater emphasis on quality of life are needed.

PROSPERO REGISTRATION NUMBER

CRD42019126813.