Initiation of bone-targeted agents in patients with bone metastases and breast or castrate-resistant prostate cancer actively treated in routine clinical practice in Europe

Guidelines recommend starting bone-targeted agents (BTA), such as zoledronic acid and denosumab, as soon as bone metastases (BMs) are definitively diagnosed in all patients with breast cancer (BC) or castration-resistant prostate cancer (CRPC) whether they are symptomatic or not. Data were analyzed from 1364 patients with BC and 1161 patients with CRPC who had BMs and were receiving anti-cancer therapy in hospitals across six European countries (Belgium, France, Germany, Italy, Spain and the UK). The 731 physicians (medical oncologists or urologists) provided insights in the decision-making factors driving their management of bone health for these patients, and the patient medical records indicated how these decisions were reflected in routine clinical practice. Within three months of a BM diagnosis, 74% of BC and 51% of CRPC patients had initiated treatment with a BTA. Around 12% of BC and 23% of CRPC patients did not receive a BTA following BM diagnosis. Irrespective of the tumour type (BC or CRPC), most physicians prescribed either denosumab or zoledronic acid as first BTA therapy. Physicians reported bone pain as a major decision-making factor to initiate a BTA. The presence of bone complications at BM diagnosis and bone pain at BM diagnosis were found to be significant predictive factors for a BTA initiation, irrespective of tumour type. Despite European Society for Medical Oncology (ESMO) guidance on bone protection irrespective of symptomatic disease, not all patients with BMs received a BTA following a BM diagnosis. This suggests that clinical judgements and patients' communication of their pain to their physicians contributed to the decision to prescribe bone protection therapy in cancer patients. •Not all patients with cancer and bone metastasis receive bone-targeted agents.•Diagnosis of a bone metastasis alone does not result in bone protection therapy.•Bone pain appears to trigger bone-targeted agent initiation.•Bone-targeted agents were underused in castrate-resistant prostate cancer patients.•Guideline recommendations are not always implemented in routine clinical practice.