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

Background: 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. Methods: 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. Results: 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. Conclusions: 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.