Incidence of distal bone metastases in patients treated for palliative radiotherapy and associations with primary tumour types

PURPOSE: This study assesses the incidence of distal bone metastases in palliative radiotherapy (RT) patients. MATERIAL AND METHODS: All courses of RT for bone metastases from 2007–2011 for patient living in British Columbia (BC) were identified in a provincial RT programme. Treated bone metastases (BoM) were categorized as distal if the BoM was located within or distal to the elbow or knee. Patients were grouped by primary tumour site as breast, lung, prostate gastrointestinal, haematological, melanoma, and other. The incidence of distal bone metastases and associations with primary tumour types were determined. RESULTS: From 2007 to 2011, 8008 patients were treated with 16,277 courses of RT, of which 425 (3%) were courses of RT for distal BoM. The incidence of distal BoM in decreasing order by primary tumour type was melanoma (5%), haematological (3%), lung (2%), other (2%), prostate (2%), breast (1%) and gastrointestinal (1%). Distal BoM where more commonly identified in the lower extremity (87%, p<0.001). Single fraction RT was used more commonly for distal vs non-distal BoM (66% vs. 49%; p<0.001). CONCLUSION: The incidence of distal BoM among patients treated with palliative RT was 3% and most commonly identified in patients with melanoma and haematological malignancies.