Survival after bone metastasis by primary cancer type: a Danish population-based cohort study

OBJECTIVE In the 10 most common primary types with bone metastases, we aimed to examine survival, further stratifying on bone metastases only or with additional synchronous metastases. METHODS We included all patients aged 18 years and older with incident hospital diagnosis of solid cancer between 1994 and 2010, subsequently diagnosed with BM until 2012. We followed patients from date of bone metastasis diagnosis until death, emigration or 31 December 2012, whichever came first. We computed 1-year, 3-year and 5-year survival (%) and the corresponding 95% CIs stratified on primary cancer type. Comparing patients with bone metastasis only and patients with other synchronous metastases, we estimated crude and adjusted HRs and corresponding 95% CI for mortality. RESULTS We included 17 251 patients with bone metastasis. The most common primary cancer types with bone metastasis were prostate (34%), breast (22%) and lung (20%). One-year survival after bone metastasis diagnosis was lowest in patients with lung cancer (10%, 95% CI 9% to 11%) and highest in patients with breast cancer (51%, 50% to 53%). At 5 years of follow-up, only patients with breast cancer had over 10% survival (13%, 11% to 14%). The risk of mortality was increased for the majority of cancer types among patients with bone and synchronous metastases compared with bone only (adjusted relative risk 1.29-1.57), except for cervix, ovarian and bladder cancer. CONCLUSIONS While patients with bone metastases after most primary cancers have poor survival, one of ten patients with bone metastasis from breast cancer survived 5 years.