Skeletal related events, bone metastasis and survival of prostate cancer: a population based cohort study in Denmark (1999 to 2007)

Purpose: We describe mortality in patients with prostate cancer with and without bone metastasis further characterized by skeletal related events.

Materials and methods: We performed a cohort study of 23,087 incident patients with prostate cancer with a median 2.2-year followup identified through the Danish National Patient Registry from 1999 to 2007. We estimated the cumulative incidence of bone metastasis and skeletal related events, and described survival using the Kaplan-Meier method. Based on a Cox proportional hazard model we estimated mortality rate ratios and associated 95% CIs comparing mortality rates between patients by bone metastasis with and without skeletal related events, adjusting for age and comorbidity.

Results: Of the patients 569 (almost 3%) presented with bone metastasis at prostate cancer diagnosis, of whom 248 (43.6%) experienced a skeletal related event during followup. Of the 22,404 men (97% overall) without bone metastasis at diagnosis 2,578 (11.5%) were diagnosed with bone metastasis and 1,329 (5.9%) also experienced a skeletal related event during followup. One and 5-year survival was 87% and 56% in patients with prostate cancer without bone metastasis, 47% and 3% in those with bone metastasis, and 40% and less than 1% in those with bone metastasis and skeletal related events, respectively. Compared with men with prostate cancer without bone metastasis the adjusted 1-year mortality rate ratio was 4.7 (95% CI 4.3-5.2) in those with bone metastasis and no skeletal related events, and 6.6 (95% CI 5.9-7.5) in those with bone metastasis and a skeletal related event.

Conclusions: Bone metastasis and skeletal related events predict poor prognosis in men with prostate cancer.