P4-16-07: Breast Cancer Bone Metastasis Prevalence and Survival Outcomes: A Quantitative Review of the Literature.
Authors: Mitchell ME , Taylor A , Lowe KA , Langeberg W , Alexander D , Kelsh M , Body J-J 
Published: June 2012

Background

Bone metastases are common in breast cancer patients and an important cause of morbidity and mortality. This review provides the first systematic and quantitative summary of the proportion of breast cancer patients with bone metastasis and their survival, presented by stage at diagnosis and length of follow-up.

Materials and methods: A literature review was conducted using PubMed to identify full-text studies published in English 1999–2009. Studies were included if they had ≥100 adult patients with Stage I-IV breast cancer and were generalizable to the overall breast cancer population. The design and intent of included studies varied, including clinical trials of bone-targeted therapies and observational studies of cancer patients evaluating staging techniques, biomarkers, and other factors. To improve homogeneity, studies were grouped by stage at diagnosis, whether follow-up for bone metastases occurred, and the clinical point at which the proportion of patients with bone metastasis was estimated (e.g., at initial staging). Studies reporting survival were only included in quantitative summaries if survival was measured from the date of bone metastasis diagnosis. With regard to clinical trials of bisphosphonates, only proportion and survival data from the placebo group were utilized since the goal was to describe bone metastasis among patients untreated with bone-targeted therapy. Meta-analytic techniques were applied to (1) proportion data using random effects models to calculate weighted averages, and (2) survival data using an average of reported median survivals. Various sensitivity analyses were also conducted.

Results: Nineteen studies were included in our quantitative summary of proportion data. At initial staging of breast cancer, 7% (N=2; 95% confidence interval [CI]=5-9%) of all patients had bone metastases and 69% (N=2; 95% CI=47-85%) of Stage IV patients had bone metastases. Among breast cancer patients followed from the diagnosis of Stage I-III breast cancer, 10% (N=6; 95% CI=6-15%) had bone metastases after a median follow-up &lt;10 years, compared to 24% (N=3; 95% CI=19-31%) after a median follow-up ≥10 years. Twelve studies were included in our quantitative summary of survival data. Survival was longer among patients with metastases solely in bone (N=7; average median=30 months), compared to patients with bone metastases and metastases at other sites (N=5; 23 months) and patients with metastases only at sites other than bone (N=3; 9 months).

Discussion: Significant heterogeneity across studies was observed, reflecting the variability in study populations, locations, and other factors. Despite this and other limitations (e.g., few studies in some categories), this represents the first analysis of the literature to quantify the prevalence and survival of bone metastasis in breast cancer. Our results indicated that bone is a site of metastasis among more than 50% of Stage IV patients at diagnosis of breast cancer. Median survival among breast cancer patients with metastases located solely in the bone is at least six months longer compared to those with metastases at multiple sites (including bone) and sites other than bone.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-16-07.