Survival in patients with breast cancer with bone metastasis: a Danish population-based cohort study on the prognostic impact of initial stage of disease at breast cancer diagnosis and length of the bone metastasis-free interval.
OBJECTIVE
Since population-based data on prognostic factors affecting survival in patients with breast cancer with bone metastasis (BM) are currently limited, we conducted this nationwide retrospective cohort study to examine the prognostic role of disease stage at breast cancer diagnosis and length of BM-free interval (BMFI).


METHODS
Denmark.


METHODS
2427 women with a breast cancer diagnosis between 1997 and 2011 in the Danish Cancer Registry and a concurrent or subsequent BM diagnosis in the Danish National Registry of Patients.


METHODS
Survival (crude) based on Kaplan-Meier method and mortality risk (crude and adjusted for age, year of diagnosis, estrogen receptor status and comorbidity) based on Cox proportional hazards regression analyses by stage of disease at breast cancer diagnosis and by length of BMFI (time from breast cancer to BM diagnosis), following patients from BM diagnosis until death, emigration or until 31 December 2012, whichever came first.


RESULTS
Survival decreased with more advanced stage of disease at the time of breast cancer diagnosis; risk of mortality during the first year following a BM diagnosis was over two times higher for those presenting with metastatic versus localised disease (adjusted HR=2.12 (95% CI 1.71 to 2.62)). With respect to length of BMFI, survival was highest in women with a BMFI <1 year (ie, in those who presented with BM at the time of breast cancer diagnosis or were diagnosed within 1 year). However, among patients with a BMFI ≥1 year, survival increased with longer BMFI (1-year survival: 39.9% (95% CI 36.3% to 43.6%) for BMFI 1 to <3 years and 52.6% (95% CI 47.4% to 57.6%) for BMFI ≥5 years). This pattern was also observed in multivariate analyses.


CONCLUSIONS
Stage of disease at breast cancer diagnosis and length of BMFI appear to be important prognostic factors for survival following BM.
Center for Observational Research, Amgen Inc., One Amgen Center Drive, Thousand Oaks, California, USA.
Karynsa
K
Cetin
Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark.
Christian Fynbo
CF
Christiansen
Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark.
Claus
C
Sværke
Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark.
Jacob Bonde
JB
Jacobsen
Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark.
Henrik Toft
HT
Sørensen
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001859:Bone Neoplasms / Q000401:mortality* / Q000556:secondary*; D001943:Breast Neoplasms / Q000401:mortality* / Q000473:pathology* / Q000628:therapy; D003718:Denmark; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D008875:Middle Aged; D009367:Neoplasm Staging; D011379:Prognosis; D012042:Registries; D012189:Retrospective Studies; D016019:Survival Analysis; D055815:Young Adult