Article Text

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
  1. Karynsa Cetin1,
  2. Christian Fynbo Christiansen2,
  3. Claus Sværke2,
  4. Jacob Bonde Jacobsen2,
  5. Henrik Toft Sørensen2
  1. 1Center for Observational Research, Amgen Inc., One Amgen Center Drive, Thousand Oaks, California, USA
  2. 2Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark
  1. Correspondence to Karynsa Cetin; karynsah{at}amgen.com

Abstract

Objectives 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).

Setting Denmark.

Participants 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.

Primary and secondary outcome measures 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.

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/

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