title: Incidence of bone metastases in breast cancer patients in the United Kingdom: results of a multi-database linkage study using the general practice research database.
abstract: BACKGROUND
  Bone is a frequent site for metastases among women with breast cancer. We conducted a study using the General Practice Research Database (GPRD), with linkage to the National Cancer Registry (NCR) and Hospital Episode Statistics (HES), to estimate the incidence of bone metastases in women with breast cancer in the United Kingdom.
  
  
  METHODS
  We identified all women in the GPRD aged 20-99 with a first-time diagnosis of breast cancer between 2000 and 2006. To address potential underreporting, we developed and validated an algorithm to serve as a proxy for bone metastases. Bone metastases were defined as (1) a bone cancer diagnosis code on the same day or following breast cancer diagnosis date, or (2) another metastasis code plus codes consistent with bone metastases diagnosis or treatment using the algorithm. We sent questionnaires to a sample of general practitioners to validate these definitions.
  
  
  RESULTS
  We included 13,207 breast cancer patients (median age at diagnosis of 61 years) who contributed 70,885 person-years of follow-up. The majority of patients had stage 1 or 2 breast cancer (90.4%), and 2.6% had metastatic breast cancer at diagnosis. We identified 788 women (6.0%) with bone metastases after a median follow-up of 5.4 years. Questionnaire results validated the diagnosis of bone metastases in 88% of patients with a bone cancer code and for 70% identified with the algorithm.
  
  
  CONCLUSIONS
  This is the first time the GPRD has been linked to HES and NCR to study the epidemiology of bone metastases, adding important information on the burden of bone metastasis.
authors: Boston Collaborative Drug Surveillance Program, Boston University School of Medicine, 11 Muzzey Street, Lexington, MA 02421, USA. khagberg@bu.edu
authors: Katrina Wilcox
authors: KW
authors: Hagberg
authors: Aliki
authors: A
authors: Taylor
authors: Rohini Khorana
authors: RK
authors: Hernandez
authors: Susan
authors: S
authors: Jick
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001859:Bone Neoplasms / Q000453:epidemiology* / Q000556:secondary*; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000473:pathology*; D016208:Databases, Factual; D005260:Female; D058006:General Practice / Q000706:statistics & numerical data; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D012042:Registries; D011795:Surveys and Questionnaires; D006113:United Kingdom / Q000453:epidemiology; D055815:Young Adult