title: Diabetes in relation to breast cancer relapse and all-cause mortality in elderly breast cancer patients: a FOCUS study analysis.
abstract: BACKGROUND
  In developed countries, 40% of breast cancer patients are >65 years of age at diagnosis, of whom 16% additionally suffer from diabetes. The aim of this study was to assess the impact of diabetes on relapse-free period (RFP) and overall mortality in elderly breast cancer patients.
  
  
  METHODS
  Patients were selected from the retrospective FOCUS cohort, which contains detailed information of elderly breast cancer patients. RFP was calculated using Fine and Gray competing risk regression models for patients with diabetes versus patients without diabetes. Overall survival was calculated by Cox regression models, in which patients were divided into four groups: no comorbidity, diabetes only, diabetes and other comorbidity or other comorbidity without diabetes.
  
  
  RESULTS
  Overall, 3124 patients with non-metastasized breast cancer were included. RFP was better for patients with diabetes compared with patients without diabetes (multivariable HR 0.77, 95% CI 0.59-1.01), irrespective of other comorbidity and most evident in patients aged ≥75 years (HR 0.67, 95% CI 0.45-0.98). The overall survival was similar for patients with diabetes only compared with patients without comorbidity (HR 0.86, 95% CI 0.45-0.98), while patients with diabetes and additional comorbidity had the worst overall survival (HR 1.70, 95% CI 1.44-2.01).
  
  
  CONCLUSIONS
  When taking competing mortality into account, RFP was better in elderly breast cancer patients with diabetes compared with patients without diabetes. Moreover, patients with diabetes without other comorbidity had a similar overall survival as patients without any comorbidity. Possibly, unfavourable effects of (complications of) diabetes on overall survival are counterbalanced by beneficial effects of metformin on the occurrence of breast cancer recurrences.
authors.affiliation: Department of Surgery, Leiden University Medical Center, Leiden.
authors.forename: M
authors.initials: M
authors.lastname: Kiderlen
authors.forename: N A
authors.initials: NA
authors.lastname: de Glas
authors.forename: E
authors.initials: E
authors.lastname: Bastiaannet
authors.forename: C C
authors.initials: CC
authors.lastname: Engels
authors.forename: W
authors.initials: W
authors.lastname: van de Water
authors.forename: A J M
authors.initials: AJ
authors.lastname: de Craen
authors.forename: J E A
authors.initials: JE
authors.lastname: Portielje
authors.forename: C J H
authors.initials: CJ
authors.lastname: van de Velde
authors.forename: G J
authors.initials: GJ
authors.lastname: Liefers
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000401:mortality* / Q000628:therapy; D018270:Carcinoma, Ductal, Breast / Q000401:mortality* / Q000628:therapy; D015897:Comorbidity; D003924:Diabetes Mellitus, Type 2 / Q000401:mortality*; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D009364:Neoplasm Recurrence, Local / Q000401:mortality* / Q000517:prevention & control; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D012307:Risk Factors
keywords: breast cancer; diabetes; elderly; geriatric oncology; metformin; observational study