title: Ethnic differences in survival after breast cancer in South East Asia.
abstract: BACKGROUND
  The burden of breast cancer in Asia is escalating. We evaluated the impact of ethnicity on survival after breast cancer in the multi-ethnic region of South East Asia.
  
  
  RESULTS
  Using the Singapore-Malaysia hospital-based breast cancer registry, we analyzed the association between ethnicity and mortality following breast cancer in 5,264 patients diagnosed between 1990 and 2007 (Chinese: 71.6%, Malay: 18.4%, Indian: 10.0%). We compared survival rates between ethnic groups and calculated adjusted hazard ratios (HR) to estimate the independent effect of ethnicity on survival. Malays (n = 968) presented at a significantly younger age, with larger tumors, and at later stages than the Chinese and Indians. Malays were also more likely to have axillary lymph node metastasis at similar tumor sizes and to have hormone receptor negative and poorly differentiated tumors. Five year overall survival was highest in the Chinese women (75.8%; 95%CI: 74.4%-77.3%) followed by Indians (68.0%; 95%CI: 63.8%-72.2%), and Malays (58.5%; 95%CI: 55.2%-61.7%). Compared to the Chinese, Malay ethnicity was associated with significantly higher risk of all-cause mortality (HR: 1.34; 95%CI: 1.19-1.51), independent of age, stage, tumor characteristics and treatment. Indian ethnicity was not significantly associated with risk of mortality after breast cancer compared to the Chinese (HR: 1.14; 95%CI: 0.98-1.34).
  
  
  CONCLUSIONS
  In South East Asia, Malay ethnicity is independently associated with poorer survival after breast cancer. Research into underlying reasons, potentially including variations in tumor biology, psychosocial factors, treatment responsiveness and lifestyle after diagnosis, is warranted.
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center, Utrecht, The Netherlands.
authors.forename: Nirmala
authors.initials: N
authors.lastname: Bhoo-Pathy
authors.forename: Mikael
authors.initials: M
authors.lastname: Hartman
authors.forename: Cheng-Har
authors.initials: CH
authors.lastname: Yip
authors.forename: Nakul
authors.initials: N
authors.lastname: Saxena
authors.forename: Nur Aishah
authors.initials: NA
authors.lastname: Taib
authors.forename: Siew-Eng
authors.initials: SE
authors.lastname: Lim
authors.forename: Philip
authors.initials: P
authors.lastname: Iau
authors.forename: Hans-Olov
authors.initials: HO
authors.lastname: Adami
authors.forename: Awang M
authors.initials: AM
authors.lastname: Bulgiba
authors.forename: Soo-Chin
authors.initials: SC
authors.lastname: Lee
authors.forename: Helena M
authors.initials: HM
authors.lastname: Verkooijen
mesh_terms: D001210:Asia, Southeastern / Q000453:epidemiology; D001943:Breast Neoplasms / Q000175:diagnosis / Q000208:ethnology* / Q000401:mortality* / Q000473:pathology; D005006:Ethnicity / Q000208:ethnology* / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology; D008875:Middle Aged; D009362:Neoplasm Metastasis; D016019:Survival Analysis