Treatment and survival of Asian women diagnosed with breast cancer in New Zealand

PurposeThis study aims to examine the differences in characteristics, treatment and survival between Asian and European women diagnosed with stage I-III breast cancer in New Zealand.MethodsThe studied population included European women and Asian women diagnosed with stage I-III breast cancer between June 2000 and May 2013 identified from the combined Waikato and Auckland Breast Cancer Registers. Characteristics and treatment were compared between Asian and European women. Kaplan-Meier method was used to examine the survival difference. Cox proportional hazards model was used to estimate the hazard ratio (HR) of mortality.ResultsThe studied cohort included 8608 European and 949 Asian women. Asian women were younger, had less comorbidities and were less likely to be obese than European women. Asian women were more likely to have grade 3, larger and HER2+ breast cancers. Asian women were more likely to receive mastectomy, less likely to have reconstruction after mastectomy, less likely to have chemotherapy, less likely to be treated with trastuzumab if HER2+, and had better adherence to endocrine therapy (adjusted odds ratio: 1.54; 95% CI 1.22-1.93). Asian women had better cancer-specific survival and all-cause survival than European women. The adjusted HR of cancer-specific mortality and all-cause mortality were 0.64 (95% CI 0.49-0.82) and 0.68 (95% CI 0.55-0.84), respectively.ConclusionsAsian women are more likely to have high grade, larger and HER2+ breast cancers than European women. In spite of this, they had better breast cancer outcomes. Possible explanations include the differences in adherence to endocrine therapy, age, BMI and comorbidities.