EPIDEMIOLOGY Differences in breast cancer biological characteristics between ethnic groups in New Zealand

Objective To investigate differences in breast cancer biological characteristics between ethnic groups in Auckland, New Zealand. Design Prospective cohort study. Setting Auckland Breast Cancer Study Group. Participants All people diagnosed with breast cancer in the greater Auckland area between 2000 and 2005 who agreed to participate (1,577). Main outcome measures Size, grade, lymph node status, estrogen receptor (ER), progesterone receptor (PR), lymphovascular invasion (LVI), grade allowing for size, all compared with ethnicity. Results NZ Maori and Pacific Island participants had larger tumours (P \ 0.0001), higher grade tumours (P \ 0.0001) with more involved lymph nodes (P \ 0.0001). When allowing for size, there was still an indication that NZ Maori people had higher grade tumours (P = 0.03). There was no difference in ER, PR and LVI between ethnic groups. Conclusion These data suggest differences in tumour biology related to ethnicity in the Auckland population and this has implications for breast cancer screening and management.