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.