RESUMEN
Introduction: Molecular markers determined by immunohistochemistry are routinely used for predicting and prognosticating cancers including breast cancer. Molecular markers for breast cancer such as oestrogen and progesterone receptors, Her2, p53, pS2, Bcl2, EGFR, Ki67, CD34 and Cathepsin D have been used in Raja Isteri Pengiran Anak Saleha (RIPAS) Hospital. This study assessed the ethnic variations in breast cancer incidence as well as the relationships between expression of these markers with tumour stage and grade and patient survival in Brunei Darussalam . Materials and Methods: Records of breast cancer patients between 2001 and 2009 were retrieved and abstracted from the Cancer Registry maintained by the Department of Pathology at the RIPAS Hospital. These were reviewed and analysed using appropriate statistical methods. Results: Overall, the mean age at diagnosis was 49.2 years. The incidence rate of breast cancer among Chinese (56.4 per 100,000 per year) was significantly higher than Malays (27.8) and the other ethnic groups (12.3). The expression of oestrogen and progesterone receptors and pS2 was significantly greater in the more differentiated tumours while that of Ki67 and p53 in tumours and CD34 in blood vessels within the tumour was significantly greater in the less differentiated tumours. Positivity for oestrogen receptor was significantly associated with the absence of metastases in regional lymph nodes. Expression of oestrogen and progesterone receptors in tumour cells was significantly associated with enhanced patient survival, while the detection of CD34 in blood vessels within tumours was associated with poorer survival. Survival trends seen for other markers were not statistically significant. Conclusions: The different incidence of breast cancer among the different ethnic groups merits more detailed investigation of the responsible genetic, social and environmental factors. Oestrogen and progesterone receptors and CD34 are confirmed as useful markers for prognosis among our population with breast cancer. Expression of p53, Ki67 and pS2 may also be useful. These markers will be helpful in determining treatment options and for patient education.