Obesity leads to poor prognosis in women diagnosed with breast cancer even in early stage disease as shown in systematic literature reviews, several large-scale cohort studies and critical reviews such as the Nurse's Health study and cancer prevention study II 123456789. The women with breast cancer in the highest quartile of BMI are 2.5 times as likely to die of their disease within 5 years of diagnosis compared with women in the lowest quartile of BMI 10.

Recent in vitro experiments suggest that anti-obesity agents Orlistat may have anti-tumour activity which is likely to be due to transcriptional suppression of HER II expression 11. Orlistat, has potent anti-proliferate and apoptotic effects on breast cancer cells through its ability to block the lipogenic activity of Fatty Acid Synthetase 12. In vitro experiments also suggest that essential fatty acids such as omega-3 suppress overexpression of HER II at the transcriptional level, which, in turn, interacts synergistically with anti-HER II agents such as Traztuzumab 13. Traztuzumab is a humanized monoclonal antibody directed against the extracellular domain of the tyrosine kinase receptor HER II. Abnormalities of fatty acid metabolism in the development of breast cancer are well documented and the association between Fatty acid metabolism and HER II antagonists is being discovered REF 14. Therefore, Obesity may be the missing link between the development of breast cancer and over-expression of HER II because of its effect on essential fatty acids These findings suggest a possible association between obesity, abnormal lipid metabolism and an overexpression of HER II.

Over-expression of HER II is also associated with a poor prognosis of breast cancer as HER II over-expression playS an important role in the development, aggressive behaviour of breast cancer. Overexpression of HER II has been associated with other markers of poor prognosis of breast cancer such as cathepsin D 15.

The hypothesis we tested was that the obese women with breast cancer over-express HER II more often than their lean counterparts to account for the poor prognosis in obese women.

One hundred consecutive patients were included in this study. Their height, weight and body mass index were correlated with overexpression of HER II.

All results are summarised in table 1. Using the BMI categories of less than 25, 25–30, 30–35 and more than 35 kg/m² there is no significant trend in the proportions who are HER positive or negative within these categories Figure 1. There was also no association between oestrogen or progesterone receptor positivity and obesity or HER II over expression in premenopausal or post-menopausal women with breast cancer, Figure 1 and Table 1.

Obesity is associated with poor prognosis of breast cancer. The exact mechanism by which obesity affects the outcome of breast cancer is not fully understood. HER II overexpression is associated with poor prognosis of breast caner. The present study demonstrated that the poor outcome of breast cancer in obese patients was not due to overexpression of HER II. The present study is in concordance with another small-scale study that showed no association obesity and erbB-2 expression without the use of Fluorescence in-situ hybridisation (FISH) 16. The present study confirmed that even after FISH analysis there seem to be no association between obesity and HER II expression. These are small-scale studies, and warrant larger scale research.

The relationship between obesity and steroid hormone receptors is complex and controversial. Several relationships have been reported and refuted. Our study is in concordance with other reports, which show no reliable association between steroid hormone receptor and obesity in breast cancer patients.