Lack of prognostic effect of Cox-2 expression in primary breast cancer on short-term follow-up

Aims: Cyclo-oxygenase (Cox) catalyses the conversion of arachidonic acid into prostaglandins (PG) and other eciosanoids. The prostaglandins, especially PGE2 are implicated in tumorigenesis via angiogenesis and suppression of immune reactivity. There are two known isoforms of the enzyme, Cox-1, which is constitutively expressed and the inducible isoform, Cox-2. Cox-2 is induced in response to inflammatory mediators, growth factors, oncogenes and mitogens. Non-selective Cox inhibitors may reduce the relative risk of colonic and breast carcinoma. Methods: We studied the expression of Cox-2 by immunohistochemistry in 106 primary breast carcinoma specimens collected over a three-year period, using a commercially available polyclonal antibody on formalin-fixed, paraffin-embedded tissue. The slides were examined independently by two pathologists. Tumours were classified according to accepted criteria and an immunohistochemical score (IHS) was calculated for each specimen. The IHS combines the percentage of immunoreactive cells (quantity score) and an estimate of staining intensity (staining intensity score). Results: All patients were female. The mean age was 53 years, range 28–86 years. Forty percent (n=42) of tumours were node negative and 60% (n=64) node positive. Forty-nine percent (n=52) of tumours were grade 3, a further 49% (n=52) grade 2 and 2% (n=2) grade 1. There was no statistically significant correlation between IHS and tumour size, grade, histology, nodal status, estrogen receptor or progesterone receptor positivity. A trend was observed showing an IHS of zero is associated with prolonged survival compared with an IHS of 9–12. Conclusion: Cox-2 expression in primary breast cancer does not correlate with accepted pathological or biochemical prognostic indicators.