The effect of tamoxifen on breast tumour vascularity

As there is experimental evidence to suggest that tamoxifen may exert an an ti-angiogenic effect, the present study was designed to investigate the eff ect of primary tamoxifen on breast tumour angiogenesis. Fifty seven patient s with large operable primary breast cancers were treated with tamoxifen (2 0 mg daily) for between three and six months prior to definitive surgery. C linical response to treatment was assessed by serial ultrasound measurement s of tumour volume and a responding tumour was defined as one in which ther e was a greater than 25% reduction in volume at the end of treatment. Patie nts underwent a wedge biopsy at diagnosis and definitive surgery on complet ion of tamoxifen, thus providing tumour sections before and after treatment . Microvessel counts (mvc) were performed following staining with the endot helial cell marker, antibody to Factor VIII, and changes in mvc were correl ated with response. Forty three of 57 patients had tumours that responded to tamoxifen. There w as no difference in pre-treatment mvc between non-responding and responding tumours. Post-treatment mvc was significantly higher in non-responding tha n responding tumours. There was a significant reduction in mvc in respondin g tumours following treatment with tamoxifen, and a significant increase in mvc was detected in non-responding tumours. A significant correlation was demonstrated between percentage change in mvc and percentage reduction in t umour volume. This is the first study to demonstrate a reduction in breast cancer angiogenesis in tumours that have responded to primary tamoxifen in the clinical setting.