MUC1 expression in primary breast cancer: the effect of tamoxifen treatment

This was a non-randomised single institution retrospective study. Forty-six banked frozen tumour specimens were obtained from a group of patients who had undergone 3 weeks of neoadjuvant treatment with tamoxifen between biops y and surgery. Fifty-one comparison specimens were randomly selected from a group of concomitantly treated primary breast cancer patients who did not receive neoadjuvant tamoxifen. Specimen selection was not based on prognost ic factors: hormone receptor status, patient age, or menopausal status. MUC 1 expression and cell cycle distribution were assessed by flow cytometry. S -phase, fraction of MUC1 positive and MUC1 negative cells were compared. A lower percentage of cells expressed MUC1 following 3-week tamoxifen treatme nt 18.2% versus 28.5% (p = 0.03, Mann-Whitney) and lower levels of MUC1 exp ression were seen following tamoxifen treatment 31,519 molecules/cell versu s 39,387 (p = 0.04, Mann-Whitney). MUC1 positive cells, irrespective of tre atment group, had a greater proportion of cells in S-phase of the cell cycl e 27.9% versus 16.8% (p = 0.0004, Mann-Whitney) and demonstrated more cases of aneuploidy 80.65% versus 42.6% (p < 0.0001). MUC1 levels in primary tum ours treated neoadjunctively with 3 weeks of tamoxifen were lower than a co mparison group which did not receive tamoxifen. MUC1 should be explored fur ther as an intermediate biomarker for assessment of treatment and prognosis .