Variation of hormonal receptor, pS2, c-erbB-2 and GSTpi contents in breast carcinomas under tamoxifen: a study of 74 cases.

Seventy-four post menopausal patients with primary non-metastatic invasive ductal carcinomas of the breast were first treated with tamoxifen alone (30 mg p.o. daily) for 5 months. To study changes induced by tamoxifen, core biopsies before treatment and surgical specimens after hormonal therapy were assayed by immunohistochemistry for oestrogen (ER) and progesterone receptors (PR), pS2, GSTpi and c-erbB2. After tamoxifen, ER and PR significantly decreased in 60 and 44 cases respectively, whereas 11 and 19 cases showed no variation and 2 and 11 cases showed an increase (P<10(-4)). GSTpi and pS2 showed a significant increase in 43 and 41 cases, a decrease in 2 and 21 cases and no variation in 29 and 12 cases (P<10(-4) and P=0.04 respectively). c-erbB-2 showed no significant variation under tamoxifen, increased in only three cases and decreased in 13 cases. No relation was found between these variations and efficiency of hormone therapy. Our results allow a better knowledge of protein expression modifications occurring in breast cancer cells under tamoxifen therapy. They are also more consistent with clone selection rather than with phenotype modification.