VALUE OF IMMUNOHISTOCHEMICAL-DETERMINED ESTROGEN-RECEPTOR STATUS AND PROLIFERATIVE ACTIVITY IN BREAST-CANCER - A RETROSPECTIVE STUDY INCLUDING PATIENTS TREATED BY ENDOCRINE THERAPY AT THE TIME OF RECURRENCE

The oestrogen receptor (ER) status and the proliferative activity in b reast carcinomas have proved to be of prognostic value. Because only h alf of the ER-positive patients respond to endocrine therapy it is hyp othesized that it might be cases with positive ER status and high prol iferative activity that fail endocrine treatment. Breast cancer patien ts with advanced/disseminated disease (n = 109) were included in this study. No adjuvant systemic therapy was given, but when the patients d eveloped recurrent disease they were all treated with endocrine therap y. The ER status and the proliferative activity (expressed as the ER i ndex and MIB-1 index, respectively) were investigated retrospectively on sections from the primary tumour by immunostaining with monoclonal antibodies (anti ER-antibody and MIB-1) which are applicable on formal in-fixed, paraffin-embedded tissue after microwave pretreatment. In ER -positive tumours there was no significant difference in response to e ndocrine therapy between tumours with high proliferative activity and tumours with low proliferative activity. This study shows that prolife rative activity does not seem to predict response to endocrine therapy but indicates that proliferative activity is capable of revealing dif ferences in the disease free interval, irrespective of ER status.