MIB1 Labeling Index as an Indicator of Chemoresponse in Carcinoma of the Breast

Abstract

In this study, we determined the extent of variation in proliferative markers and hormone receptor status in breast carcinoma between core biopsies and subsequent resections, and determined the impact of clinical and histologic parameters on such variation. We performed a paired comparison of biomarkers in 87 core biopsies and subsequent resections of breast carcinomas in patients with and without preoperative chemotherapy. The markers included estrogen receptor, progesterone receptor, Her2/neu, DNA ploidy (diploidy versus nondiploidy), DNA index (difference of > or = 0.5), and MIB1 labeling index (<15% vs. >15%). The tumor biomarkers were evaluated with standard IHC and scored by automated cellular imaging systems. The number of patients showing prominent changes were as follows: ploidy, 12; DI, 15; ER, 6; PR, 15; MIB1, 17; and Her2/neu, 15. Seventeen of 87 patients sustained a significant change in MIB1 index (above or below 15%). The patients who received chemotherapy had a larger proportion with a change in MIB1 status (P < 0.05). DI showed a similar trend, although it was not statistically significant. Of the patients with MIB1 values higher in biopsy specimens, a majority showed values to decrease below 15%. MIB1 index reduction by greater than 25% was seen in 8 of 16 (50%) cases with chemotherapy, compared with only 3 of 32 (9%) without chemotherapy. MIB1 and DNA index values postchemotherapy can be a useful measure of chemoresponse. Our study underscores the need to perform prognostic markers on both biopsy and subsequent resections, especially in the setting of preoperative chemotherapy.