Apparent lack of prognostic value of MIB-1 index in anal carcinomas treated by radiotherapy

Abstract

This study was conducted to investigate the influence of Mib-1 index on outcome in 55 patients with T1-4 anal carcinomas treated radically by radiotherapy (RT) alone (24) or by concomitant chemo-radiotherapy (31). Median follow-up for surviving patients was 94 months (range 17-179 months). Tissue materials were obtained from pretreatment biopsies. A modified immunoperoxidase technique consisting of microwave heating of routinely processed material was employed using the Mib-1 antibody (Immunotech, 1:50). The median Mib-1 index for all patients was 53% (range 18-96%). Subgroups of patients with high vs low Mib-1 indices (separated by the median value) had statistically similar outcomes regarding 5-year overall survival (64% vs 65% P = 0.7), locoregional control (77% vs 69%, P = 0.5) and disease-free survival (73% vs 66%, P = 0.5). Moreover, no significant association was found between mean Mib-1 indices and various clinicopathological parameters studied (age, sex, circumferential tumour extent, T-stage, N-stage and histological type). In conclusion, Mib-1 index failed to predict the outcome of patients with anal carcinomas treated conservatively by radiotherapy with or without chemotherapy. It is noteworthy that the median Mib-1 index observed in anal carcinomas in this study was among the highest yet reported for cancers of epithelial origin.