PCNA and Ki-67 labelling indices in pre-irradiated and post-irradiated astrocytomas: a comparative immunohistochemical analysis for evaluation of proliferative activity

Aim-To determine the tumour proliferative activity in a series of archival cerebral astrocytomas and compare proliferating cell nuclear antigen (PCNA) and Ki-67 labelling indices in the primary and recurring neoplasms following therapeutic radiation. Method-Twenty eight cases of preirradiated and post-irradiated astrocytomas (ranging from WHO grades I to IV) were stained immunohistochemic ally using the avidin-biotin horseradish peroxidase technique. Two antibodies, PC10 and MIB-1, were used to establish the proliferating labelling indices. PC10 identifies PCNA and MIB-1 recognises the Ki-67 antigen. Results-Both antibodies showed significantly higher labelling indices in the post-irradiated specimens. However, in general, the Ki-67 indices were lower than those for PCNA. MIB-1 immunoreactivity showed less variation and was more intense than that seen with PC10. The discrepancy between the labelling indices of the pre-irradiated and post-irradiated samples raises questions about the evolution of astrocytomas and the effects of therapeutic intervention. Conclusions-The data may represent genetic alterations, the natural tumour course, and/or the effect of radiation. Although both of the antibodies reflected the state of growth of neoplastic cells in astrocytomas, MIB-1 was more reliable. A simple immunohistochemical method using proliferation markers does have an important role in the future care of patients with astrocytoma.