PCNA AND KI-67 LABELING INDEXES IN PRE-IRRADIATED AND POST-IRRADIATEDASTROCYTOMAS - A COMPARATIVE IMMUNOHISTOCHEMICAL ANALYSIS FOR EVALUATION OF PROLIFERATIVE ACTIVITY

Aim-To determine the tumour proliferative activity in a series of arch ival cerebral astrocytomas and compare proliferating cell nuclear anti gen (PCNA) and Ki-67 labelling indices in the primary and recurring ne oplasms following therapeutic radiation. Method-Twenty eight cases of preirradiated and post-irradiated astrocytomas (ranging from WHO grade s I to IV) were stained immunohistochemic ally using the avidin-biotin horseradish peroxidase technique. Two antibodies, PC10 and MIB-1, wer e used to establish the proliferating labelling indices. PC10 identifi es PCNA and MIB-1 recognises the Ki-67 antigen. Results-Both antibodie s showed significantly higher labelling indices in the post-irradiated specimens. However, in general, the Ki-67 indices were lower than tho se for PCNA. MIB-1 immunoreactivity showed less variation and was more intense than that seen with PC10. The discrepancy between the labelli ng indices of the pre-irradiated and post-irradiated samples raises qu estions about the evolution of astrocytomas and the effects of therape utic intervention. Conclusions-The data may represent genetic alterati ons, the natural tumour course, and/or the effect of radiation. Althou gh both of the antibodies reflected the state of growth of neoplastic cells in astrocytomas, MIB-1 was more reliable. A simple immunohistoch emical method using proliferation markers does have an important role in the future care of patients with astrocytoma.