Ki-67 immunolabelling index is a prognostic indicator in childhood posterior fossa ependymomas

Conventional histological evaluation and subclassification of childhood epe ndymomas poorly predict their biological behaviour. The Ki-67 labelling ind ex (Ki-67 LI), a measure of growth fraction, correlates with the biological behaviour of several neoplasms, and this retrospective study tested the hy pothesis that Ki-67 LI is a prognostic indicator in childhood posterior fos sa ependymomas. Immunocytochemistry using an antibody to Ki-67 was undertak en on 5 mu m sections of formalin-fixed, paraffin-embedded tissue from 74 c ases of childhood (age <16 years.) posterior fossa ependymoma, A Ki-67 LI w as established by counting the proportion of labelled nuclei in more than 1 000 cells from several histological fields. Several clinical and histologic al variables (including Ki-67 LI) potentially associated with survival were entered into univariate and multivariate analyses using a Cox proportional hazards model. Variables that showed a significant and independent associa tion with survival were Ki-67 LI (P < 0.002), whether total surgical resect ion lad bean achieved according to operation records (P < 0.03), and whethe r no adjuvant therapy had been given (P < 0.01). Age, sex, and the presence of necrosis or microvascular proliferation did not correlate with survival , In our defined population of patients with ependymomas, Ki-67 LI is a str ong prognostic indicator, We recommend that Ki-67 LI is used in the histolo gical evaluation of childhood posterior fossa ependymomas during trials of novel adjunctive therapies.