Cell proliferation assessed by Ki-67 immunoreactivity on formalin fixed tissues is a predictive factor for survival in prostate cancer.

Stattin P, Damber JE, Karlberg L and Bergh A.
Journal of Urology 1997, 157: 219-222.

Ki-67 immunoreactivity appears to be a valid measure of proliferation and has been related to outcome in prostate cancer in a number of studies. However until recently Ki-67 immunoreactivity could only be performed on frozen section specimens. This study examines Ki-67 immunoreactivity in formalin fixed specimens allowing retrospective analysis of Ki-67 as a prognostic marker in patients with long-term follow-up.
Ki-67 index (percentage of immunoreactive cells in a tumour) was defined for 125 patients with carcinoma of the prostate found at transurethral resection and followed by surveillance. Ki-67 index correlated with grade but only weakly with stage. Mean survival of patients with a Ki-67 index of 3 or more was less than half that of patients with a Ki-67 index less than 3 (53 verses 132 months). In a Cox multiple regression analysis for cancer-specific survival, including Ki-67 index, grade, stage, age and metastasis , Ki-67 remained an independent predictive factor.