The Ki-67 Proliferation Index as a Marker of Time to Recurrence in Intracranial Meningioma

BACKGROUND: There are examples of incongruence between the WHO grade and clinical course in meningioma patients. This incongruence between WHO grade and recurrence has led to search for other prognostic histological markers. OBJECTIVE: To study the correlation between the Ki-67 proliferative index (PI), risk of recurrence, and recurrence rates in meningioma patients. METHODS: We prospectively collected pathological diagnosis of de novo consecutive meningiomas. In total, we followed 159 patients with clinical controls until recurrence, death, or emigration. We estimated the correlation between risk of recurrence and Ki-67 PI when adjusted for age at diagnosis, sex, WHO grade, extent of surgical resection, and tumor location. We estimated the cumulative incidence of recurrence when considering death without recurrence a competing risk. We report recurrence rates per 100 person-years. RESULTS: A 1%-point increase of Ki-67 PI yielded a hazard ratio of 1.12 (95% CI:1.01-1.24) in a multivariate analysis. The cumulative incidence of recurrence was 3% for Ki-67 0% to 4% vs 19% for Ki-67 > 4% meningiomas after 1 yr, but 24% vs 35%, respectively, after 10 yr. There was no significant difference in mean Ki-67 P1 between nonrecurrent and recurrent meningioma in a 2-sample t-test (P = .08). The strongest relationship was detected between Ki-67 PI and time to recurrence: Ki-67 , 4% meningiomas recurred after median 4.8 yr, compared to 0.60 to 0.75 yr for patients with higher Ki-67 PI. CONCLUSION: Ki-67 PI was a marker for time to recurrence rather than a predictor of recurrence. Ki-67 PI may be utilized for patient tailored follow-up.