K _i -67/MIB-1 and Recurrence in Pituitary Adenoma

Objectives  K _i -67/MIB-1 is a marker of cellular proliferation used as a pathological parameter in the clinical assessment of pituitary adenomas, where its expression has shown utility in predicting the invasiveness of these tumors. However, studies have shown variable results when using K _i -67/MIB-1 association with recurrence. The purpose of this study is to determine if a high K _i -67/MIB-1 labeling index (LI) is predictive of recurrence in pituitary adenomas. Methods  A retrospective chart review was performed for patients undergoing pituitary adenoma resection with at least 1 year of follow-up. Additionally, systematic data searches were performed and included studies that correlated recurrence rate to K _i -67/MIB-1 LI. Our institutional data were included in a synthesis with previously published data. Results  Our institutional review included 79 patients with a recurrence rate of 26.6%. We found that 8.8% of our patients had a high K _i -67/MIB-1 LI (>3%); however, high K _i -67/MIB-1 was not associated with recurrence. The systematic review identified 244 articles and 49 full-text articles that were assessed for eligibility. Quantitative analysis was performed on 30 articles including our institutional data and 18 studies reported recurrence by level of K _i -67/MIB-1 LI. Among studies that compared K _i -67/MIB-1 ≥3 vs. <3%, 10 studies reported odds ratios (OR) greater than 1 of which 6 were statistically significant. A high K _i -67/MIB-1 had higher odds of recurrence via the pooled odds ratio (OR = 4.15, 95% confidence interval [CI]: 2.31-7.42). Conclusion  This systematic review suggests that a high K _i -67/MIB-1 should prompt an increased duration of follow-up due to the higher odds of recurrence of pituitary adenoma.