MIB-1 is used in clinical applications to determine the Ki-67 labelling index (A measure of the mitotic activity of a cell population, defined as the number of cells in the S phase of the growth cycle divided by the total cells in the population). One of its primary advantages over the original Ki-67 antibody (and the reason why it has essentially supplanted the original antibody for clinical use) is that it can be used on formalin fixed paraffin embedded sections, after heat-mediated antigen retrieval.

The MIB-1 index can differentiate tumors with a high risk of recurrence, which could be beneficial for planning tailored optimal follow-up strategies ¹⁾.

Endo et al., reviewed 45 patients with atypical meningioma who underwent surgical intervention between January 2000 and December 2013. The mean age of the patients and mean follow-up period was 58.7 years and 81.0 months, respectively. Analyses included factors such as patient age, gender, location and size of tumor, extent of surgical resection (Simpson Grading System), and MIB-1 index (LI). Univariate analysis was used to detect prognostic factors associated with recurrence and survival.

The 5-year recurrence-free rate for all 45 patients was 58.4 %; 5- and 10-year survival rates were 83.2 % and 79.9 %, respectively. In univariate analyses, age >60 years, and MIB-1 LI correlated with disease recurrence, whereas age >60 years, subtotal surgical resection, MIB-1 LI, and indication for radiotherapy correlated with death. MIB-1 LI levels higher than 12.8 % and 19.7 % predicted recurrence and death, respectively. In our cohort, 26 patients received postoperative radiotherapy including conventional radiation (n = 21) or gamma knife radiosurgery (n = 5). Postoperative radiotherapy did not decrease recurrence rates in our cohort (p = 0.63). Six and two patients who died during the study period underwent conventional radiation and radiosurgery, respectively.

Age, male gender, extent of surgical resection, and higher MIB-1 LI influenced the outcome of atypical meningioma. In this cohort, postoperative radiotherapy failed to provide long-term tumor control. Following incomplete surgical resection of atypical meningioma in elderly patients, adjuvant postoperative radiotherapy may not be an ideal treatment option, particularly when MIB-1 LI is higher than 19.7 % ²⁾.

A total of 240 patients harboring 248 benign meningiomas were included in a study. Simpson Grade IV resection was associated with a significantly shorter RFS than Simpson Grade I, II, or III resection (p<0.001), while no statistically significant difference was noted in RFS between Simpson Grades I, II, and III. Among meningiomas treated by Simpson Grade II and III resections, however, multivariate analysis revealed that an MIB-1 index of 3% or higher was associated with a significantly shorter time to recurrence.

The clinical significance of the different management strategies related to Simpson Grade I-III resection may have been diluted in the modern surgical era. The MIB-1 index can differentiate tumors with a high risk of recurrence, which could be beneficial for planning tailored optimal follow-up strategies. The results of this study appear to provide a significant backing for the recent shift in meningioma surgery from attempting aggressive resection to valuing the quality of the patient's life ³⁾.

A total of 113 asymptomatic meningiomas were analyzed by fine volumetry. A comparison of growth rates and patterns between incidental skull base meningiomas and non-incidental skull base meningiomas was made. Subsequently, materials obtained from 210 patients with symptomatic meningiomas who were treated in the authors' hospital during the same period were included for a biological comparison between skull base and non-skull base tumors using the MIB-1 index.

The 110 patients with IDMs included 93 females and 17 males, with a mean follow-up period of 46.9 months. There were 38 skull base (34%) and 75 non-skull base (66%) meningiomas. Forty-two (37%) did not exhibit growth of more than 15% of the volume, whereas 71 (63%) showed growth. Only 15 (39.5%) of 38 skull base meningiomas showed growth, whereas 56 (74.7%) of 75 non-skull base meningiomas showed growth (p = 0.0004). In the 71 IDMs (15 skull base and 56 non-skull base), there was no statistical difference between the 2 groups in terms of mean age, sex, follow-up period, or initial tumor volume. However, the percentage of growth (p = 0.002) was significantly lower and the doubling time (p = 0.008) was significantly higher in the skull base than in the non-skull base tumor group. In subsequently analyzed materials from 94 skull base and 116 non-skull base symptomatic meningiomas, the mean MIB-1 index for skull base tumors was markedly low (2.09%), compared with that for non-skull base tumors (2.74%; p = 0.013).

Skull base IDMs tend not to grow, which is different from non-skull base tumors. Even when IDMs grow, the rate of growth is significantly lower than that of non-skull base tumors. The same conclusion with regard to biological behavior was confirmed in symptomatic cases based on MIB-1 index analyses. The authors' findings may impact the understanding of the natural history of IDMs, as well as strategies for management and treatment of IDMs and symptomatic meningiomas ⁴⁾.