Despite WHO grade 1 meningiomas are suggested to be benign tumors, there is a high proportion of recurrences in the long-term follow-up. The present study aims to establish a pragmatical scoring by analyzing clinical, radiomic, and histopathological characteristics.

We included 302 sporadic WHO grade 1 cranial meningioma patients who underwent surgery in our center from 2011 to 2021. Inclusion criteria were age ≥ 18 years, primary case, sporadic tumor, available imaging as follow-up data. Radiomic shape features, MIB-1 index data, extent of resection, and patient-specific characteristics were assessed. Statistical analyses were performed using R studio (RStudio, Boston, MA, USA) with the R package Survminer. Based on the Cox regression analysis of meningioma progression a scoring system was developed.

Twenty-four (7.9%) patients had a local tumor progression. Multivariable Cox regression analysis revealed that MIB-1 Index ≥5% (HR: 4.1, 95%CI: 1.5-11.5), age ≤54 (HR: 2.7, 95%CI: 1.1-6.7), and Simpson grade ≥III (HR:2.9, 95%CI: 1.1-8.1) were independently associated with meningioma recurrence and were included in the final score, which assigns 1 point for age ≤ 54 years, 1.5 points for Simpson grade ≥ III, and 2 points for MIB-1 ≥ 5%. The rate of meningioma recurrence per 100 patient-years was 0.098 in patients with a score of ≤1.5 (low risk), 0.30 in patients with a score between 1.5 and 3 points (intermediate risk), and 0.91 in patients with a score ≥3.0 (high risk). The mean times to recurrence of patients in the low-risk group, intermediate risk group, and high-risk group was 145.5 months (95% CI: 137.1-153.8), 114.7 months (95% CI: 100.1-129.4), and 71.0 months (49.0-93.1), respectively (p < 0.001). Compared to low-risk patients, the risk of WHO grade 1 meningioma recurrence was significantly higher in intermediate-risk (HR: 3.2, 95% CI: 1.2-8.5) and high-risk (HR: 11.0, 95% CI: 4.1-29.5). The area under curve of the score was 0.73 (95% CI: 0.61-0.84).

The proposed SAM-score can assist in the identification of patients with sporadic cranial WHO grade 1 meningiomas at increased risk for tumor recurrence.