Proposed novel classification of circumscribed Lower-Grade Gliomas (cLGG) vs. infiltrating Lower-Grade Gliomas (iLGG): Correlations of radiological features and clinical outcomes

Purpose: We hypothesize that lower grade gliomas (LGG) can be identified and classified into two distinct subtypes: radiologically circumscribed Lower-Grade Gliomas (cLGG) and infiltrating Lower-Grade Gliomas (iLGG) based on radiological parameters and that these two different subtypes behave differently in terms of clinical outcomes. Methods: We conducted a retrospective cohort study on surgical patients diagnosed with lower grade glioma over five years. Patient records and MRIs were reviewed, and neurosurgeons classified tumors into cLGG and iLGG groups. Results: From the 165 patients in our cohort, 30 (18.2%) patients were classified as cLGG and 135 (81.8%) patients were classified as iLGG Mean age in cLGG was 31.4 years while mean age in iLGG was 37.9 years (p = 0.004). There was significant difference in mean blood loss between cLGG and iLGG groups (270 and 411 ml respectively, p = 0.020). cLGG had a significantly higher proportion of grade II tumors (p < 0.001). The overall mean survival time for the iLGG group was 14.96 +/- 1.23 months, and 18.77 +/- 2.72 months for the cLGG group. In univariate cox regression, the survival difference between LGG groups was not significant (HR = 0.888, p = 0.581), however on multivariate regression cLGG showed a significant (aHZ = 0.443, p = 0.015) positive correlation with survival. Intense contrast enhancement (HZ = 41.468, p = 0.018), blood loss (HZ = 1.002, p = 0.049), and moderately high Ki-67 (HZ = 4.589, p = 0.032) were also significant on univariate analyses. Conclusion: cLGG and iLGG are radiologically distinct groups with separate prognoses, surgical experience, and associations.