Impact of 1p/19q codeletion status on extent of resection in WHO grade II glioma: Insights from a national cancer registry

Objective: Traditionally, extent of resection (EOR) has been seen as a surgical parameter that can predict survival outcomes of surgically managed WHO grade II gliomas. The aim of this study was to evaluate if such an influence was potentially affected by 1p/19q codeletion status based on a national cancer registry. Patient and methods: All adults diagnosed with grade II gliomas between the years 2004 to 2014 were queried from the National Cancer Database (NCDB). The population was then divided based on 1p/19q codeletion status, and then Kaplan-Meier, univariate and multivariate Cox regression analyses were utilized to evaluate the prognostic effect of EOR. Results: In total, 1,498 grade II gliomas satisfied inclusion for analysis, with the 1p/19q non-codeleted in 705 (47%) cases, and codeletion in 793 (53%) cases. When the cohort was divided based on codeletion status, Kaplan-Meier modelling and univariate regression analyses indicated that gross total resection (GTR) was significantly associated with greater 5-overall survival (OS) in both 1p/19q non-codeleted and codeletion groups. Upon multivariate analysis which incorporated adjuvant therapy status, the significance of GTR was only retained in the 1p/19q non-codeletion group after post-hoc adjustment. Conclusion: Our findings indicate that the survival impact of GTR in grade II gliomas may be affected by 1p/19q codeletion status within the first five years after surgery based on overall survival. Therefore, molecular diagnostics have potential clinical application in surgery outcomes, and validation of the reported findings will assist in surgical planning if such an association can be thoroughly established.