Radiotherapy in adult low-grade glioma: nationwide trends in treatment and outcomes

Background: Management of WHO grade II gliomas (LGG) can include a combination of observation, surgery, radiotherapy (RT), and chemotherapy; however, optimal management remains unclear in regards to RT. Objective: The current study seeks to investigate the usage of RT in LGG and its effect on survival outcomes. Methods: Patients with diagnosis codes specific for LGG were queried from the National Cancer Database (NCDB) during the years 2004–2016. Kaplan–Meier curves with log-rank testing, univariate and multivariate Cox regression analysis, and comparisons of estimated 3- and 7-year survival were performed to investigate the effect of RT on overall survival. Results: 19,382 patients with LGG were identified with histologically confirmed disease. Kaplan–Meier testing demonstrated RT impacted survival in patients undergoing biopsy or no surgery (p < 0.0001), no chemotherapy (p < 0.0001), and in regimens with early RT (p < 0.0001) and high-dose RT (p < 0.0001). Cox multivariate regression demonstrated RT and age less than 40 (HR 0.93, 95% CI 0.89–0.97, p = 0.001), no chemotherapy (HR 0.82, 95% CI 0.77–0.87, p < 0.001), and astrocytoma histology (HR 0.72, 95% CI 0.66–0.79, p < 0.001) were associated with improved survival. 3-year survival of RT versus non-RT groups showed increased survival rates for age less than 40 years (+ 5.7%, p < 0.0001), no surgery or biopsy (+ 8.1%, p < 0.0001), no chemotherapy (+ 10.3%, p < 0.0001), mixed glioma (+ 6.7%, p < 0.0001), astrocytoma (+ 7.1%, p < 0.0001), and in regimens with early RT (+ 7.6%, p < 0.0001) and high-dose RT (+ 4.7%, p < 0.0001). Conclusion: This nationwide analysis of LGG patients found that RT was associated with improved survival outcomes in patients less than 40 years of age, with histology subtypes of astrocytoma and mixed glioma, undergoing biopsy or no surgery, and in regimens with early RT and high-dose RT.