Comprehensive evaluation of treatment and outcomes of low-grade diffuse gliomas.

Background: Low-grade gliomas affect younger adults and carry a favorable prognosis. They include a variety of biological features affecting clinical behavior and treatment. Having no guidelines on treatment established, we aim to describe clinical and treatment patterns of low-grade gliomas across the largest cancer database in the United States.

Methods: We analyzed the National Cancer Database from 2004 to 2015, for adult patients with a diagnosis of World Health Organization grade II diffuse glioma.

Results: We analyzed 13,621 cases with median age of 41 years. Over 56% were male, 88.4% were white, 6.1% were black, and 7.6% Hispanic. The most common primary site location was the cerebrum (79.9%). Overall, 72.2% received surgery, 36.0% radiation, and 27.3% chemotherapy. Treatment combinations included surgery only (41.5%), chemotherapy + surgery (6.6%), chemotherapy only (3.1%), radiation + chemotherapy + surgery (10.7%), radiation + surgery (11.5%), radiation only (6.1%), and radiotherapy + chemotherapy (6.7%). Radiation was more common in treatment of elderly patients, 1p/19q co-deletion (37.3% versus 24.3%, p<0.01), and tumors with midline location. Median survival was 11 years with younger age, 1p/19q co-deletion, and cerebrum location offered survival advantage.

Conclusions: Tumor location, 1p/19q co-deletion, and age were the main determinants of treatment received and survival, likely reflecting tumor biology differences. Any form of treatment was preferred over watchful waiting in the majority of the patients (86.1% versus 8.1%). Survival of low-grade gliomas is higher than previously reported in the majority of clinical trials and population-based analyses. Our analysis provides a real world estimation of treatment decisions, use of molecular data, and outcomes.