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MO_5_2584 - Defining an Intermediate Risk Group for Low Grade Glioma. An Analysis of the National Cancer Database

Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3

Defining an Intermediate Risk Group for Low Grade Glioma? An Analysis of the National Cancer Database
V. Jairam1, B. H. Kann2, H. S. M. Park2, J. A. Miccio2, J. M. Beckta3, J. B. Yu2, S. Gao3, R. S. Prabhu4, M. P. Mehta5, W. J. Curran Jr6, R. S. Bindra2, J. N. Contessa2, and K. Patel2; 1Yale School of Medicine, New Haven, CT, 2Department of Therapeutic Radiology, Yale School of Medicine, New Haven, CT, 3Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT, 4Southeast Radiation Oncology Group, Levine Cancer Institute, Carolinas HealthCare System, Charlotte, NC, 5Miami Cancer Institute, Baptist Health South Florida, Miami, FL, 6Department of Radiation Oncology, Winship Cancer Institute of Emory University, Atlanta, GA

Purpose/Objective(s): Low-risk low-grade gliomas (LR-LGG) were defined by RTOG 9802 based on age younger than 40 years and gross total resection (GTR). However, analyses of EORTC studies in LGG patients have uncovered other prognostic factors, including size, histology, and molecular biomarkers. While observation after GTR was established as the standard of care for LR-LGG, a number of these patients still receive adjuvant therapy. The aim of this study is to investigate characteristics associated with receipt of adjuvant therapy and with overall survival (OS) for patients with LR-LGG.

Materials/Methods: The National Cancer Data Base was used to identify patients with histologically confirmed LR-LGG diagnosed between 2010 to 2013. All patients were between ages 18 to 39 years and had a GTR. Demographic and clinicopathologic predictors of observation vs. adjuvant therapy (chemotherapy and/or radiotherapy) were analyzed using the chi-squared, ANOVA tests, and logistic regression analysis. OS was estimated using the Kaplan-Meier analysis log-rank tests; Cox proportional hazards regression models, multivariable logistic regression analyses, and 1:1 propensity score matching were also utilized.

Results: 1046 patients with LR-LGG were identified: 838 (80.1%) underwent observation and 208 (19.9%) received adjuvant therapy within 6 months of surgery. The median follow-up was 3.9 years, while the median tumor size was 4 cm. Histologic breakdown was 42% astrocytoma, 33% oligodendroglioma, and 25% mixed glioma. Patients receiving adjuvant treatment were more likely (all p<0.05) to have non-oligodendroglioma histology (72.6 vs. 65.2%), tumor size > 5 cm (32.2 vs. 19.9%), or a multifocal tumor (6.0 vs. 1.5%). On logistic regression, older age, multifocality, and tumor size > 5 cm predicted for receipt of adjuvant therapy. On Cox regression, tumor size > 5 cm (hazard ratio [HR]: 2.23; 95% confidence interval [CI], 1.20 – 4.31) and non-oligodendroglioma histology (HR: 2.74; 95% CI, 1.48 – 5.11) were associated with worse OS (all p<0.05). For patients with tumors > 5 cm and non-oligodendroglioma histology (a subset we consider “intermediate-risk”), 5-year OS was 77.8%, compared to 94.2% for those with smaller oligodendroglial tumors (p<0.001). After propensity score matching, the intermediate-risk group continued to be associated with worse OS (80.0 vs. 92.7%, p=0.048).

Conclusion: In spite of being labeled “low-risk”, 20% of these patients received adjuvant therapy. We propose an “intermediate-risk” classification for patients with > 5 cm non-oligodendroglioma tumors due to inferior survival. Prospective studies incorporating molecular markers and investigating the benefit of adjuvant therapy are warranted for this subgroup.

Author Disclosure: V. Jairam: None. H.S. Park: Employee; Yale School of Medicine. J.A. Miccio: None. J.B. Yu: Research Grant; 21st Century Oncology. Consultant; Augmenix. S. Gao: None. M.P. Mehta: Consultant; Varian, Oncoceutics, Astra-Zeneca, Celgene, Tocagen, Abbvie. monitor data safety; Monteris. Board of Directors; Oncoceutics. W.J. Curran: Board Member; ASCO. R.S. Bindra: Stock Options; Cybrexa Therapeutics. J.N. Contessa: None. K. Patel: None.

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