Single-Institution Experience Of Low-Grade Glioma Patient Outcomes Eligible For Rtog 9802

Long-term results of RTOG 9802 demonstrate a survival benefit for adjuvant (adj) chemotherapy (CT) vs radiotherapy (RT) alone in high-risk low grade glioma (LGG). While this study matured, clinical practice patterns continued to include observation following resection for these same patients. It is unknown if RT + CT yields a survival benefit compared to observation. As such, we compared outcomes of patients with high risk LGG, eligible for adj therapy on RTOG 9802 (age ≥ 40 years regardless of extent of resection, or age < 40 years with less than a gross total resection [GTR]), treated at a single institution during this era. Records from adults diagnosed with LGG between 1997 and 2008 were assessed. Patients were at least 18 years of age with a WHO grade II glioma confirmed by pathology review at our institution. Univariate and multivariate analysis (MVA) of prognostic factors were performed using JMP statistical software. Kaplan-Meier estimates were used to determine progression-free survival (PFS) and overall survival (OS) and compared using Log-rank test. Tumor registry search returned 554 adults with LGG, of whom 276 met criteria for this analysis. The median age of all patients was 42 years; 157 patients ≥ 40 years at diagnosis and 119 patients <40 years with less than a GTR. The median follow-up was 6.2 years (0.1-18.1). Fifty-eight (21%), 101 (37%) and 117 (42%) patients had histology of astrocytoma (A), oligoastrocytoma (OA) and oligodendroglioma (O), respectively. Surgical resection was biopsy-only, subtotal resection (STR) and GTR in 135 (49%), 107 (39%), and 34 (12%) patients, respectively. Adj therapy, included observation in 81 (29%) patients, RT alone in 129 (47%) patients, RT + CT in 56 (20%) patients, and CT alone 10 (4%) patients. CT included: n = 37 (57%) temozolomide, n = 25 (38%) PCV, n = 3 (5%) other. Median PFS was 3.5 years (2.9, 3.5 and 4.7 years for A, OA, and O, respectively, P = 0.0008). Median PFS by adj therapy was 2.8, 4.1, 5.0, and 5.3 years for observation, RT alone, CT alone, and RT + CT, respectively, P = 0.02). Median OS was 9.3 years (5.1, 8.8, and 14.1 years for A, OA, and O, respectively, P < 0.0001). Median OS by adj therapy was of 11.8, 8.1, 14.2, and 14.0 years for observation, RT alone, CT alone, and RT + CT, respectively, (P = 0.08). MVA using histology, extent of resection, and adj therapy, demonstrated RT + CT was associated with an improved OS compared to RT alone (HR = 0.59; 95% CI = 0.37-0.91; P = 0.02) but not compared to observation (HR = 0.63; 95% CI = 0.35-1.13; P = 0.13). Observed patients were more likely to be O or OA histology or have a GTR (P = 0.05 and P < 0.001, respectively). Our study shows similar patient characteristics and confirms outcomes to those patients enrolled on RTOG 9802. Adj RT + CT was associated with improved OS vs RT alone. RT + CT was not was not associated with statistically significant improvement in OS compared to initial observation. Observation may be a reasonable approach after resection for appropriately selected LGG.