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Abstract BACKGROUND Radiation Therapy Oncology Group 9802 was a phase III trial for patients with centrally confirmed LGG (WHO grade II). Participants ³ 40 years or those with neurosurgeon defined less than gross total resection (GTR) were randomized to radiotherapy (RT) +/- PCV. In a separate cohort, adults age < 40 years with neurosurgeon defined GTR were observed by MRI every 6 months without adjuvant therapy. At last report, outcome for the observation cohort was immature with median follow-up of only 4.4 years. Here, we present mature outcomes for the observation arm. METHODS Eligible adults (as above) were observed by MRI every 6 months. OS and PFS were estimated by Kaplan-Meier method and estimated hazard ratios to characterize the prognostic variables. RESULTS There were 111 eligible patients (median age 30; median KPS = 100). Median follow-up was 16.1 years with 71 (64%) alive at the last follow-up. 79 patients (71%) had progressed with median PFS of 6.9 years. 5, 10, and 15 year-PFS and OS rates were 54%, 39%, 28% and 94%, 77%, and 65%. 1p19q status was codeleted in 32%, IDH1/2 mutant in 78% and MGMT promoter methylated in 39% of tested cases. Multivariate Cox analyses showed that preoperative tumor size ³ 4 cm (HR = 2.43 for PFS, p = 0.001; HR = 2.58 for death, p = 0.016) and residual disease on imaging ³ 1 cm (HR = 2.97 for PFS, P < 0.001; HR = 2.02 for death, p = 0.05) were associated with worse outcomes. Analyses based on molecular results will be presented. CONCLUSION A subset of low-grade gliomas can be observed after the initial resection based on younger age, smaller tumor size, and no residual disease on neuroimaging. This can likely be further refined by prognostic molecular markers. Patients with the most favorable prognostic factors can avoid or delay the acute and long-term side effects of RT and chemotherapy for several years.

PURPOSENRG Oncology/RTOG 9802 (ClinicalTrials.gov Identifier: NCT00003375 ) is a practice-changing study for patients with WHO low-grade glioma (LGG, grade II), as it was the first to demonstrate a survival benefit of adjuvant chemoradiotherapy over radiotherapy. This post hoc study sought to determine the prognostic and predictive impact of the WHO-defined molecular subgroups and corresponding molecular alterations within NRG Oncology/RTOG 9802.METHODSIDH1/2 mutations were determined by immunohistochemistry and/or deep sequencing. A custom Ion AmpliSeq panel was used for mutation analysis. 1p/19q codeletion and MGMT promoter methylation were determined by copy-number arrays and/or Illumina 450K array, respectively. Progression-free survival (PFS) and overall survival (OS) were estimated using the Kaplan-Meier method. Hazard ratios (HRs) were calculated using the Cox proportional hazard model and tested using the log-rank test. Multivariable analyses (MVAs) were performed incorporating treatment and common prognostic factors as covariates.RESULTSOf the eligible patients successfully profiled for the WHO-defined molecular groups (n = 106/251), 26 (24%) were IDH-wild type, 43 (41%) were IDH-mutant/non-codeleted, and 37(35%) were IDH-mutant/codeleted. MVAs demonstrated that WHO subgroup was a significant predictor of PFS after adjustment for clinical variables and treatment. Notably, treatment with postradiation chemotherapy (PCV; procarbazine, lomustine (CCNU), and vincristine) was associated with longer PFS (HR, 0.32; P = .003; HR, 0.13; P < .001) and OS (HR, 0.38; P = .013; HR, 0.21; P = .029) in the IDH-mutant/non-codeleted and IDH-mutant/codeleted subgroups, respectively. In contrast, no significant difference in either PFS or OS was observed with the addition of PCV in the IDH-wild-type subgroup.CONCLUSIONThis study is the first to report the predictive value of the WHO-defined diagnostic classification in a set of uniformly treated patients with LGG in a clinical trial. Importantly, this post hoc analysis supports the notion that patients with IDH-mutant high-risk LGG regardless of codeletion status receive benefit from the addition of PCV.

1500 Background: Treatment of adult LGG is controversial. Favorable patients (pts) (age <40 years [yrs] who undergo gross total resection [GTR]) are typically observed. Unfavorable pts (age ≥40 who have subtotal resection [STR] or biopsy [B]) are usually given initial radiation therapy (RT), reserving chemotherapy (historically procarbazine, CCNU and vincristine [PCV]) for recurrence. In 1998, the RTOG, in conjunction with SWOG, NCCTG, and ECOG initiated prospective studies of adult LGG, the results of which are reported herein. Methods: Favorable pts were observed postoperatively in a single arm Phase II study (Arm 1). Unfavorable pts were stratified by age, histology, KPS, and presence/absence of contrast enhancement on preoperative magnetic resonance imaging and randomized to either RT alone (54Gy in 30 fractions to a local treatment field) (Arm 2) or RT followed by 6 cycles of standard dose PCV (Arm 3). Reported results include overall survival (OS) rate, median overall survival time (MOST), progression-free survival (PFS) rate, and median progression-free survival time (MPFST). Survival data are compared using Wilcoxon p-values. Results: A total of 362 eligible/analyzable pts were accrued between 1998 and 2002. Median follow-up time is 4 years. For the 111 favorable pts observed on Arm 1, OS at 2- and 5-yrs is 99% and 94%. PFS at 2- and 5-yrs is 82% and 50%. For the 251 unfavorable pts on Arms 2 (RT alone) and 3 (RT+PCV), there was no difference in OS or PFS. OS at 2- and 5-yrs was 87% and 61% with RT alone versus (vs) 86% and 70% with RT+PCV (p=0.72). MOST was not reached in RT alone pts and was 6.0 yrs in RT+PCV pts. PFS at 2- and 5-yrs was 73% and 39% with RT alone vs 72% and 61% with RT+PCV (p=0.38). MPFST was 4.0 yrs with RT alone vs 6.0 yrs with RT+PCV. Acute grade 3–4 toxicity occurred in 9% of pts who received RT alone, 67% who received RT+PCV (mostly hematologic). There were no treatment deaths on either arm. Conclusions: 5-yr PFS was poor in all three arms ranging from 39% to 61%. Only half of favorable pts were disease-free at 5 yrs. In unfavorable pts, there was no OS advantage with the addition of PCV to RT. Both PFS and MPFST were better with the addition of PCV, but not significantly. Analysis of outcome by 1p19q status is pending. No significant financial relationships to disclose.

Purpose The addition of PCV (procarbazine, lomustine, and vincristine) chemotherapy to radiotherapy (RT) for patients with WHO grade 2 glioma improves progression-free survival (PFS). The effect of therapy intensification on cognitive function (CF) remains a concern in this population with substantial long-term survival. Patients and Methods A total of 251 patients with WHO grade 2 glioma age ≥ 40 years with any extent of resection or age < 40 years with subtotal resection/biopsy were randomly assigned to RT (54 Gy) or RT plus PCV. We observed 111 patients age < 40 years with gross total resection. CF was assessed by Mini–Mental State Examination (MMSE) at baseline and years 1, 2, 3, and 5. Results Overall, few patients experienced significant decline in MMSE score. There were no significant differences in the proportion of patients experiencing MMSE score decline between the randomized study arms at any time point. Both study arms experienced a significant gain in average MMSE score longitudinally over time, with no difference between arms. Conclusion The MMSE is a relatively insensitive tool, and subtle changes in CF may have been missed. However, the addition of PCV to RT did not result in significantly higher rates of MMSE score decline than RT alone through 5 years of follow-up. Patients in both randomly assigned arms experienced a statistically significant average MMSE score increase over time, with no difference between arms. The addition of PCV chemotherapy to RT improves PFS without excessive CF detriment over RT alone for patients with low-grade glioma.

Purpose A prior Radiation Therapy Oncology Group (RTOG) clinical trial in anaplastic oligodendroglioma suggested a progression-free survival benefit for procarbazine, lomustine, and vincristine (PCV) chemotherapy in addition to radiation therapy (RT), as have smaller trials in low-grade glioma (LGG). Patients and Methods Eligibility criteria included supratentorial WHO grade 2 LGG, age 18 to 39 years with subtotal resection/biopsy, or age ≥ 40 years with any extent resection. Patients were randomly assigned to RT alone or RT followed by six cycles of PCV. Survival was compared by using the modified Wilcoxon and log-rank tests. Results In all, 251 patients were accrued from 1998 to 2002. Median overall survival (OS) time and 5-year OS rates for RT versus RT + PCV were 7.5 years versus not reached and 63% versus 72%, respectively (hazard ratio [HR]; 0.72; 95% CI, 0.47 to 1.10; P = .33; log-rank P = .13). Median progression-free survival (PFS) time and 5-year PFS rates for RT versus RT + PCV were 4.4 years versus not reached and 46% versus 63%, respectively (HR, 0.6; 95% CI, 0.41 to 0.86; P = .06; log-rank P = .005). OS and PFS were similar for all patients between years 0 and 2. After 2 years, OS and PFS curves separated significantly, favoring RT + PCV. For 2-year survivors (n = 211), the probability of OS for an additional 5 years was 74% with RT + PCV versus 59% with RT alone (HR, 0.52; 95% CI, 0.30 to 0.90; log-rank P = .02). Conclusion PFS but not OS was improved for adult patients with LGG receiving RT + PCV versus RT alone. On post hoc analysis, for 2-year survivors, the addition of PCV to RT conferred a survival advantage, suggesting a delayed benefit for chemotherapy.

Object In 1998, the Radiation Therapy Oncology Group initiated a Phase II study of observation for adults < 40 years old with cerebral low-grade glioma who underwent a neurosurgeon-determined gross-total resection (GTR). Methods Patient eligibility criteria included the presence of a World Health Organization Grade II astrocytoma, oligodendroglioma, or mixed oligoastrocytoma confirmed histologically; age 18–39 years; Karnofsky Performance Scale score ≥ 60; Neurologic Function Scale score ≤ 3; supratentorial tumor location; neurosurgeon-determined GTR; and pre- and postoperative MR imaging with contrast enhancement available for central review by the principal investigator. Patients were observed following GTR and underwent MR imaging every 6 months. Prognostic factors analyzed for their contribution to patient overall survival, progression-free survival (PFS), and tumor recurrence included age, sex, Karnofsky Performance Scale score, Neurologic Function Scale score, histological type, contrast enhancement on preoperative MR imaging, preoperative tumor diameter, residual disease based on postoperative MR imaging, and baseline Mini-Mental State Examination score. Results Between 1998 and 2002, 111 eligible patients were entered into the study. In these 111 patients, the overall survival rates at 2 and 5 years were 99 and 93%, respectively. The PFS rates in these 111 patients at 2 and 5 years were 82 and 48%, respectively. Three prognostic factors predicted significantly poorer PFS in univariate and multivariate analyses: 1) preoperative tumor diameter ≥ 4 cm; 2) astrocytoma/oligoastrocytoma histological type; and 3) residual tumor ≥ 1 cm according to MR imaging. Review of the postoperative MR imaging results revealed that 59% of patients had < 1 cm residual disease (with a subsequent 26% recurrence rate), 32% had 1–2 cm residual disease (with a subsequent 68% recurrence rate), and 9% had > 2 cm residual disease (with a subsequent 89% recurrence rate). Conclusions These data suggest that young adult patients with low-grade glioma who undergo a neurosurgeondetermined GTR have a > 50% risk of tumor progression 5-years postoperatively, warranting close follow-up and consideration for adjuvant treatment.