OBJECTIVE RTOG 9802 demonstrated improved survival using chemoradiotherapy (CRT) over radiotherapy (RT) alone for WHO Grade II gliomas (LGG) using PCV with RT. We analyze our retrospective dataset of predominantly temozolomide (TMZ)-based CRT in LGG patients who would have been eligible for RTOG 9802. METHODS Retrospective review of LGG patients (2000–2017) treated at a single institution (67 patients). Histologies included oligodendroglioma(OD), astrocytoma(AC) or astrocytoma (OA). Those who received upfront RT +/- chemotherapy were included. The CRT cohort (n=40) consisted primarily of TMZ (n=36) administered concurrently with RT. 27 patients received RT alone. RT for both cohorts consisted of a median dose of 54 Gy (range 50.4 - 54 Gy). 65/67 patients had “high risk” LGG as defined by RTOG 9802 criteria. Kaplan Meier analysis was used to assess overall survival (OS) and progression free survival (PFS). RESULTS 5-year PFS for patients receiving CRT was 64% vs. 44% in those receiving RT alone (log rank p=0.009). Difference in PFS due to chemotherapy was driven by AC histology (57% vs. 21% PFS at 5 years, log rank p=0.002) while OD/OA PFS was not statistically altered (79% vs. 72% PFS at 5 years, p=0.21). 5-year OS for patients receiving CRT was 76% vs. 69% in those receiving RT alone (p=0.11). Cox Proportional Hazards analysis showed that use of upfront CRT (HR=0.4, p=0.009) was the only factor that decreased the risk of earlier progression. CONCLUSION Use of upfront, predominantly TMZ-based CRT, has a PFS benefit over RT alone in a population of WHO grade II gliomas. This benefit appears to be driven by AC histology and also appears to extend beyond the “very high risk” cohort from RTOG 0424 to include the “high risk” group from RTOG 9802.

Purpose: RTOG 9802 demonstrated improved survival with the use of chemoradiotherapy (CRT) over radiotherapy (RT) alone for WHO grade II gliomas (LGG) using PCV chemotherapy. We analyzed our retrospective dataset of predominantly temozolomide (TMZ)-based CRT in patients with LGG who would have been eligible for RTOG 9802. Methods: We identified 67 patients (n= 38 astrocytoma (AC), 20 oligodendroglioma (OD), and 9 mixed (OA)) treated with upfront RT from 2000-2017. The CRT cohort (n=40) primarily consisted of TMZ (n=36) administered concurrently with RT. The median RT dose was 54 Gy (range 35-54 Gy). Kaplan- Meier analysis was used to assess overall survival (OS) and progression-free survival (PFS). Results: 5-year PFS was 64% vs. 44% for patients receiving CRT vs. RT alone (log-rank p=0.009). 5-year PFS for AC patients receiving CRT vs. RT alone was 57% vs. 21%, respectively (log-rank p=0.002) while 5-year PFS for OD/OA patients receiving CRT vs. RT alone was 79% vs. 72% (p=0.21). 5-year OS was 76% vs. 69% (p=0.10 ) for CRT vs. RT alone. Cox Proportional Hazards analysis revealed that patients with AC (HR=4.89, 95% CI (1.95, 12.3), p=0.0007), neurological deficits (HR=2.34, (1.12, 4.88), p=0.023), and tumors>6 cm (HR=2.69, (1.10, 6.58), p=0.03) had decreased OS. Cox analysis showed that use of upfront CRT (HR=0.40 , (0.20, 0.79), p=0.0086) was the only factor that improved PFS. Conclusion: The use of upfront, predominantly TMZ-based, CRT has a PFS benefit over RT alone in patients with LGG.

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