Low grade glioma radiotherapy
Postoperative policies of “wait-and-see” and radiotherapy for low grade glioma are poorly defined. A trial in the mid 1980s established the radiation dose. In 1986 the EORTCRadiotherapy and Brain Tumor Groups initiated a prospective trial to compare early radiotherapy with delayed radiotherapy.
After surgery, patients from 24 centres across Europe were randomly assigned to either early radiotherapy of 54 Gy in fractions of 1.8 Gy or deferred radiotherapy until the time to progression (control group). Patients with low-grade astrocytoma, oligodendroglioma, mixed oligoastrocytoma, and incompletely resected pilocytic astrocytoma, with a WHO performance status 0-2 were eligible. Analysis was by intention to treat, and primary endpoints were overall and progression-free survival.
157 patients were assigned early radiotherapy, and 157 control. Median progression-free survival was 5.3 years in the early radiotherapy group and 3.4 years in the control group (hazard ratio 0.59, 95% CI 0.45-0.77; p<0.0001). However, overall survival was similar between groups: median survival in the radiotherapy group was 7.4 years compared with 7.2 years in the control group (hazard ratio 0.97, 95% CI 0.71-1.34; p=0.872). In the control group, 65% of patients received radiotherapy at progression. At 1 year, seizures were better controlled in the early radiotherapy group.
Early radiotherapy after surgery lengthens the period without progression but does not affect overall survival. Because quality of life was not studied, it is not known whether time to progression reflects clinical deterioration. Radiotherapy could be deferred for patients with low-grade glioma who are in a good condition, provided they are carefully monitored 1).
Early radiotherapy (RT) (54 Gy in fractions of 1.8 Gy) is recommended as adjuvant therapy and is shown to prolong median progression free survival (PFS) from 3.4 to 5.3 years but does not affect overall survival 2).
In patients with the tumor radically resected, early RT did not prolong PFS and is recommended to be deferred until progression. Following incomplete resection, early RT significantly prolongs PFS and disease specific survival 3).
Two prospective trials found no difference in OS or PFS between different XRT doses (EORTC trial 4): 45 Gy in 5 weeks vs. 59.4 Gy in 6.6 weeks; Intergroup study 5) 50.4 vs. 64.8 Gy).
In a cohort of patients with low grade glioma who were younger than 40 years of age and had undergone subtotal resection or who were 40 years of age or older, progression free survival and overall survival were longer among those who received combination chemotherapy in addition to radiation therapy than among those who received radiation therapy alone. (Funded by the National Cancer Institute and others; ClinicalTrials.gov number, NCT00003375.) 6).
There was no significant difference in progression free survival in patients with low grade glioma when treated with either radiotherapy alone or temozolomide chemotherapy alone. Further data maturation is needed for overall survival analyses and evaluation of the full predictive effects of different molecular subtypes for future individualised treatment choices 7).
The effect of temozolomide chemotherapy or radiotherapy on HRQOL or global cognitive functioning did not differ in patients with low-grade glioma. These results do not support the choice of temozolomide alone over radiotherapy alone in patients with high-risk low-grade glioma 8).
Early radiation therapy was associated with the following adverse effects: skin reactions, otitis media, mild headache, nausea, and vomiting. People with LGG who undergo early radiotherapy showed an increase in time to progression compared with people who were observed and had radiotherapy at the time of progression. There was no significant difference in overall survival between people who had early versus delayed radiotherapy; however, this finding may be due to the effectiveness of rescue therapy with radiation in the control arm. People who underwent early radiation had better seizure control at one year than people who underwent delayed radiation. There were no cases of radiation-induced malignant transformation of LGG. However, it remains unclear whether there are differences in memory, executive function, cognitive function, or quality of life between the two groups since these measures were not evaluated 9).
Twenty adult patients with supratentorial low-grade glioma were treated with 50.4 Gy (10 patients) or 64.8 Gy (10 patients) localized RT. The patients then were evaluated with an extensive battery of psychometric tests at baseline (before RT) and at approximately 18-month intervals for as long as 5 years after completing RT. To allow patients to serve as their own controls, cognitive performance was evaluated as change in scores over time. All patients underwent at least two evaluations.
Baseline test scores were below average compared with age-specific norms. At the second evaluation, the groups’ mean test scores were higher than their initial performances on all psychometric measures, although the improvement was not statistically significant. No changes in cognitive performance were seen during the evaluation period when test scores were analyzed by age, treatment, tumor location, tumor type, or extent of resection.
Cognitive function was stable after RT in these patients evaluated prospectively during 3 years of follow-up. Slight improvements in some cognitive areas are consistent with practice effects attributable to increased familiarity with test procedures and content 10).
A phase III prospective randomized trial of low- versus high-dose radiation therapy for adults with supratentorial low-grade astrocytoma, oligodendroglioma, and oligoastrocytoma found somewhat lower survival and slightly higher incidence of radiation necrosis in the high-dose RT arm. The most important prognostic factors for survival are histologic subtype, tumor size, and age 11).