Purpose: To evaluate the hypothesis that adults with partially resected (PR<50% resection) supratentorial low-grade glioma (LGG) benefit from higher doses of radiation.
Methods: Patients receiving post-operative radiation for WHO grade I-II LGG at the University of Western Ontario between 1979 and 2001 were studied. Patient characteristics evaluated included: age, gender, symptom duration>30 days, seizures at presentation, Karnofsky performance status (KPS)<70, astrocytoma pathology (AS), and radiation dose. A Cox proportional hazard regression model was constructed to test the influence of radiation dose.
Results: One hundred and seven patients were analyzed. Patients who had PR were not significantly different from those with STR (subtotal/total resection) in terms of patient characteristics. Median survival (MST) of PR patients who received<or=50 Gy was 16.5 months while those who received>50 Gy had a MST of 109.2 months. The interaction of radiation dose and extent of resection was tested after controlling for other patient factors by Cox regression model. The interaction was highly significant for both OS and PFS (P=0.013 and P=0.003, respectively). This model remained significant after excluding six patients receiving doses<42 Gy (OS, P=0.024, and PFS, P=0.001).
Conclusions: The outcome for patients with LGG is dependent on extent of tumor resection and radiation dose. Patients with PR should be considered for higher radiation dose schedules (>50 Gy). Future trials on therapeutic strategies for LGG should consider stratification of patients by extent of tumor resection. Our data suggests that one dose does not fit all.