Supratentorial low-grade glioma: Results and prognostic factors following postoperative radiotherapy

Background and Purpose: To assess treatment outcome and prognostic factors following postoperative external radiotherapy in 77 patients with low-grade glioma. Patients and Methods: Between 1977 and 1996, 45 patients with astrocytoma, 14 with oligodendroglioma and 18 with mixed glioma received postoperative r adiotherapy with a median total dose of 52 Gy (range, 45 to 61 Gy). Sixty-s even patients were treated immediately following surgery, 10 patients with tumor progression. The influence of various factors including histology, ge nder, age, seizures, duration of symptoms (less than or equal to 6 weeks vs > 6 weeks), CT pattern (enhancement vs no enhancement), type of surgery, t otal radiotherapy dose and timing of radiotherapy on relapse-free survival and overall survival was investigated. Results: The median overall survival time was 81 months, the 5- and 10-year survival rates were 54% and 31%, respectively. The median time to progress ion was 56 months, while the 5- and 10-year progression-free survival rates were 45% and 24%. Univariate analyses identified the total radiotherapy do se (p = 0.01), duration of symptoms (p = 0.05), the presence of seizures (p = 0.04), and the CT pattern following intravenous contrast (p = 0.005) as significant prognostic factors for overall survival. Progression-free survi val rates were influenced by the total dose (p = 0.04), the duration of sym ptoms (p = 0.01) and CT pattern (p = 0.006). On multivariate analysis, only the CT pattern (enhancement vs no enhancement) remained as independent pro gnostic factors for both progression-free survival and overall survival. Conclusion: A minimum total dose of 52 Gy is recommended for the postoperat ive radiotherapy in low-grade glioma. Tumors with CT enhancement seem to ne ed further intensification of treatment.