Object: To determine principal prognostic factors and the effect of timing of radiotherapy (RT) on disease-specific survival (DSS) and progression-free survival (PFS) in WHO Grade II astrocytomas.
Methods: Histologic slides of 166 consecutive patients with the original tissue diagnosis of low-grade, non-pilocytic astrocytoma were reviewed. One-hundred and six were selected where two additional certified neuropathologist agreed on the grading of WHO Grade II astrocytoma. In 97 out of 106 cases follow-up informations were available. Early postoperative RT was given to 36 out of 97 patients (37%). The two groups of patients (early vs. delayed RT) were well balanced in respect to extent of surgery and other main clinical prognostic factors. Median follow-up of surviving patients was 79 months. The 5- and 10-year PFS was 52.2% and 30.7% with early RT and 39.5% and 12.4% with delayed RT (p = 0.0388). In respect to DSS, there was no significant difference in the 5- and 10-year actuarial survival rate according to the timing of RT (60.5% and 26.5% vs. 66.6% and 23.7%; p = 0.7545). Age (p = 0.0145) and extent of surgery (p = 0.0473) were significant prognostic variables in respect to DSS. Subdividing the irradiated group based on the extent of surgery, early RT in the subtotal group significantly improved 5-year PFS (60.0% vs. 12.4%; p = 0.0036) and DSS (66.7% vs. 49.8%; p = 0.0389). However, postoperative RT had no influence on PFS (p = 0.6812) and DSS (p = 0.3987) in the group with extensive resection.
Conclusion: Early postoperative RT in subtotally resected, Grade II astrocytomas significantly improves both progression-free and disease-specific survival. Early RT does not benefit patients with extensive resection, RT should be withheld in these patients until progression.