Low Grade Astrocytoma-Need Postoperative Radiotherapy or Not?

Hong, Seong Eon; Choi, Doo Ho; Kim, Tae Sung; Leem, Won

Abstract

The precise role of radiotherapy for low grade gliomas including the optimal radiation dose and timing of treatment remains unclear. The information given by a retrosepctive analysis may be useful in the design of prospective randomized studies looking at radiation dose and time of surgical and radiotherapeutic treatment. The records of 56 patients (M:F=29:27) with histologically verified cerebral low grade gliomas(47 cases of grade 1 or 2 astrocytomas and 9 oligodendrogliomas) diagnosed between 1979 and 1989 were retrospectively reviewed. The extent of surgical tumor removal was gross total or radical subtotal in 38 patients(68%) and partial or biopsy only in the remaining 18 patients(32%). Postooperative radiation therapy was given to 36 patients(64%) of the total 56 patients with minimum dose of 5000 cGy (range=1250 to 7220 cGy). The 5-and 10-year survival rates for the total 56 patients were 44% and 32% respectively with a median survival of 4.1 years. According to the histologic grade the 5- and 10-year survivals were 52% and 35% for the 24 patients respectively with grade I astrocytomas compared to 20% and 10% for the 23 patients with grade II astrocytomas. Survival of oligodendroglioma patients was greater than those with astrocytoma (65% vs 36% at 5 years), and the difference was also remarkable in the long term period of follow up (54% vs 23% at 10 years). Those who received high-dose radiation therapy (> or =5400 cGy) had significant better survival than those who received low-dose radiation(< 5400 cGy) or surgery alone (p<0.05). The 5-and 10-year survival rates were, respectively 59% and 46% for the 23 patients receiving high-dose radiation, 36% and 24% for the 13 patients receiving low-dose radiation, and 35% and 26% for the 20 patients with surgery alone. Survival rates by the extent of surgical resection were similar at 5 years (46% vs 41%), but long term survival was quite different (p<0.01) between total/subtotal resection and partial esection/biopsy (41% and 12%, resepctively). Previously published studies have identified important prognostic factors in these tumor : age, extent of surgery, grade, performance status, and duration of symptoms. But in our cases statistical analysis revealed that grade I histology (p<0.025) and young age (p<0.001) were the most significant good prognostic variables.