Radical surgery in the management of low-grade and high-grade gliomas

The question of whether radical resection of low-grade gliomas results in enhanced patient outcome cannot be answered with certainty. This uncertainty stems from methodological problems inherent in retrospective studies which consist of relatively small numbers of selected patients lacking uniform prognostic or adjuvant treatment profiles and where EOR is determined mainly by subjective measures. These limitations aside, greater EOR for astrocytoma is found to be significantly associated with longer survival in about half of the studies that analyse exclusive sets of CT-era patients using multivariate analysis. Studies that find surgery to be significant tend to include larger numbers of patients. A possible explanation for this association is that larger studies reduce the variance within the subgroups of EOR patients, allowing for more meaningful statistical analysis. There is no large CT-era review of EOR and outcome for oligodendroglioma patients analysed by multivariate methods; however, the pre-CT and mixed pre- and post-CT-era data mainly support maximal EOR for these lesions. Other end points, such as time to tumour progression, frequency of malignant progression and duration of high-quality survival are much less well-documented. One study concluded that deferral of therapy at the time of diagnosis did not reduce time to malignant progression or survival (Recht et al, 1992) while another study correlated greater EOR and less residual tumour with prolonged progression-free survival and lower rates of malignant progression (Berger et al, 1994). Mortality and morbidity have not been analysed by EOR, but must be considered when recommending radical surgery over other treatment options. The extent of tumour resection for hemispheric GBMs, as well as anaplastic gliomas, significantly affects outcome with regard to post-operative KPS, TTP and survival. By prolonging life at the same or better quality of existence, time is gained that may allow for the institution of different adjuvant treatment modalities. This may be particularly critical for new strategies, such as gene therapy or antisense oligodeoxynucleotides that block mRNA translation of specific regulatory proteins, that may function more effectively against a smaller volume of residual tumour.