Extent of resection and survival in glioblastoma multiforme: identification of and adjustment for bias

Abstract

Treatment bias was demonstrated regarding resection and second-line therapies. However, bias and imbalances were controllable in the cohorts available from the 5-aminolevulinic acid study so that the present data now provide Level 2b evidence (Oxford Centre for Evidence-based Medicine) that survival depends on complete resection of enhancing tumor in glioblastoma multiforme.