To make a rational decision regarding the proper course of treatment for an adult with a supratentorial low-grade glioma, the physician must understand the pathology, natural history, and modern treatment options. In this regard, three commonly held beliefs may lead to the policy of routine observation,1 which may be inappropriate.
The first commonly held belief is that low-grade gliomas are a homogeneous group of neoplasms. In fact, they are not. Recent studies have divided the low-grade gliomas into two distinct groups, the pilocytic astrocytomas and the ordinary astrocytomas (including oligoastrocytomas and oligodendrogliomas). Patients with pilocytic astrocytomas enjoy 10-year survivals of 80% or more following complete or even incomplete excision.24 On the other hand, ordinary astrocytomas are associated with 10-year survivals of 20%.
This dismal prognosis challenges the second commonly held belief, which is that low-grade gliomas are benign5-6 or indolent.1 In an earlier study from my
Shaw EG. Low-Grade Gliomas: To Treat or Not to Treat?A Radiation Oncologist's Viewpoint. Arch Neurol. 1990;47(10):1138–1139. doi:10.1001/archneur.1990.00530100108023