Supratentorial low-grade glioma: is there a role for radiation therapy?

The supratentorial low-grade gliomas are a heterogeneous group of central nervous system tumours. Knowledge of their biology, primarily based on histologic subtype and patient age, is helpful in determining prognosis and guiding therapeutic recommendations. The pilocytic tumours usually occur in younger patients and carry a favourable prognosis. Recurrence following gross total excision is rare, and approximately 80% of patients undergoing subtotal removal with or without postoperative radiation therapy (RT) will survive 10 years or longer. In contrast, non-pilocytic, supratentorial low-grade tumours (including the diffuse fibrillary, protoplasmic and gemistocytic subtypes), as well as mixed oligoastrocytomas and oligodendrogliomas are infrequently cured, even with gross total excision. Survival benefit with postoperative RT has been suggested by several retrospective studies. When RT is prescribed, localized treatment fields are suggested for total doses of 4500 to 6500 cGy. Ongoing prospective, randomized studies hopefully will clarify the role of RT in these neoplasms, as well as the optimal dose.