Adjuvant Therapies for Supratentorial Low-Grade Gliomas in Children

The ideal treatment for LGGs is complete surgical resection. However, this may not always be possible. When there is residual tumor or the location does not allow more than a biopsy, further treatment is controversial. Some tumors progress very quickly, others grow more slowly, others remain stable for many years, and others may even regress without treatment. Consequently, management should consider both treatment of symptoms and long-term control of the tumor as the child grows.

Radiotherapy

Radiotherapy may cause cognitive and/or endocrinological alterations, radionecrosis, or malignant changes (17). The problem is deciding when to give radiotherapy, what the effective dose will be for the type of LGG being treated, and how the patient will tolerate the treatment. The complications of radiotherapy are related to age and volume of brain radiated, with younger children having higher morbidity rates. Hence, in young children, chemotherapy is often preferred to radiotherapy (18).

• Type of radiation: In newer types of radiotherapy, “focal or conformal” treatments are administered to LGGs without damage to neighboring cerebral tissue. Examples of such treatments are stereotactic radiotherapy, intensity-modulated radiotherapy (IMRT), image-guided radiotherapy, and proton-beam therapy (17). Stereotactic radiosurgery (a single, very elevated necrosing dose of radiation) has also been used to treat LGG recurrence.
• Age limits for use of radiation: Radiotherapy is generally not used in patients younger than 3 years of age; and, unless there are no other options, radiotherapy is avoided up to the age of about 7 years. With the newer forms of conformal radiotherapy (including stereotactic radiotherapy) some consideration is being given to using focal radiotherapy in younger children (19).
• Timing of radiotherapy or chemotherapy: Radiotherapy and chemotherapy are generally not recommended immediately after the complete or near complete resection of a tumor. In such patients, radiotherapy or chemotherapy is considered if the tumor recurs or progresses, often after further surgery. However, patients with unresectable tumors are considered for radiotherapy or chemotherapy immediately after surgery when there is a high risk for progression.

Chemotherapy

• Temozolomide: The classic combination of procarbazine, lomustine (CCNU), and vincristine has been replaced by temozolomide due to its easy administration and reduced toxicity. When used as first-line treatment for LGGs, temozolomide has achieved good results in 31–61% of cases (20). Temozolomide has also been found to improve the prognosis in patients treated with radiotherapy (19).
• Oligodendrogliomas: Excellent results (90%) have been obtained with procarbazine and temozolomide in the treatment of oligodendroglioma recurrence and in anaplastic oligodendrogliomas (19).