Low-grade gliomas: answering one question in a myriad of new questions

The role of radiotherapy in the management of patients with diffuse low grade glioma: A systematic review and evidence-based clinical practice guideline

QUESTIONS

(1) What is the optimal role of external beam radiotherapy in the management of adult patients with newly diagnosed low-grade glioma (LGG) in terms of improving outcome (i.e., survival, complications, seizure control or other reported outcomes of interest)? (2) Which radiation strategies (dose, timing, fractionation, stereotactic radiation, brachytherapy, chemotherapy) improve outcomes compared to standard external beam radiation therapy in the initial management of low grade gliomas in adults? (3) Do specific factors (e.g., age, volume, extent of resection, genetic subtype) identify subgroups with better outcomes following radiation therapy than the general population of adults with newly diagnosed low-grade gliomas?

TARGET POPULATION

These recommendations apply to adults with newly diagnosed diffuse LGG.

RECOMMENDATIONS

OUTCOMES IN ADULT PATIENTS WITH NEWLY DIAGNOSED LOW GRADE GLIOMA TREATED WITH RADIOTHERAPY: Level I Radiotherapy is recommended in the management of newly diagnosed low-grade glioma in adults to prolong progression free survival, irrespective of extent of resection. Level II Radiotherapy is recommended in the management of newly diagnosed low grade glioma in adults as an equivalent alternative to observation in preserving cognitive function, irrespective of extent of resection. Level III Radiotherapy is recommended in the management of newly diagnosed low grade glioma in adults to improve seizure control in patients with epilepsy and subtotal resection. Level III Radiotherapy is recommended in the management of newly diagnosed low-grade glioma in adults to prolong overall survival in patients with subtotal resection. Level III Consideration of the risk of radiation induced morbidity, including cognitive decline, imaging abnormalities, metabolic dysfunction and malignant transformation, is recommended when the delivery of radiotherapy is selected in the management of newly diagnosed low-grade glioma in adults. STRATEGIES OF RADIOTHERAPY IN ADULT PATIENTS WITH NEWLY DIAGNOSED LOW GRADE GLIOMA: Level I Lower dose radiotherapy is recommended as an equivalent alternative to higher dose immediate postoperative radiotherapy (45-50.4 vs. 59.4-64.8 Gy) in the management of newly diagnosed low-grade glioma in adults with reduced toxicity. Level III Delaying radiotherapy until recurrence or progression is recommended as an equivalent alternative to immediate postoperative radiotherapy in the management of newly diagnosed low-grade glioma in adults but may result in shorter time to progression. Level III The addition of chemotherapy to radiotherapy is not recommended over whole brain radiotherapy alone in the management of low-grade glioma, as it provides no additional survival benefit. Level III Limited-field radiotherapy is recommended over whole brain radiotherapy in the management of low-grade glioma. Level III Either stereotactic radiosurgery or brachytherapy are recommended as acceptable alternatives to external radiotherapy in selected patients. PROGNOSTIC FACTORS IN ADULT PATIENTS WITH NEWLY DIAGNOSED LOW GRADE GLIOMA TREATED WITH RADIOTHERAPY: Level II It is recommended that age greater than 40 years, astrocytic pathology, diameter greater than 6 cm, tumor crossing the midline and preoperative neurological deficit be considered as negative prognostic indicators when predicting overall survival in adult low grade glioma patients treated with radiotherapy. Level II It is recommended that smaller tumor size, extent of surgical resection and higher mini-mental status exam be considered as positive prognostic indicators when predicting overall survival and progression free survival in patients in adult low grade glioma patients treated with radiotherapy. Level III It is recommended that seizures at presentation, presence of oligodendroglial histological component and 1p19q deletion (along with additional relevant factors-see Table 1) be considered as positive prognostic indicators when predicting response to radiotherapy in adults with low grade gliomas. Level III It is recommended that increasing age, decreasing performance status, decreasing cognition, presence of astrocytic histological component (along with additional relevant factors (see Tables 1, 2) be considered as negative prognostic indicators when predicting response to radiotherapy.

The changing management of low-grade astrocytomas and oligodendrogliomas

Low-grade gliomas are uncommon primary brain tumors that preferentially affect young to middle-aged adults. Although they are indolent tumors, low-grade gliomas cause considerable and progressive morbidity and are ultimately fatal. Surgery and radiotherapy are the primary therapeutic options for patients with these diseases. Chemotherapy is playing a larger role in the management of patients with low-grade gliomas. Patients with oligodendrogliomas or other low-grade gliomas that harbor a distinct genetic derangement characterized by allelic loss of chromosomes 1p and 19q appear to have a superior prognosis that is due in part to a more predictable and durable response to treatment. For this subset of patients with low-grade gliomas, treatment with initial chemotherapy and deferred radiotherapy is an increasingly attractive therapeutic approach.

Radiation induced adult medulloblastoma: a case report

Adult medulloblastoma is a rare intracranial tumor. Our patient is a 61 year old woman treated with cranial irradiation 15 years previously for a low grade astrocytoma in the left posterior temporal lobe that was recently diagnosed with medulloblastoma in the right cerebellum. This is the first reported case of radiation induced adult medulloblastoma.

Oligodendroglioma

Surgery, radiotherapy, and chemotherapy are the standard treatment modalities for all primary brain tumors. Oligodendroglial tumors are uncommon primary brain tumors that typically are classified as low-grade or anaplastic based on their histologic appearance. A great deal of controversy has surrounded the diagnosis of an oligodendroglioma because no unique immunohistochemical marker exists to diagnose this tumor, forcing pathologists to render a diagnosis based on subjective microscopic features. Although once considered relatively rare, oligodendroglial tumors have been increasing in incidence because pathologists have become less rigorous about this diagnosis. However, recent advances in our understanding of the molecular genetic changes associated with brain tumors have identified loss of heterozygosity of chromosomes 1p and 19q as a unique genetic signature of most oligodendroglial tumors, an advance that has paved the way for pathologists to use molecular diagnostics to identify these tumors with improved reliability. These genetic derangements have significant clinical and therapeutic implications because they have been associated with a predictable and durable response to treatment, particularly chemotherapy, and an improved prognosis. The unique chemosensitivity of oligodendroglial tumors has been recognized by neurooncologists for at least 15 years, and various chemotherapeutic agents have been used to manage these diseases. However, the appropriate timing of chemotherapy, and the drugs of choice remain controversial. Increasingly, neurooncologists are reluctant to use radiotherapy as initial management for these diseases because of concerns surrounding the late neurocognitive sequelae of cranial irradiation. These toxicities are particularly important for patients with low-grade oligodendrogliomas in whom the prognosis often exceeds 10 years. Consequently, with the accumulating evidence supporting the chemosensitivity of low-grade and anaplastic oligodendrogliomas and the recent ability to use molecular diagnostics to identify a chemosensitive subset of oligodendrogliomas, neurooncologists are increasingly administering chemotherapy as the initial intervention for all oligodendroglial tumors that harbor favorable genetic derangements. Additionally, although immediate postoperative treatment is uniformly administered to patients with anaplastic oligodendrogliomas, there has been an increasing tendency to defer definitive therapy for those with low-grade oligodendrogliomas until evidence of progression. The development of temozolomide, an oral and well-tolerated alkylating agent that has activity against oligodendroglial tumors, has accelerated this trend to the extent that currently many patients with newly diagnosed low-grade and anaplastic oligodendrogliomas are offered this drug as initial treatment. This paper reviews the current management of oligodendrogliomas, with an emphasis on the expanding role of chemotherapy for these neoplasms.

Progress in clinical neurosciences: Advances in the management of low-grade gliomas

The management of low-grade gliomas represents one of the most challenging and controversial areas in neuro-oncology. Many aspects of the treatment of low-grade gliomas are debated, including the optimal timing of surgery and radiotherapy, the benefit of extensive surgery, and the impact of these variables on the natural history of these indolent and generally incurable tumours. The recently published results of several large multicentre trials addressing the timing and dose of radiotherapy have provided solid evidence for delayed and reduced dose irradiation. These studies have also confirmed prognostic variables that can be used to guide management of individual patients. Among these variables is the observation that tumours with oligodendroglial features have a better natural history and response profile. The recognition that as many as two thirds of low-grade gliomas have oligodendroglial features, advances in molecular diagnostics making accurate pathologic diagnosis of oligodendroglial tumours possible, and the established chemosensitivity of malignant oligodendrogliomas, have raised new issues surrounding the potential value of chemotherapy for low-grade gliomas. This review will be restricted to low-grade diffuse astrocytomas, oligodendrogliomas, and low-grade mixed oligoastrocytomas in adults, and provide evidence-based guidelines for the management of these tumours, including the emerging role of chemotherapy as initial treatment.

Hyperfractionated radiation therapy for incompletely resected supratentorial low-grade glioma: a 10-year update of a phase II study

PURPOSE

To provide a 10-year update of hyperfractionated radiation therapy (Hfx RT) in adults with incompletely resected supratentorial low-grade glioma.

METHODS AND MATERIALS

A total of 37 patients were treated with 55 Gy in 50 fractions in 25 treatment days in 5 weeks to tumor plus 2 cm, and additional 17.6 Gy given in 16 fractions in 8 treatment days in 1.5 weeks to tumor plus 1 cm, (1.1 Gy twice daily). Total dose was 72.6 Gy in 66 fractions in 33 treatment days in 6.5 weeks.

RESULTS

After a median follow-up time of 121 months for all patients, the median survival time (MST) for all 37 patients was 145 months, whereas 10-year survival rate was 67%. Median time to tumor progression (MTP) has not yet been attained, but 10-year progression-free survival (PFS) rate was 62%. There was no difference in survival or PFS regarding gender, age, location, site, size, CT enhancement, and histology; whereas lower KPS, higher neurologic status, and lesser extent of surgery had an adverse influence. Infield progression occurred in 15 (88%), whereas in only 2 (12%) patients, tumor progression was described as marginal. Brain necrosis has not been observed so far. Autopsy findings confirmed recurrent glioma and excluded post-RT necrosis in 14 (38%) patients. Of those, 7 (50%) patients had either Grade 3 (n = 4) or Grade 4 (n = 3) glioma.

CONCLUSION

High-dose HFX RT is effective with mild to moderate toxicity. Further studies are warranted with more patients before testing it against standard fractionation RT in this patient population.