Glioblastoma revisited: do clinical observations match basic science theory? Radiosurgery: clinical observations

Protective effect on normal brain tissue during a combinational therapy of 2-deoxy-d-glucose and hypofractionated irradiation in malignant gliomas

Purpose:

To investigate the effect of 2-deoxy–D-glucose (2-DG), an inhibitor of glucose transport and glycolysis, on glioblastoma and the normal brain tissue during combined treatment with hypofractionated radiotherapy.

Materials and Methods:

Twenty patients with malignant gliomas (18 Glioblastoma Multiformae, 2 Anasplastic Astrocytoma grade III) following surgery were treated weekly (once) with 2-DG, (250 mg/kg body weight), followed by 5 Gy of radiation to the tumor bed per fraction for 7 weeks. Clinical evaluation, complete hemogram, and random blood sugar levels were carried out in each cycle. Follow-up computed tomography (CT)/magnetic resonance imaging (MRI) was done to evaluate radiation-induced changes. Kernofsky Performance scale (KPS) was recorded preoperatively; postoperatively, and post-therapy till the last follow-up.

Results:

Twenty patients were recruited for this trail; 19 of them completed the treatment and 1 discontinued. The survival period ranged between 6 and 36 months after the treatment, with a median survival of 14 months. CT and MRI revealed significant tumor necrosis. Histological evidence from the tissue during reexploration confirms the hypothesis of protective effect of 2-DG on normal brain. KPS was above 80% in majority of the patients, 6 months after the surgery.

Conclusion:

Radiotherapy coupled with 2-DG enhances tumor necrosis selectively and significantly while the normal brain gets relatively protected. This has been reflected in our study both clinically by preservation of quality-of-life and pathologically by retaining the integrity of normal brain architecture.

Recurrent high-grade glioma

OPINION STATEMENT

Opinions vary on the best treatment options for recurrent high-grade glioma. Some argue that bevacizumab should become standard of care for patients with recurrent glioblastoma, especially in light of recent FDA approval for this indication. However, this opinion is not uniformly accepted. Age, performance status, histology, tumor size and location, O6-methylguanine-DNA methyltransferase (MGMT) methylation status for glioblastoma, 1p/19q status for oligodendroglial tumors, and the number and types of prior therapies are important considerations. In addition, recurrent disease must be distinguished from "pseudoprogression" due to treatment effects. Enrollment in a clinical trial is the optimal choice for most patients with recurrent high-grade glioma after failure of radiation therapy and temozolomide. For patients who are ineligible or do not have access to clinical trials, then either bevacizumab monotherapy or bevacizumab in combination with a second agent such as irinotecan is recommended. Involved-field external beam radiation should be considered for patients with anaplastic gliomas who have not received radiation. For patients with anaplastic astrocytoma who progress after radiotherapy, temozolomide may be used. For patients with anaplastic oligodendroglioma who progress after radiotherapy, PCV chemotherapy and temozolomide are options. Oligodendroglial tumors with 1p/19q deletions are more likely to respond to treatment. In the past, carmustine was commonly used to treat recurrent high-grade glioma, but the utility of carmustine in the modern era is unknown because most studies were performed prior to the widespread use of temozolomide. High-precision re-irradiation such as stereotactic radiosurgery is another option in high-grade glioma, especially for patients with poor bone marrow reserve or inability to tolerate chemotherapy, but there is a paucity of studies with adequate controls. Surgery may be useful as adjuvant treatment for patients with symptoms due to mass effect or for patients requiring definitive histopathology, but it generally should be combined with another treatment modality. Emerging therapies, including dose-intense temozolomide regimens, targeted molecular inhibitors, other antiangiogenic therapies, viral gene therapies, immunotherapies, and convection-enhanced delivery of targeted immunotoxins, are still under investigation.

Radiosurgery for primary malignant brain tumors

Despite the ability of surgery, radiotherapy, and chemotherapy to prolong survival in patients with glioblastoma multiforme (GBM), most patients succumb to their disease, usually as a result of local tumor persistence or recurrence. Stereotactic radiosurgery (SRS) allows a substantial increase in total dose at sites of greatest tumor cell density while sparing most of the normal brain, resulting in significantly improved survival. SRS was designed as a technique to deliver a large single dose of radiation to a small and focal target: two of its hallmarks are the focal distribution of dose and the inverse relationship between dose and volume. Acute complications of SRS are related to edema and are manifested as a worsening of pre-existing symptoms: seizure, aphasia, and motor deficits--these are treatable with steroids and are transient in the majority of cases. The actuarial risk of undergoing reoperation was 33% at 12 months and 48% at 24 months, following SRS. Patterns of failure were similar following brachytherapy or SRS as treatment for recurrent GBM with most patients experiencing marginal failure outside the original treatment volume. Patients with small (< 30 mm diameter), radiographically distinct and focally recurrent GBM should be considered for SRS. Larger lesions (> 30 mm diameter), especially those adjacent to eloquent cortex or critical white matter pathways, must be evaluated with caution. The potential for acute toxicity associated with SRS increases substantially for larger lesions. There is a significant survival advantage using SRS in many patients with gliomas, especially if appropriately used with surgery and other adjuvant therapy.

Improving cancer radiotherapy with 2-deoxy-D-glucose: phase I/II clinical trials on human cerebral gliomas

PURPOSE

Evaluation of tolerance, toxicity, and feasibility of combining large fraction (5 Gy) radiotherapy with 2-deoxy-D-glucose (2DG), an inhibitor of glucose transport and glycolysis, which has been shown to differentially inhibit repair of radiation damage in cancer cells.

METHODS AND MATERIALS

Twenty patients with supratentorial glioma (Grade 3/4), following surgery were treated with four weekly fractions of oral 2DG (200 mg/kg body weight) followed by whole brain irradiation (5 Gy). Two weeks later, supplement focal radiation to the tumor (14 Gy/7 fractions) was given. Routine clinical evaluation, x-ray computerized tomography (CT), and magnetic resonance (MR) imaging were carried out to study the acute and late radiation effects.

RESULTS

All the 20 patients completed the treatment without any interruption. The vital parameters were within normal limits during the treatment. None reported headache during the treatment. Mild to moderate nausea and vomiting were observed during the days of combined therapy (2DG + RT) in 10 patients. No significant deterioration of the neurological status was observed during the treatment period. Seven patients were alive at 63, 43, 36, 28, 27, 19, and 18 months of follow-up. In these patients, the clinical and MR imaging studies did not reveal any late radiation effects.

CONCLUSIONS

Feasibility of administering the treatment (2DG + 5 Gy) is demonstrated by the excellent tolerance observed in all 20 patients. Further, the clinical and MR studies also show the absence of any brain parenchymal damage.