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| | ORIGINAL ARTICLE | | | | | Year : 2009 | Volume : 5 | Issue : 9 | Page : 44-47 | | | Differential responses of tumors and normal brain to the combined treatment of 2-DG and radiation in glioablastoma
Venkatesh K Prasanna1, Neelam K Venkataramana2, BS Dwarakanath3, Vani Santhosh4
1 Manipal Institute for Neurological Disorders, Bangalore, India
2 Advanced Neuroscience Institute, BGS Global Hospital, Bangalore, India
3 Institute of Nuclear Medicine and Allied Sciences, New Delhi, India
4 National Institute of Mental Health and Neurosciences, Bangalore, India
| Date of Web Publication | 21-Aug-2009 | Correspondence Address:
B S Dwarakanath
Institute of Nuclear Medicine and Allied Sciences, New Delhi 110 054
India
DOI: 10.4103/0973-1482.55141 PMID: 20009294
2-deoxy-D-glucose (2-DG), an inhibitor of glucose transport and glycolysis, enhances radiation damage selectively in tumor cells by modulating damage response pathways resulting in cell death in vitro and local tumor control. Phase I and II clinical trials in patients with malignant glioma have shown excellent tolerance to a combined treatment of orally administered 2-DG and hypofractionated radiotherapy without any acute toxicity and late radiation damage. Phase III efficacy trials are currently at an advanced stage. Re-exploratory surgery performed in 13 patients due to persistent symptoms of elevated ICP and mass effect at different follow-up periods revealed extensive tumor necrosis with well-preserved normal brain tissue adjoining the tumor included in the treatment volume as revealed by a histological examination. These observations are perhaps the first clinical evidences for differential effects of 2-DG on tumors and normal tissues in conformity with earlier in vitro and in vivo studies in normal and tumor-bearing mice.
Keywords: Malignant gliomas, neural protection, radiotherapy, radionecrosis, quality of life, 2-deoxy-D-glucose
How to cite this article:
Prasanna VK, Venkataramana NK, Dwarakanath B S, Santhosh V. Differential responses of tumors and normal brain to the combined treatment of 2-DG and radiation in glioablastoma. J Can Res Ther 2009;5:44-7 |
How to cite this URL:
Prasanna VK, Venkataramana NK, Dwarakanath B S, Santhosh V. Differential responses of tumors and normal brain to the combined treatment of 2-DG and radiation in glioablastoma. J Can Res Ther [serial online] 2009 [cited 2014 Feb 28];5:44-7. Available from: http://www.cancerjournal.net/text.asp?2009/5/9/44/55141 |
| > Introduction | |  |
The prognosis of patients suffering from malignant cerebral gliomas has remained dismal, despite utilization of multimodal therapies and advances in radiation technology. [1] Failure of radiotherapy in cerebral gliomas is mainly attributed to the presence of hypoxic, repair proficient, and intrinsically radioresistant subpopulation of cells, [2],[3] resulting in regrowth following therapy. [1] On the other hand, delivery of high doses of radiation has limitations due to the damage to surrounding normal brain tissue. [4] Based on the bioenergetics of damage response in cell and differences in the glucose metabolism between tumor and normal cells, it has been suggested that inhibitors of glucose transport and glycolysis could differentially enhance radiation damage in tumor cells. [5] A number of studies have indeed demonstrated that the presence of2-deoxy-D-glucose (2-DG), an inhibitor of glucose transport and glycolysis, prior to radiation selectively inhibits prosurvival processes, thereby enhancing the radiation damage in tumor cells under euoxic as well as hypoxic conditions. [6] Therefore, a combination of ionizing radiation with 2-DG provides a unique opportunity to selectively destroy tumors by differentially enhancing the radiation damage in cancer cells and preventing radiation damage to normal tissue at the same time. Phase I and II clinical trials in malignant glioma patients have shown excellent tolerance to a combined treatment of orally administered 2-DG and hypofractionated radiotherapy without any acute toxicity and late radiation damage. [7],[8] Phase III efficacy trials are currently at an advanced stage. High-grade gliomas continue to grow irrespective of surgery and adjuvant therapy leading to progressive deterioration in their clinical condition. Mean survival of patients with glioblastoma multiformae is 14.6 months with surgery, radiotherapy, and temozolamide therapy. [9] In our series, 13 patients continued to have symptoms of raised intracranial pressure, and repeat imaging showed persistent mass effect warranting re-exploration. At surgery, there was extensive tumor necrosis in the center with a peripheral firm gliomesenchymal scar demarcating the normal brain. The adjacent normal brain was looking normal. The excision of the junctional areas has included the normal structures of the brain at within the field of radiotherapy. Histopathologically, these areas have shown an intact architecture and blood vessels.
| > Materials and Methods | | |
The present study was conducted after clearance from the Institutional Ethics Committee of Manipal Hospital, Bangalore, and approval of the drug controller general, Ministry of Health and Family Welfare, India. Twenty patient (13 males and 7 females) in the age group of 27-67 years with malignant gliomas were studied. The preoperative Kernofsky performance scale (KPS) was more than 70. After scrutinizing the inclusion criteria, informed consent was obtained and treatment was provided between December 2001 and March 2004. Hematological investigations, liver function test, renal function test, and contrast CT scans were performed preoperatively, postoperatively, postradiotherapy, and during follow-up every 3 months. Macroscopic near-total removal was done in five, while three underwent subtotal resection and only diagnostic biopsy in two deep-seated lesions.
After an overnight fasting, aqueous solution (100 ml) of 2-DG, at a dose of 250 mg/kg, was administered orally, 25min before focal irradiation of the tumor with a linear accelerator. The radiation dose was 5 Gy per fraction by two parallel opposing lateral portals. Radiation was given to the tumor bed and 3cm around the tumor margins. This schedule was given once a week for 7 weeks aiming to a total radiation of 35 Gy (biologically equivalent to 62 Gy in the conventional fraction). Tolerance to the treatment was assessed by vital parameters such as blood pressure, pulse rate, and respiratory rate that were monitored hourly on treatment days. KPS was measured throughout the treatment and follow-up period.
| > Results | | |
Among the 20 who fulfilled inclusion criteria, 13 were males and 7 were females aged between 27 and 67 years; 18 had GBM and 2 had astrocytomas grade III. The mean survival rate of these patients was 12.6 months. KPS was measured at preoperative, postoperative, post-RT and during follow-up. KPS improved in 12, remained same in 2, and decreased in 6 patients over the period of 6 months from the time of surgery. Improvement in KPS suggested preserved or enhanced quality of life (QOL)/general condition in this trail group. A total of 13 out of 20 patients developed symptoms of raised ICP at an interval ranging from 3 to 9 months post-RT. Hence re-exploration was performed. Intraoperatively, tumor was soft, necrotic, and suckable. After debulking, the patients have shown clinical improvement.
Histology
Histological examination of the tissue obtained from re-exploratory surgery revealed severe tumor necrosis, and hyalinization of blood vessels with a gliomesenchymal scar at the junction of the brain with adjacent, totally preserved choroids plexus. The combined treatment (2-DG + RT) induced sheets of necrosis in the tumor, which was classical in appearance [Figure 1]. We also observed significant number of giant cells significance of which is not clearly understood at present. However, we feel that it could be a reaction to the necrotic tissue. There seems to be a clear mesenchymal scar separating this from the surrounding brain. In four specimens, we had the opportunity to examine surrounding brain and choroid plexus adjacent to the tumor well within the field of radiation. This clearly demonstrates the total preservation of the architecture of the mucosa of the choroid plexus, suggesting a protective effect of 2-DG on the normal brain tissue and is in confirmation with the observations in vitro [10] and in vivo studies in mice. [11] The administration of 2-DG has a dual effect on tumor cells and normal cells. Postradiation changes were seen only at the tumor bed, not affecting the normal brain structures.
| > Discussion | | |
The present study demonstrated that the combination of 2-DG with hypofractionated regimen has the potential to induce extensive tumor necrosis (contributing to local tumor control) and also protect the normal brain tissue, contributing to the maintenance or improvement in the QOL.
Surgical re-exploration carried out in the present studies provided an opportunity to obtain a detailed histological examination of the tissue in the irradiated volume. Interestingly enough, we found extensive tumor necrosis, and the preservation of the surrounding normal brain tissue, mainly the choroid plexus, which corroborated with the radiological findings [Figure 1]. This perhaps is the first study providing direct clinical and histopathological evidence of a differential effect of 2-DG between tumor and normal tissues. Earlier in vitro studies in human PBL, [10] ex vivo studies with mouse splenocytes and thymocytes [12] as well as in vivo studies in whole-body irradiated mice have shown protection against radiation-induced cytogenetic damage and apoptosis by 2-DG. [11]
The reasons for the well-preserved normal tissue observed could be the lower physical dose of 35 Gy used here (7 × 5 Gy/fraction), although it is biologically equivalent (BED) to a dose of 62 Gy (with a a/b value of 3 for a normal brain and 10 for the tumor) in the conventional fractionation (5 fractions per week of 2 Gy/fraction is administered for 30 fractions). Alternatively, it could also be due to reductions in the manifestations of radiation-induced primary lesions and metabolic oxidative stress that lead to delayed tissue damage. At therapeutically relevant and related doses, radiation mainly induces mitosis with minimal apoptotic death leading to secondary necrosis in proliferating epithelial cells and epithelial tumor cells. [13] Although the late radiation-induced necrosis of the normal brain tissue is not completely understood, it appears to be related to inflammatory response involving aberrant cytokine secretion. [14] Consequently, in nonproliferating cells of the normal brain tissue, apoptosis is likely to be a major contributor to the treatment-induced tissue damage. Therefore, it appears that the inhibition of radiation-induced apoptosis by 2-DG in the normal brain tissue and the restoration of normal cytokine profile are the contributing factors for the well-preserved normal tissue architecture observed in these studies. Recent studies on human glioma cells (U-87) have shown 2-DG-induced changes in the expression of certain genes related to apoptosis and alterations in the immune status including cytokine secretion in tumor-bearing mice. [15],[16] Further studies are required to understand the mechanisms underlying the protection of normal tissue damage, as it would allow the use of higher radiation doses for achieving better therapeutic efficacy. Most recently, glucose deprivation induced either by glucose withdrawal or addition of 2-DG has been found to enhance apoptosis in glioblastoma cells, but not in normal astrocytes, that could be linked to the maintenance of ATP levels and redox status in astrocytes. [17]
| > Conclusion | | |
2-DG with radiotherapy enhances tumor necrosis significantly and relatively protects the surrounding normal brain. This has been reflected in our study clinically as the preservation of QOL and histopathologically as the preservation of the normal brain architecture. The evaluation of the mechanisms of the development or aggravation of late cerebral radionecrosis requires a further study for abnormal cytokine secretions and aberrant inflammatory reactions.
| > Acknowledgement | | |
This paper was presented at the Symposium on "Applications of2-deoxy-D-glucose in the management of cancer," Institute of Nuclear Medicine and Allied Sciences, New Delhi, India, November 8-10, 2006.[Figure 2]
| > References | | |
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[Figure 1], [Figure 2]
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