Radiotherapy For Glioma Research Articles

When should radiotherapy for low-grade glioma be given—immediately after surgery or at the time of progression?

When should radiotherapy for low-grade glioma be given—immediately after surgery or at the time of progression?

Should radiotherapy for low-grade glioma be given immediately after surgery or at the time of progression?

Should radiotherapy for low-grade glioma be given immediately after surgery or at the time of progression?

Intensity-modulated radiotherapy in high-grade gliomas: Clinical and dosimetric results

To report preliminary clinical and dosimetric data from intensity-modulated radiotherapy (IMRT) for malignant gliomas. Fifty-eight consecutive high-grade gliomas were treated between January 2001 and December 2003 with dynamic multileaf collimator IMRT, planned with the inverse approach. A dose of 59.4-60 Gy at 1.8-2.0 Gy per fraction was delivered. A total of three to five noncoplanar beams were used to cover at least 95% of the target volume with the prescription isodose line. Glioblastoma accounted for 70% of the cases, and anaplastic oligodendroglioma histology (pure or mixed) was seen in 15% of the cases. Surgery consisted of biopsy only in 26% of the patients, and 80% received adjuvant chemotherapy. With a median follow-up of 24 months, 85% of the patients have relapsed. The median progression-free survival time for anaplastic astrocytoma and glioblastoma histology was 5.6 and 2.5 months, respectively. The overall survival time for anaplastic glioma and glioblastoma was 36 and 9 months, respectively. Ninety-six percent of the recurrences were local. No Grade IV/V late neurologic toxicities were noted. A comparative dosimetric analysis revealed that regardless of tumor location, IMRT did not significantly improve target coverage compared with three-dimensional planning. However, IMRT resulted in a decreased maximum dose to the spinal cord, optic nerves, and eye by 16%, 7%, and 15%, respectively, owing to its improved dose conformality. The mean brainstem dose also decreased by 7%. Intensity-modulated radiotherapy delivered with a limited number of beams did not result in an increased dose to the normal brain. It is unlikely that IMRT will improve local control in high-grade gliomas without further dose escalation compared with conventional radiotherapy. However, it might result in decreased late toxicities associated with radiotherapy.

Dendritic cell therapy with improved outcome in glioma multiforme—A case report

Malignant gliomas are the most devastating tumors in clinical practice and have poorest survival. Immunological treatment of such patients may likely increase the survival and quality of life. Dendritic cells (DCs), most potent antigen presenting cells in combination with oral chemotherapeutic agents may be tried for patients giving consent to such treatment. We have successfully combined the two therapies in an adult male patient who was on downhill course after being operated on once with post operation chemotherapy and radiotherapy for glioma in the left parietal area. He received five dendritic cell therapy vaccines in combination with oral chemotherapy and responded dramatically having near normal quality of life for an additional five months with this regime, increasing the survival after operation to 11 months. This therapy is continuing with radiological betterment of the lesion. The DCs are matured with antigen extracted from wax embedded tissue at 6th day of culture. We feel that the treatment can be given to more number of patients to establish its efficacy for the dreaded cancer glioblastoma multiforme.

Radiation-Induced Osteosarcoma 16 Years After Surgery and Radiation for Glioma-Case Report-

A 35-year-old man developed osteosarcoma of the left parietal and occipital bones 16 years after radiotherapy for glioma in the right occipital lobe. Radiotherapy of the primary neoplasm used 50 Gy administered to a localized field through two lateral ports. The secondary neoplasm arose contralateral to the primary lesion but within the irradiated field. The tumor had a multilocular cyst with considerable intracranial extension, and symptoms of elevated intracranial pressure were prominent early in the course. After a short-lived initial remission following surgical intervention and chemotherapy, the patient deteriorated because of tumor recurrence and died 18 months after the diagnosis. Radiation-induced osteosarcoma is a well-known but rare complication of radiotherapy for brain neoplasms with a poor prognosis.

Dominant‐negative Rac increases both inherent and ionizing radiation‐induced cell migration in C6 rat glioma cells

Rho-like GTPases, including Cdc42, Rac1 and RhoA, regulate distinct actin cytoskeleton changes required for cell adhesion, migration and invasion. In the present study, we examined the role of Rac signaling in inherent migration, as well as radiation-induced migration, of rat glioma cells. Stable overexpression of dominant-negative Rac1N17 in a C6 rat glioma cell line (C6-RacN17) promoted cell migration, and ionizing radiation further increased this migration. Migration was accompanied by decreased expression of the focal adhesion molecules FAK and paxillin. Focal contacts and actin stress fibers were also reduced in C6-RacN17 cells. Downstream effectors of Rac include JNK and p38 MAP kinases. Irradiation transiently activated p38, JNK and ERK1/2 MAP kinases in C6-RacN17 cells, while p38 and JNK were constitutively activated in C6 control cells. Blocking JNK activity with JNK inhibitor SP600125 inhibited migration, suggesting that the JNK pathway may regulate radiation-induced, as well as inherent, migration of C6-RacN17 cells. Additionally, the radiation-induced migration increase was also inhibited by SB203580, a specific inhibitor of p38 MAP kinase. However, PD98059, a MEK kinase 1 inhibitor, failed to influence migration. This is the first evidence that suppression of Rac signaling may be involved in invasion or metastasis of glioma cells before and/or after radiotherapy. These data further suggest that radiotherapy for malignant glioma needs to be used with caution because of the potential for therapy-induced cell migration or invasion and that pharmacological inhibition of cell migration and invasion through targeting the Rac signaling pathway may represent a new approach for improving the therapeutic efficacy of radiotherapy for malignant glioma.

Role of radiotherapy in the treatment of gliomas

Malignant gliomas are challenging tumors that are often treated with a multimodality approach. This article focuses on the role of radiotherapy in the management of these tumors. The role of radiotherapy in low-grade gliomas remains controversial and this review focuses on the importance of prognostic factors, recent randomized trials involving radiotherapy, and toxicity from radiotherapy. In terms of high-grade gliomas, radiotherapy has a more established role and this review will address methods that have been evaluated in order to improve radiotherapy outcome. Improvements in radiotherapy delivery, tumor imaging and biologic modifiers may ultimately lead to improved outcome in the treatment of these difficult tumors.

Long-term efficacy of early versus delayed radiotherapy for low-grade astrocytoma and oligodendroglioma in adults: the EORTC 22845 randomised trial

Postoperative policies of "wait-and-see" and radiotherapy for low-grade glioma are poorly defined. A trial in the mid 1980s established the radiation dose. In 1986 the EORTC Radiotherapy and Brain Tumor Groups initiated a prospective trial to compare early radiotherapy with delayed radiotherapy. An interim analysis has been reported. We now present the long-term results. After surgery, patients from 24 centres across Europe were randomly assigned to either early radiotherapy of 54 Gy in fractions of 1.8 Gy or deferred radiotherapy until the time of progression (control group). Patients with low-grade astrocytoma, oligodendroglioma, mixed oligoastrocytoma, and incompletely resected pilocytic astrocytoma, with a WHO performance status 0-2 were eligible. Analysis was by intention to treat, and primary endpoints were overall and progression-free survival. 157 patients were assigned early radiotherapy, and 157 control. Median progression-free survival was 5.3 years in the early radiotherapy group and 3.4 years in the control group (hazard ratio 0.59, 95% CI 0.45-0.77; p<0.0001). However, overall survival was similar between groups: median survival in the radiotherapy group was 7.4 years compared with 7.2 years in the control group (hazard ratio 0.97, 95% CI 0.71-1.34; p=0.872). In the control group, 65% of patients received radiotherapy at progression. At 1 year, seizures were better controlled in the early radiotherapy group. Early radiotherapy after surgery lengthens the period without progression but does not affect overall survival. Because quality of life was not studied, it is not known whether time to progression reflects clinical deterioration. Radiotherapy could be deferred for patients with low-grade glioma who are in a good condition, provided they are carefully monitored.

12 Years’ Experience with Intraoperative Radiotherapy (IORT) of Malignant Gliomas

Even after surgery and radiotherapy, malignant gliomas still have a poor prognosis. The authors report on their experience with IORT in 71 patients. From May 1992 to February 2004, 71 patients with malignant gliomas were treated with IORT. 26 patients suffered from grade III gliomas, 45 patients from glioblastomas (GBM). IORT was carried out using a standard electron tube and 9- to 18-MeV electrons. 52/71 patients who were primarily treated received 20 Gy IORT + 60 Gy postoperative radiotherapy, 19/71 patients with recurrences only received IORT (20-25 Gy). The complication rates were 1.4% for wound infections and 5.6% for hemorrhage. Median disease-specific survival amounted to 14.9 months (gliomas III) and 14.2 months (GBM). The 2-year survival rates amounted to 26.9% (gliomas III) and 6.8% (GBM; p = 0.0296). Total versus subtotal resection had no significant influence on survival (p = 0.0741), nor had age, sex, tumor site, performance status, size, primary versus recurrence, and radiation dose. A comparison to a conventionally treated patient group did not show a significant survival improvement. 3 months after treatment, initial symptoms had improved in 59% (hemiparesis), 50% (aphasia), 50% (hemianopsia), and 60% (convulsions). IORT has been shown to be feasible; perioperative complication rates were not increased. Survival was generally not improved compared to a historical control group. Recurrences achieved the same survival as primary tumors, and GBM also had a slightly increased survival, thus being possible indications for IORT.

Therapeutic Effects of Stereotactic Radiotherapy on 389 Cases of Brain Glioma

Objective: To investigate the treatment effectiveness and side effects of stereotactic radiotherapy for brain glioma. Methods: From Jun. 1995 to Dec. 1998, 389 cases of brain gliomas were treated by stereotactic radiotherapy, among which 151 cases were treated by stereotactic radiosurgery (SRS) and the other 238 cases, by fractionated stereotactic radiotherapy (FSRT). In the SRS group, the marginal tumor dose was 20 to 30 Gy (median, 2.6 Gy). One to 6 isocenters (median, 2.48) and 5 to 21 irradiation arcs (median, 8.45) were applied. In the FSRT group, the per-fraction marginal tumor dose was 8 to 12 Gy with 1 to 6 isocenters (median, 2.53), 6 to 20 irradiation arcs (median, 8.25) and 2-5 fractions delivered everyday or every other day. Results: Three months after treatment, the complete and partial response rates were 13.9% and 45.7% in SRS group respectively. The stable disease rate was 17.2%. The total effective rate was 76.8%. In FSRT group, the complete and partial remission rates were 19.7% and 47.9% respectively. The stable disease rate was 20.6%. The total effective rate was 88.2%. The total effective rate of FSRT group was higher than that in SRS group (χ2=9.874, P=0.020). The 1-year, 3-year and 5-year survival rate of all patients was 54.3%, 29.3%, 16.5% respectively. The 1-year, 3-year and 5-year survival rate in SRS group and FSRT group was 52.3% vs 26.5%, 11.9% vs 55.5%, and 31.1 vs 19.3% respectively. There was no significant difference between the two groups (χ2=2.16, P=0.1417). The brain edema caused by the main radiation was more severe in the SRS group than in FSRT group (χ2=4.916, P=0.027). Conclusion: It is effective for brain glioma to be treated by stereotactic radiotherapy. Compared with SRS, the FSRT has the advantage of good effect and less side response.

Use of Magnetic Resonance Imaging to Assess Blood-Brain/Blood-Glioma Barrier Opening During Conformal Radiotherapy

For chemotherapy to act synergistically and safely with radiation against high-grade gliomas, drugs must pass the endothelial junctions of the blood-tumor barrier (BTB) to reach all tumor cells, and should not pass the blood-brain barrier (BBB) to cause toxicity to normal brain. The objective of this study was to assess BBB/BTB status using magnetic resonance imaging (MRI) during a course of radiotherapy of high-grade gliomas. Sixteen patients with grade 3 or 4 supratentorial malignant glioma receiving conformal radiotherapy (RT) underwent contrast-enhanced MRI before, during, and after completion of RT. A gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) uptake index was analyzed with respect to the tumor and RT dose received. In the nonenhanced tumor region, contrast uptake increased significantly after the receipt of approximately 10 Gy (P < .01), and reached a maximum after the receipt of approximately 30 Gy. In the initially contrast-enhanced tumor region, contrast uptake decreased over the course of RT and became significant after completion of RT in patients without progressive disease. The healthy brain showed only nonsignificant changes during and after irradiation. Contrast MRI reveals increases in Gd-DTPA uptake in the initially nonenhanced tumor region but not in the remaining brain during the course of RT, suggesting opening of the BTB. This finding suggests that the effect of conformal radiation is more selective on the BTB than the BBB, and there may be a window extending from 1 week after the initiation of radiotherapy to 1 month after the completion of treatment during which a pharmaceutical agent has maximum access to high-grade gliomas.

SU-FF-T-382: Planning Non-Uniform Dose Distributions for Brain Tumor

Purpose: Inhomogeneous radiobiology exists within tumor volume of malignant gliomas as shown by biological imaging. The purpose of this project is to plan non-uniform dose distributions to account for inhomogeneous radiosensitivity using IMRT. Method and Materials: Sample tumor volumes were divided into several sub-regions of different radiosensitivity that may be considered to correspond to different tumor grade. A pooled clinical and in-vitro data for gliomas were analyzed to determine radiosensitivity parameters for different tumor grades. LQ model and equivalent uniform dose (EUD) were used to calculate the required radiation dose to account for different tumor grade in different sub-region. While the required dose in each sub-region is uniform, the dose distribution within the entire tumor volume is non-uniform. The Xio/CMS IMRT planning system was used to plan the required non-uniform dose distributions and also the conventional 60Gy uniform dose. The EUDs for both uniform and non-uniform distributions were compared. Results: Using the parameters determined from clinical data the required dose (EUD in 2Gy fractions) was found to be >55Gy for grade 1 or 2, >60Gy for grade 3 and >65Gy for grade 4. Considering low tumor grade (thus low dose) existing in periphery region, IMRT can deliver the required non-uniform distributions while keeping or improving normal-tissue sparing compared to the conventional uniform dose delivery. The dose can be escalated even higher than the required value in a high-grade region. The non-uniform dose plans yield higher tumor EUD and lower or the same normal-tissue EUD as compared to the conventional plan, indicating that the non-uniform doses are more effective. Conclusion: It is dosimetrically feasible to plan non-uniform dose distributions to account for inhomogeneous radiosensitivity. This prepares a framework for biological imaging guided radiotherapy of malignant gliomas, a leading cause of cancer mortality in people with young ages.

Target delineation in post-operative radiotherapy of brain gliomas: Interobserver variability and impact of image registration of MR(pre-operative) images on treatment planning CT scans

Background and purposeTo investigate the interobserver variability of intracranial tumour delineation on computed tomography (CT) scans using pre-operative MR hardcopies (CT+MR(conv)) or CT-MR (pre-operative) registered images (CT+MR(matched)). Patients and methodsFive physicians outlined the ‘initial’ clinical tumour volume (CTV0) of seven patients affected by HGG and candidates for radiotherapy (RT) after radical resection. The observers performed on screen-tumour delineation using post-operative CT images of the patients in the treatment position and pre-operative MR radiographs (CT+MR(conv)); they also outlined CTV0 with both CT and corresponding MR axial image on screen (CT+MR(matched)). The accuracy of the image fusion was quantitatively assessed. An analysis was conducted to assess the variability among the five observers in CT+MR(conv) and CT+MR(matched) modality. ResultsThe registration accuracy in 3D space is always less than 3.7mm. The concordance index was significantly better in CT+MR(matched) (47.4±12.4%) than in CT+MR(conv) (14.1±12.7%) modality (P<0.02). The intersecting volumes represent 67±15 and 24±18% of the patient mean volume for CT+MR(matched) and CT+MR(conv), respectively (P<0.02). ConclusionsThe use of CT and MR registered imaging reduces interobserver variability in target volume delineation for post-operative irradiation of HGG; smaller margins around target volume could be adopted in defining irradiation technique.

139 Image fusion guided 125 iodine interstitial irradiation of gliomas

139 Image fusion guided 125 iodine interstitial irradiation of gliomas

Successful combination of local CpG‐ODN and radiotherapy in malignant glioma

Oligodeoxynucleotides containing CpG motifs (CpG-ODN) display broad immunostimulating activity and are currently under clinical trial in various malignancies, including recurrent glioblastomas. Combining CpG-ODN with another therapy that could induce antigen release might enhance tumor-specific immune response. We investigated whether radiotherapy (RT) could be associated advantageously to intratumoral injections of CpG-ODN. Fisher rats bearing 9L glioma were treated with various combinations of RT and CpG-28, an oligonucleotide with good immunostimulating activity. RT and CpG-28 induced complete tumor remission in one-third of the animals. When both treatments were combined, complete tumor remission was achieved in two-thirds of the animals (p < 0.001 when compared to non-treated rats, p < 0.03 when compared to CpG-28 alone). Such efficacy was not observed in nude mice, underlying the role of T cells in antitumor effects. The combination of both treatments appeared optimal when the delay between RT and CpG-28 administration was <3 days (from 100% survival for a 3 days delay, to 57% survival for a 21 days delay, p < 0.05). Tumor infiltration by immune cells and expression within tumors of the CpG receptor, TLR9, were not modified by irradiation. These results support an attractive strategy of sequential radiotherapy and immunotherapy by CpG-ODN and have potential implications for future clinical trials with CpG-ODN.

Prognosis of gliomas in the 1970s and today

The benefit of the current strategy for diagnosis (magnetic resonance, [MR] imaging) and treatment (surgery, chemotherapy, radiotherapy) of gliomas, in contrast to the standard treatment in use before MR imaging and the microsurgical era, has not yet been determined. A retrospective statistical analysis was performed for all patients with glioma who underwent surgery at a single institution between 1965 and 1974 (Group I, 88 patients) or 1986 and 1995 (Group II, 249 patients). There were no major differences in symptomatology, tumor localization, and number of surgical procedures. The mean time until tumor diagnosis was significantly shorter in Group II (Group I, 48 weeks; Group II, 19.5 weeks). Also, the mean time from initial symptoms to surgery was significantly shorter for high-grade gliomas in Group II (Group I, 16.3 weeks; Group II, 11.7 weeks). For high- as well as low-grade gliomas, there was a clear reduction of the perioperative morbidity and mortality rates in Group II. Nevertheless, for the postoperative duration of survival, no significant differences were demonstrated for high- or low-grade gliomas. Based on the results of this study, the perioperative morbidity and mortality rate as well as the time from diagnosis to treatment have been remarkably reduced within the last 30 years. Nevertheless, the overall prognosis for patients with gliomas has not changed from the 1970s until today. Thus, the introduction of modern diagnostic modalities and surgical procedures has not improved the outcome in patients with glioma. Further research to improve the treatment of this disease is urgently needed.

Evaluating changes in tumor volume using magnetic resonance imaging during the course of radiotherapy treatment of high-grade gliomas: Implications for conformal dose-escalation studies

To determine whether changes in tumor volume occur during the course of conformal 3D radiotherapy of high-grade gliomas by use of magnetic resonance imaging (MRI) during treatment and whether these changes had an impact on tumor coverage. Between December 2000 and January 2004, 21 patients with WHO Grades 3 to 4 supratentorial malignant gliomas treated with 3D conformal radiotherapy (median dose, 70 Gy) were enrolled in a prospective clinical study. All patients underwent T1-weighted contrast-enhancing and T2-weighted and fluid-attenuated inversion recovery (FLAIR) imaging at approximately 1 to 2 weeks before radiotherapy, during radiotherapy (Weeks 1 and 3), and at routine intervals thereafter. All MRI scans were coregistered to the treatment-planning CT. Gross tumor volume (GTV Pre-Rx) was defined from a postoperative T1-weighted contrast-enhancing MRI performed 1 to 2 weeks before start of radiotherapy. A second GTV (GTV Week 3) was defined by use of an MRI performed during Week 3 of radiotherapy. A uniform 0.5 cm expansion of the respective GTV, PTV (Pre-Rx), and PTV (Week 3) was applied to the final boost plan. Dose-volume histograms (DVH) were used to analyze any potential adverse changes in tumor coverage based on Week 3 MRI. All MRI scans were reviewed independently by a neuroradiologist (DGH). Two patients were noted to have multifocal disease at presentation and were excluded from analysis. In 19 cases, changes in the GTV based on MRI at Week 3 during radiotherapy were as follows: 2 cases had an objective decrease in GTV (> or =50%); 12 cases revealed a slight decrease in the rim enhancement or changes in cystic appearance of the GTV; 2 cases showed no change in GTV; and 3 cases demonstrated an increase in tumor volume. Both cases with objective decreases in GTV during treatment were Grade 3 tumors. No cases of tumor progression were noted in Grade 3 tumors during treatment. In comparison, three of 12 Grade 4 tumors had tumor progression, based on MRI obtained during Week 3 of radiotherapy. Median increase in GTV (Week 3) was 11.7 cc (range, 9.8-21.3). Retrospective DVH analysis of PTV (Pre-Rx) and PTV (Week 3) demonstrated a decrease in V(95%)(PTV volume receiving 95% of the prescribed dose) in those 3 cases. Routine MR imaging during radiotherapy may be essential in ensuring tumor coverage if highly conformal radiotherapy techniques such as stereotactic boost and intensity-modulated radiotherapy are used in dose-escalation trials that utilize smaller treatment margins.

Neoadjuvant cisplatin and etoposide, with or without tamoxifen, prior to radiotherapy in high-grade gliomas: a single-center experience

Neoadjuvant chemotherapy (CT), prior to radical radiotherapy (RT), in the treatment of high-grade gliomas may offer several advantages over standard adjuvant CT. The addition of tamoxifen, which can circumvent P-glycoprotein (P-gp)-mediated chemo-resistance, also merits attention. We have evaluated the neoadjuvant regimen of cisplatin and etoposide after surgery of grade III-IV gliomas and prior to radical RT, with regard to response rates (RRs), overall survival (OS) and time to progression (TTP). The synergistic activity between etoposide and tamoxifen was also studied. Forty-four patients were included. CT regime: cisplatin 100 mg/m2 on day +1 and etoposide 100 mg/m2 on days +1 to +3 every 3 weeks for 3 cycles. The initial 24 were also treated with high-dose tamoxifen, 275 mg/m2 on days -3 to +3. An immunohistochemical analysis of P-gp, p53, vascular endothelial growth factor, Ki67 and bcl-2 was also performed. Median follow-up was 11.57 months. In the 16 patients with measurable disease after surgery, a RR of 12.5% was seen, with 37.5% of disease stabilizations and 31.25% of progressions. The median OS and TTP were 11.3 and 5.7 months. Excluding the three deaths possibly related to tamoxifen, grade 3-4 was low, mainly emesis. Favorable prognostic factors were age less than 60 years, extent of surgery, absence of measurable disease, and the absence of radiological necrosis and ring enhancement. Only high p53 expression was associated with better OS. We conclude that neoadjuvant cisplatin and etoposide is a feasible regime, although any real advantage over standard adjuvant CT is dubious. Short-course high-dose tamoxifen should not be used alongside primary CT.

Efficacy and Toxicity of Postoperative Temozolomide Radiochemotherapy in Malignant Glioma

To evaluate the feasibility, safety and efficacy of daily temozolomide concurrent with postoperative radiotherapy in malignant glioma. From 11/1999 to 03/2003, n = 81 patients aged 15-72 years (median 52 years, Karnofsky score 80-100% in 83%) suffering from primary glioblastoma (n = 47), anaplastic astrocytoma (n = 6), anaplastic oligodendroglioma (n = 16), and recurrent glioma (n = 12) were treated. Patients with primary gliomas received a combination of postoperative radiotherapy (60 Gy/1.8- to 2.0-Gy fractions) and daily oral temozolomide (75 mg/m(2)) at all irradiation days (30-33 doses), while recurrent tumors were treated with 45-60 Gy and temozolomide. Initially, 6/81 patients had daily temozolomide doses of 50 mg/m(2). In total, 70/81 patients (86%) completed both radio- and chemotherapy. Grade 1 nausea/vomiting was seen in 28%, grade 2 in 11%, grade 3 in 1%. Antiemetics were applied in 41%. Hematologic toxicities were observed as follows: leukopenia grade 3/4 1%, lymphopenia grade 3/4 46%, thrombopenia grade 3/4 1%. Two patients under dexamethasone suffered herpes encephalitis after one and 16 doses of temozolomide (75 mg/m(2)). Median survival was 15 months for glioblastoma. In oligodendroglioma patients, a 4-year survival rate of 78% was observed. Postoperative radiochemotherapy with 30-33 daily doses of temozolomide (75 mg/m(2)) is safe in patients with malignant glioma. The combined schedule is effective in oligodendroglioma patients and may prolong survival in glioblastoma. Effort should be taken to minimize corticosteroid doses, since both steroids and temozolomide lead to immunosuppression.

悪性グリオーマに対する放射線治療 : 治療最前線

悪性グリオーマに対する放射線治療は, 50&acd;60Gyの外部照射が一般的であるが, これまでの報告では, 生存期間中央値(median survival time ; MST)は12&acd;14カ月程度であった.照射線量を70&acd;80Gyまで上げるために, 1日に2&acd;3回の照射を行う多分割照射が行われたが, その治療成績は通常外照射に勝っていない.悪性グリオーマの治癒を目指して近年, 種々の放射線治療が行われている.ガンマナイフ, リニアック, サイバーナイフの定位的放射線照射は, 外照射と組み合わせて行い, 局所コントロールの改善が報告されている.一方, 粒子線治療は, 高LET放射線であり, 腫瘍細胞を直接に傷害することで治癒が期待される.本邦では, 粒子線治療として, 炭素イオンを用いる重粒子線治療と, 中性子と硼素化合物を用いる中性子捕捉療法(boron neutron capture therapy ; BNCT)が世界に先駆けて臨床試験が行われている.本稿では, 悪性グリオーマに対する放射線治療の治療成績について, 過去に行われたエビデンスレベルの高い報告を紹介し, 標準的放射線治療について現状を述べる.また, 粒子線治療については臨床治験の治療成績を報告する.