Neon heavy charged particle radiotherapy of glioblastoma of the brain

Treatment of newly diagnosed glioblastoma in the elderly: a network meta-analysis

BACKGROUND

A glioblastoma is a fatal type of brain tumour for which the standard of care is maximum surgical resection followed by chemoradiotherapy, when possible. Age is an important consideration in this disease, as older age is associated with shorter survival and a higher risk of treatment-related toxicity.

OBJECTIVES

To determine the most effective and best-tolerated approaches for the treatment of elderly people with newly diagnosed glioblastoma. To summarise current evidence for the incremental resource use, utilities, costs and cost-effectiveness associated with these approaches.

SEARCH METHODS

We searched electronic databases including the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and Embase to 3 April 2019, and the NHS Economic Evaluation Database (EED) up to database closure. We handsearched clinical trial registries and selected neuro-oncology society conference proceedings from the past five years.

SELECTION CRITERIA

Randomised trials (RCTs) of treatments for glioblastoma in elderly people. We defined 'elderly' as 70+ years but included studies defining 'elderly' as over 65+ years if so reported.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods for study selection and data extraction. Where sufficient data were available, treatment options were compared in a network meta-analysis (NMA) using Stata software (version 15.1). For outcomes with insufficient data for NMA, pairwise meta-analysis were conducted in RevMan. The GRADE approach was used to grade the evidence.

MAIN RESULTS

We included 12 RCTs involving approximately 1818 participants. Six were conducted exclusively among elderly people (either defined as 65 years or older or 70 years or older) with newly diagnosed glioblastoma, the other six reported data for an elderly subgroup among a broader age range of participants. Most participants were capable of self-care. Study quality was commonly undermined by lack of outcome assessor blinding and attrition. NMA was only possible for overall survival; other analyses were pair-wise meta-analyses or narrative syntheses. Seven trials contributed to the NMA for overall survival, with interventions including supportive care only (one trial arm); hypofractionated radiotherapy (RT40; four trial arms); standard radiotherapy (RT60; five trial arms); temozolomide (TMZ; three trial arms); chemoradiotherapy (CRT; three trial arms); bevacizumab with chemoradiotherapy (BEV_CRT; one trial arm); and bevacizumab with radiotherapy (BEV_RT). Compared with supportive care only, NMA evidence suggested that all treatments apart from BEV_RT prolonged survival to some extent. Overall survival High-certainty evidence shows that CRT prolongs overall survival (OS) compared with RT40 (hazard ratio (HR) 0.67, 95% confidence interval (CI) 0.56 to 0.80) and low-certainty evidence suggests that CRT may prolong overall survival compared with TMZ (TMZ versus CRT: HR 1.42, 95% CI 1.01 to 1.98). Low-certainty evidence also suggests that adding BEV to CRT may make little or no difference (BEV_CRT versus CRT: HR 0.83, 95% CrI 0.48 to 1.44). We could not compare the survival effects of CRT with different radiotherapy fractionation schedules (60 Gy/30 fractions and 40 Gy/15 fractions) due to a lack of data. When treatments were ranked according to their effects on OS, CRT ranked higher than TMZ, RT and supportive care only, with the latter ranked last. BEV plus RT was the only treatment for which there was no clear benefit in OS over supportive care only.   One trial comparing tumour treating fields (TTF) plus adjuvant chemotherapy (TTF_AC) with adjuvant chemotherapy alone could not be included in the NMA as participants were randomised after receiving concomitant chemoradiotherapy, not before. Findings from the trial suggest that the intervention probably improves overall survival in this selected patient population. We were unable to perform NMA for other outcomes due to insufficient data. Pairwise analyses were conducted for the following. Quality of life Moderate-certainty narrative evidence suggests that overall, there may be little difference in QoL between TMZ and RT, except for discomfort from communication deficits, which are probably more common with RT (1 study, 306 participants, P = 0.002). Data on QoL for other comparisons were sparse, partly due to high dropout rates, and the certainty of the evidence tended to be low or very low. Progression-free survival High-certainty evidence shows that CRT increases time to disease progression compared with RT40 (HR 0.50, 95% CI 0.41 to 0.61); moderate-certainty evidence suggests that RT60 probably increases time to disease progression compared with supportive care only (HR 0.28, 95% CI 0.17 to 0.46), and that BEV_RT probably increases time to disease progression compared with RT40 alone (HR 0.46, 95% CI 0.27 to 0.78). Evidence for other treatment comparisons was of low- or very low-certainty. Severe adverse events Moderate-certainty evidence suggests that TMZ probably increases the risk of grade 3+ thromboembolic events compared with RT60 (risk ratio (RR) 2.74, 95% CI 1.26 to 5.94; participants = 373; studies = 1) and also the risk of grade 3+ neutropenia, lymphopenia, and thrombocytopenia. Moderate-certainty evidence also suggests that CRT probably increases the risk of grade 3+ neutropenia, leucopenia and thrombocytopenia compared with hypofractionated RT alone. Adding BEV to CRT probably increases the risk of thromboembolism (RR 16.63, 95% CI 1.00 to 275.42; moderate-certainty evidence). Economic evidence There is a paucity of economic evidence regarding the management of newly diagnosed glioblastoma in the elderly. Only one economic evaluation on two short course radiotherapy regimen (25 Gy versus 40 Gy) was identified and its findings were considered unreliable.

AUTHORS' CONCLUSIONS

For elderly people with glioblastoma who are self-caring, evidence suggests that CRT prolongs survival compared with RT and may prolong overall survival compared with TMZ alone. For those undergoing RT or TMZ therapy, there is probably little difference in QoL overall. Systemic anti-cancer treatments TMZ and BEV carry a higher risk of severe haematological and thromboembolic events and CRT is probably associated with a higher risk of these events. Current evidence provides little justification for using BEV in elderly patients outside a clinical trial setting. Whilst the novel TTF device appears promising, evidence on QoL and tolerability is needed in an elderly population. QoL and economic assessments of CRT versus TMZ and RT are needed. More high-quality economic evaluations are needed, in which a broader scope of costs (both direct and indirect) and outcomes should be included.

Physical advantages of particles: protons and light ions

Proton and ion beam therapy has been introduced in the Lawrence Berkeley National Laboratory in the mid-1950s, when protons and helium ions have been used for the first time to treat patients. Starting in 1972, the scientists at Berkeley also were the first to use heavier ions (carbon, oxygen, neon, silicon and argon ions). The first clinical ion beam facility opened in 1994 in Japan and since then, the interest in radiotherapy with light ion beams has been increasing slowly but steadily, with 13 centers in clinical operation in 2019. All these centers are using carbon ions for clinical application.The article outlines the differences in physical properties of various light ions as compared to protons in view of the application in radiotherapy. These include the energy loss and depth dose properties, multiple scattering, range straggling and nuclear fragmentation. In addition, the paper discusses differences arising from energy loss and linear energy transfer with respect to their biological effects.Moreover, the paper reviews briefly the existing clinical data comparing protons and ions and outlines the future perspectives for the clinical use of ions like oxygen and helium.

The radiobiological effects of He, C and Ne ions as a function of LET on various glioblastoma cell lines

The effects of the charged ion species 4He, 12C and 20Ne on glioblastoma multiforme (GBM) T98G, U87 and LN18 cell lines were compared with the effects of 200 kVp X-rays (1.7 keV/μm). These cell lines have different genetic profiles. Individual GBM relative biological effectiveness (RBE) was estimated in two ways: the RBE10 at 10% survival fraction and the RBE2Gy after 2 Gy doses. The linear quadratic model radiosensitivity parameters α and β and the α/β ratio of each ion type were determined as a function of LET. Mono-energetic 4He, 12C and 20Ne ions were generated by the Heavy Ion Medical Accelerator at the National Institute of Radiological Sciences in Chiba, Japan. Colony-formation assays were used to evaluate the survival fractions. The LET of the various ions used ranged from 2.3 to 100 keV/μm (covering the depth-dose plateau region to clinically relevant LET at the Bragg peak). For U87 and LN18, the RBE10 increased with LET and peaked at 85 keV/μm, whereas T98G peaked at 100 keV/μm. All three GBM α parameters peaked at 100 keV/μm. There is a statistically significant difference between the three GBM RBE10 values, except at 100 keV/μm (P < 0.01), and a statistically significant difference between the α values of the GBM cell lines, except at 85 and 100 keV/μm. The biological response varied depending on the GBM cell lines and on the ions used.

Survival in glioblastoma: a review on the impact of treatment modalities

Glioblastoma (GBM) is the most common and lethal tumor of the central nervous system. The natural history of treated GBM remains very poor with 5-year survival rates of 5 %. Survival has not significantly improved over the last decades. Currently, the best that can be offered is a modest 14-month overall median survival in patients undergoing maximum safe resection plus adjuvant chemoradiotherapy. Prognostic factors involved in survival include age, performance status, grade, specific markers (MGMT methylation, mutation of IDH1, IDH2 or TERT, 1p19q codeletion, overexpression of EGFR, etc.) and, likely, the extent of resection. Certain adjuncts to surgery, especially cortical mapping and 5-ALA fluorescence, favor higher rates of gross total resection with apparent positive impact on survival. Recurrent tumors can be offered re-intervention, participation in clinical trials, anti-angiogenic agent or local electric field therapy, without an evident impact on survival. Molecular-targeted therapies, immunotherapy and gene therapy are promising tools currently under research.

Enhancing radiation therapy for patients with glioblastoma

Radiation therapy has been the foundation of therapy following maximal surgical resection in patients with newly diagnosed glioblastoma for decades and the primary therapy for unresected tumors. Using the standard approach with radiation and temozolomide, however, outcomes are poor, and glioblastoma remains an incurable disease with the majority of recurrences and progression within the radiation treatment field. As such, there is much interest in elucidating the mechanisms of resistance to radiation therapy and in developing novel approaches to overcoming this treatment resistance.

Rationale for carbon ion therapy in high-grade glioma based on a review and a meta-analysis of neutron beam trials

PURPOSE

The standard treatment of high-grade glioma is still unsatisfactory: the 2-year survival after radiotherapy being only 10-25%. A high linear energy transfer (LET) ionising radiotherapy has been used to overcome tumour radioresistance. An overview of the field is needed to justify future prospective controlled studies on carbon ion therapy.

MATERIALS AND METHODS

A meta-analysis of clinical trials on neutron beam therapy and a literature review of clinical investigations on light ion use in high-grade glioma were carried out.

RESULTS

Four randomised controlled trials on neutron beam therapy were retained. The meta-analysis showed a non-significant 6% increase of two-year mortality (Relative risk [RR]=1.06 [0.97-1.15]) in comparison with photon therapy. Two phase I/II trials on carbon and neon ion therapy reported for glioblastoma 10% and 31% two-year overall survivals and 13.9 and 19.0 months median survivals, respectively.

CONCLUSION

This meta-analysis suggests that neutron beam therapy does not improve the survival of high-grade glioma patients while there is no definitive conclusion yet regarding carbon therapy. The ballistic accuracy and the improved biological efficacy of carbon ions renew the interest in prospective clinical trials on particle beam radiotherapy of glioma and let us expect favourable effects of dose escalation on patients' survival.

The potential of proton beam radiation therapy in intracranial and ocular tumours

A group of oncologists and hospital physicists have estimated the number of patients in Sweden suitable for proton beam therapy. The estimations have been based on current statistics of tumour incidence, number of patients potentially eligible for radiation treatment, scientific support from clinical trials and model dose planning studies and knowledge of the dose-response relations of different tumours and normal tissues. In intracranial benign and malignant tumours, it is estimated that between 130 and 180 patients each year are candidates for proton beam therapy. Of these, between 50 and 75 patients have malignant glioma, 30-40 meningeoma, 20-25 arteriovenous malformations, 20-25 skull base tumours and 10-15 pituitary adenoma. In addition, 15 patients with ocular melanoma are candidates.

Induction of cytogenetic adaptive response in spermatogonia and spermatocytes by pre-exposure of mouse testis to low-dose (12)C(6+) ions

To investigate the effects of pre-exposure of mouse testis to low-dose (12)C(6+) ions on cytogenetics of spermatogonia and spermatocytes induced by subsequent high-dose irradiation, the testes of outbred Kun-Ming strain mice were irradiated with 0.05Gy of (12)C(6+) ions as the pre-exposure dose, and then irradiated with 2Gy as challenging dose at 4h after per-exposure. Poly(ADP-ribose) polymerase (PARPs) activity and PARP-1 protein expression were respectively measured by using the enzymatic and Western blot assays at 4h after irradiation; chromosomal aberrations in spermatogonia and spermatocytes were analyzed by the air-drying method at 8h after irradiation. The results showed that there was a significant increase in the frequency of chromosomal aberrations and significant reductions of PARP activity and PARP-1 expression level in the mouse testes irradiated with 2Gy of (12)C(6+) ions. However, pre-exposure of mouse testes to a low dose of (12)C(6+) ions significantly increased PARPs activity and PARP-1 expression and alleviated the harmful effects induced by a subsequent high-dose irradiation. PARP activity inhibitor 3-aminobenzamide (3-AB) treatment blocked the effects of PARP-1 on cytogenetic adaptive response induced by low-dose (12)C(6+) ion irradiation. The data suggest that pre-exposure of testes to a low dose of heavy ions can induce cytogenetic adaptive response to subsequent high-dose irradiation. The increase of PARP-1 protein induced by the low-dose ionizing irradiation may be involved in the mechanism of these observations.

Chained Lightning, Part I

The fundamental principle of radiosurgery is the focusing of energy within a restricted target volume. In examining the history of radiosurgery, various strategies for addressing this issue of energy containment become apparent. This is the first in a series of articles that reviews the evolution of radiosurgery through the development of instruments for beam generation and delivery for improved conformal therapy.

In this first part of the series, we focus specifically on beam generation and the development of particle beams as the initial approach in radiosurgery for focused radiation treatment. We examine the physical characteristics and biological effects of particles and the unique advantage they confer for radiosurgery. We consider clinical studies and treatment of neurological diseases with particles and also assess boron neutron capture therapy as a strategy for selectively targeting neutron beams.

Later in this series, we explore methods of beam delivery with the development of stereotactic radiosurgery. Finally, we introduce new concepts and applications in radiosurgery such as nanotechnology, radiation enhancement, ultrasound, near infrared, and free electron lasers.

The elaboration of these efforts sets the stage for neurosurgeons to further explore new ideas, develop innovative technology, and advance the practice of radiosurgery.

Phase I/II clinical trial of carbon ion radiotherapy for malignant gliomas: combined X-ray radiotherapy, chemotherapy, and carbon ion radiotherapy

PURPOSE

To report the results of a Phase I/II clinical trial for patients with malignant gliomas, treated with combined X-ray radiotherapy (XRT), chemotherapy, and carbon ion radiotherapy (CRT).

METHODS AND MATERIALS

Between October 1994 and February 2002, 48 patients with histologically confirmed malignant gliomas (16 anaplastic astrocytoma (AA) and 32 glioblastoma multiforme (GBM) were enrolled in a Phase I/II clinical study. The treatment involved the application of 50 Gy/25 fractions/5 weeks of XRT, followed by CRT at 8 fractions/2 weeks. Nimustine hydrochloride (ACNU) were administered at a dose of 100 mg/m(2) concurrently in weeks 1, 4, or 5 of XRT. The carbon ion dose was increased from 16.8 to 24.8 Gray equivalent (GyE) in 10% incremental steps (16.8, 18.4, 20.0, 22.4, and 24.8 GyE, respectively).

RESULTS

There was no Grade 3 or higher acute reaction in the brain. The late reactions included four cases of Grade 2 brain morbidity and four cases of Grade 2 brain reaction among 48 cases. The median survival time (MST) of AA patients was 35 months and that of GBM patients 17 months (p = 0.0035). The median progression-free survival and MST of GBM showed 4 and 7 months for the low-dose group, 7 and 19 months for the middle-dose group, and 14 and 26 months for the high-dose group.

CONCLUSION

The results of combined therapy using XRT, ACNU chemotherapy, and CRT showed the potential efficacy of CRT for malignant gliomas in terms of the improved survival rate in those patients who received higher carbon doses.

Alleviation of pre-exposure of mouse brain with low-dose12C6+ion or60Co gamma-ray on male reproductive endocrine damages induced by subsequent high-dose irradiation

Irradiation has been widely reported to damage organisms by attacking on proteins, nucleic acid and lipids in cells. However, radiation hormesis after low-dose irradiation has become the focus of research in radiobiology in recent years. To investigate the effects of pre-exposure of mouse brain with low-dose (12)C6+ ion or 60Co gamma (gamma)-ray on male reproductive endocrine capacity induced by subsequent high-dose irradiation, the brains of the B6C3F1 hybrid strain male mice were irradiated with 0.05 Gy of (12)C6+ ion or 60Co gamma-ray as the pre-exposure dose, and were then irradiated with 2 Gy as challenging irradiation dose at 4 h after pre-exposure. Serum pituitary gonadotropin hormones, follicle-stimulating hormone (FSH) and luteinizing hormone (LH), testosterone, testis weight, sperm count and shape were measured on the 35th day after irradiation. The results showed that there was a significant reduction in the levels of serum FSH, LH, testosterone, testis weight and sperm count, and a significant increase in sperm abnormalities by irradiation of the mouse brain with 2 Gy of (12)C6+ ion or 60Co gamma-ray. Moreover, the effects were more obvious in the group irradiated by (12)C6+ ion than in that irradiated by 60Co gamma-ray. Pre-exposure with low-dose (12)C6+ ion or 60Co gamma-ray significantly alleviated the harmful effects induced by a subsequent high-dose irradiation.

[Malignant gliomas--radiotherapy]

Postoperative radiotherapy is the treatment of choice for high grade gliomas and glioblastomas. The goal of the adjuvant radiotherapy is to improve local control and long term survival. The benefit of re-irradiation for recurrent or progressive glioma is controversial. The therapeutic benefit of any radiotherapy intervention must be balanced by the risk of neurotoxicity and its impact on quality of life.

Clinical and research validity of hadrontherapy with ion beams

Clinical results obtained with hadrontherapy have been extremely positive for various tumours, with percentages of local control and survival higher than those ascribed to conventional radiotherapy. Most clinical data obtained with charged particles are related to protontherapy but the implementation of carbon ion therapy has demonstrated to be of great interest in the last decade. These results, accompanied by the new performances in accelerator technology and calculation systems of the delivered doses, have determined over the past years an increased interest for the development of hadrontherapy, with the construction of new centres provided with equipment entirely dedicated to clinical activity (LLUMC, Loma Linda and NPTC, Boston in USA, HIMAC-NIRS, Chiba, PROBEAT, Tsukuba, and Hyogo Beam Medical Centres in Japan). A revision of the clinical indications specifically focused on ion therapy is presented as well as the results obtained in the different centres. With hadrontherapy, it is finally possible to increase the spectrum of treatments allowing preserving the organ and its functionality, with positive impacts from a social and economic point of view.

Late effects from hadron therapy

Successful cancer patient survival and local tumor control from hadron radiotherapy warrant a discussion of potential secondary late effects from the radiation. The study of late-appearing clinical effects from particle beams of protons, carbon, or heavier ions is a relatively new field with few data. However, new clinical information is available from pioneer hadron radiotherapy programs in the USA, Japan, Germany and Switzerland. This paper will review available data on late tissue effects from particle radiation exposures, and discuss its importance to the future of hadron therapy. Potential late radiation effects are associated with irradiated normal tissue volumes at risk that in many cases can be reduced with hadron therapy. However, normal tissues present within hadron treatment volumes can demonstrate enhanced responses compared to conventional modes of therapy. Late endpoints of concern include induction of secondary cancers, cataract, fibrosis, neurodegeneration, vascular damage, and immunological, endocrine and hereditary effects. Low-dose tissue effects at tumor margins need further study, and there is need for more acute molecular studies underlying late effects of hadron therapy.

Common challenges and problems in clinical trials of boron neutron capture therapy of brain tumors

Clinical trials for binary therapies, like boron neutron capture therapy (BNCT), pose a number of unique problems and challenges in design, performance, and interpretation of results. In neutron beam development, different groups use different optimization parameters, resulting in beams being considerably different from each other. The design, development, testing, execution of patient pharmacokinetics and the evaluation of results from these studies differ widely. Finally, the clinical trials involving patient treatments vary in many aspects such as their dose escalation strategies, treatment planning methodologies, and the reporting of data. The implications of these differences in the data accrued from these trials are discussed. The BNCT community needs to standardize each aspect of the design, implementation, and reporting of clinical trials so that the data can be used meaningfully.

Clinical review of the Japanese experience with boron neutron capture therapy and a proposed strategy using epithermal neutron beams

Our concept of boron neutron capture therapy (BNCT) is selective destruction of tumor cells using the heavy-charged particles yielded through 10B(n, alpha)7 Li reactions. To design a new protocol that employs epithermal neutron beams in the treatment of glioma patients, we examined the relationship between the radiation dose, histological tumor grade, and clinical outcome. Since 1968, 183 patients with different kinds of brain tumors were treated by BNCT; for this retrospective study, we selected 105 patients with glial tumors who were treated in Japan between 1978 and 1997. In the analysis of side effects due to radiation, we included all the 159 patients treated between 1977 and 2001. With respect to the radiation dose (i.e. physical dose of boron n-alpha reaction), the new protocol prescribes a minimum tumor volume dose of 15 Gy or, alternatively, a minimum target volume dose of 18 Gy. The maximum vascular dose should not exceed 15 Gy (physical dose of boron n-alpha reaction) and the total amount of gamma rays should remain below 10 Gy, including core gamma rays from the reactor and capture gamma in brain tissue. The outcomes for 10 patients who were treated by the new protocol using a new mode composed of thermal and epithermal neutrons are reported.

[The French project ETOILE: review of clinical data for light ion hadrontherapy]

The Lawrence Berkeley Laboratory was the pioneer in light ions hadrontherapy with almost 2500 patients treated between 1957 and 1993 with Helium and Neon. The NIRS (National Institute For Radiological Science, Chiba, Japan) was the first dedicated medical centre for cancer with more than 1200 patients exclusively treated with carbon ion from 1994. A three-year 70 to 100% local control was reported for radio-resistant cancers, supporting the use of high LET particles. Hypo-fractionation was particularly explored for lung cancers and hepatocarcinoma (4 sessions only). Dose escalation studies demonstrated a tumour dose-effect and permitted to precise dose constraints for healthy tissues especially for the rectum. More than 140 patients were treated with carbon ion exclusively or associated with photons since 1997 in the GSI laboratory Gesellschaft Für Schwerionenforschung, Darmstadt, Germany). A very high local control was also obtained for radioresistant cancer of the base of the skull. Preliminary clinical data seem to confirm the expected therapeutic gain with light ions, due to their ballistic and radio-biological properties, and justify the European projects for the construction of dedicated medical facilities for cancers. The French "Etoile" project will be integrated in the European hadrontherapy network "Enlight", with the objectives to coordinate technologic, medical and economic features.

Importance of hypoxia in the biology and treatment of brain tumors

The resistance of gliomas to treatment with radiation and antineoplastic drugs may result in part from the effects of the extensive, severe hypoxia that is present in these tumors. It is clear that brain tumors contain extensive regions in which the tumor cells are subjected to unphysiological levels of hypoxia. Hypoxic cells are resistant to radiation. Hypoxia and the perfusion deficits and metabolic changes that accompany hypoxia in vivo also produce resistance to many commonly used anticancer drugs. The resistance of cells that are hypoxic at the time of therapy may influence the efficacy of the treatment of these tumors with radiation, chemotherapy, and combined modality regimens. Moreover, it is becoming increasingly evident from laboratory studies that exposure of cells to adverse microenvironments produces transient changes in gene expression, induces mutations, and selects for cells with altered genotypes, thus driving the evolution of the cell population toward increasing malignancy and increasingly aggressive phenotypes. Hypoxia may therefore be involved in the evolution of cells in low-grade malignancies to the resistant, aggressive phenotype characteristic of glioblastomas. During the past 50 years, many attempts have been made to circumvent the therapeutic resistance induced by hypoxia, by improving tumor oxygenation, by using oxygen-mimetic radiosensitizers, by adjuvant therapy with drugs that are preferentially toxic to hypoxic cells, by using hyperthermia, or by devising radiation sources and regimens that are less affected by hypoxia. Past clinical trials have provided tantalizing suggestions that the outcome of therapy can be improved by many of these approaches, but none has yet produced a significant, reproducible improvement in the therapeutic ratio, which would be needed for any of these approaches to become the standard therapy for these diseases. Several ongoing clinical trials are addressing other, hopefully better regimens; it will be interesting to see the results of these studies.

Intensity-modulated radiotherapy with an integrated boost to the macroscopic tumor volume in the treatment of high-grade gliomas

Integrated boost radiotherapy (IBRT) delivers a higher fraction size to the gross tumor volume and a conventional fraction size to the surrounding tissue of microscopic spread. We compared stereotactic conformal radiotherapy (SCRT) and intensity-modulated radiotherapy (IMRT) with regard to their suitability for IBRT in the treatment of high-grade gliomas. In 20 patients treated with conventional radiotherapy, an additional treatment plan for IBRT [planning target volume (PTV1) defined as contrast-enhancing lesion plus margin due to setup errors 75 Gy, PTV2 defined as edema plus margin due to microscopic spread and setup error 60 Gy] with 7 non-coplanar beams for IMRT and for SCRT was carried out and compared. The part of the PTV2 irradiated with more than 107% of the prescribed dose was 13.9% for IMRT and 30.9% for SCRT (P < 0.001). Dose coverage of PTV2 (volume above 95% of the prescribed dose) was improved with IMRT (88.4% vs. 75.3% with SCRT, P < 0.001). Dose coverage of PTV1 was slightly higher with SCRT (93.7% vs. 87.5% with IMRT), but the conformity to the boost shape was improved by IMRT [conformity index (COIN95) = 0.85 vs. 0.69 with SCRT]. Simultaneously the brain volume irradiated with > 50 Gy was reduced from 60 to 33 cc (P < 0.001). We conclude that IMRT is suitable for local dose escalation in the enhancing lesion and for delivering a homogeneous dose to the PTV2 outside the PTV1 at the same time. Our encouraging results justify application of IMRT for IBRT in the treatment of high-grade gliomas. For clinical evaluation a phase III study has been initiated.

Accelerated fractionated proton/photon irradiation to 90 cobalt gray equivalent for glioblastoma multiforme: results of a phase II prospective trial

OBJECT

After conventional doses of 55 to 65 Gy of fractionated irradiation, glioblastoma multiforme (GBM) usually recurs at its original location. This institutional phase II study was designed to assess whether dose escalation to 90 cobalt gray equivalent (CGE) with conformal protons and photons in accelerated fractionation would improve local tumor control and patient survival.

METHODS

Twenty-three patients were enrolled in this study. Eligibility criteria included age between 18 and 70 years, Karnofsky Performance Scale score of greater than or equal to 70, residual tumor volume of less than 60 ml, and a supratentorial, unilateral tumor. Actuarial survival rates at 2 and 3 years were 34% and 18%, respectively. The median survival time was 20 months, with four patients alive 22 to 60 months postdiagnosis. Analysis by Radiation Therapy Oncology Group prognostic criteria or Medical Research Council indices showed a 5- to 11-month increase in median survival time over those of comparable conventionally treated patients. All patients developed new areas of gadolinium enhancement during the follow-up period. Histological examination of tissues obtained at biopsy, resection, or autopsy was conducted in 15 of 23 patients. Radiation necrosis only was demonstrated in seven patients, and their survival was significantly longer than that of patients with recurrent tumor (p = 0.01). Tumor regrowth occurred most commonly in areas that received doses of 60 to 70 CGE or less; recurrent tumor was found in only one case in the 90-CGE volume.

CONCLUSIONS

A dose of 90 CGE in accelerated fractionation prevented central recurrence in almost all cases. The median survival time was extended to 20 months, likely as a result of central control. Tumors will usually recur in areas immediately peripheral to this 90-CGE volume, but attempts to extend local control by enlarging the central volume are likely to be limited by difficulties with radiation necrosis.