Intraoperative radiation therapy for malignant glioma

Efficacy and Safety of Intraoperative Radiotherapy for High-Grade Gliomas: A Systematic Review and Meta-Analysis

BACKGROUND AND OBJECTIVES

High-grade gliomas (HGGs) are aggressive tumors of the central nervous system that cause significant morbidity and mortality. Despite advances in surgery and radiation therapy (RT), HGG still has a high incidence of recurrence and treatment failure. Intraoperative radiotherapy (IORT) has emerged as a promising therapeutic approach to achieve local tumor control while sparing normal brain tissue from radiation-induced damage.

METHODS

A systematic review and meta-analysis were conducted following PRISMA guidelines to evaluate the use of IORT for HGG. Eligible studies were included based on specific criteria, and data were independently extracted. Outcomes of interest included complications, IORT failure, survival rates at 12 and 24 months, and mortality.

RESULTS

Sixteen studies comprising 436 patients were included. The overall complication rate after IORT was 17%, with significant heterogeneity observed. The IORT failure rate was 77%, while the survival rates at 12 and 24 months were 74% and 24%, respectively. The mortality rate was 62%.

CONCLUSION

This meta-analysis suggests that IORT may be a promising adjuvant treatment for selected patients with HGG. Despite the high rate of complications and treatment failures, the survival outcomes were comparable or even superior to conventional methods. However, the limitations of the study, such as the lack of a control group and small sample sizes, warrant further investigation through prospective randomized controlled trials to better understand the specific patient populations that may benefit most from IORT. However, the limitations of the study, such as the lack of a control group and small sample sizes, warrant further investigation. Notably, the ongoing RP3 trial (NCT02685605) is currently underway, with the aim of providing a more comprehensive understanding of IORT. Moreover, future research should focus on managing complications associated with IORT to improve its safety and efficacy in treating HGG.

Application of intraoperative radiotherapy for malignant glioma

Malignant glioma is characterized by rapid tumor cell proliferation and high recurrence risk. In terms of its treatment, the therapeutic effects of maximum resection and postoperative radiotherapy with adjuvant chemotherapy as well as many other new therapeutic techniques such as antiangiogenic therapy and immunotherapy remain poor. Glioma recurrence, especially local recurrence, is an important reason of glioma treatment failure. Intraoperative radiotherapy (IORT) enables exclusion of radiation-sensitive normal tissue from the radiation field in operation and then the application of a single high-dose precision irradiation to the residual tumor or tumor bed. IORT has great application potential in the control of local recurrence of malignant tumors. This paper thus aims to review the current status and prospects of IORT's application in malignant glioma treatment.

The Efficacy and Safety of Intraoperative Radiotherapy in the Treatment of Recurrent High-Grade Glioma: A Single-Center Prospective Study

BACKGROUND

High-grade gliomas are treated following a standard protocol; however, tumor recurrence is almost inevitable. Recurrent high-grade gliomas have an extremely poor prognosis, and there are no clear treatment guidelines. In this stud, we evaluated the safety and effectiveness of intraoperative radiotherapy (IORT) for recurrent high-grade glioma.

METHODS

In this prospective randomized study begun in April 2018, patients ≥18 years of age with a Karnofsky Performance Status >50 and recurrent high-grade glioma were randomly assigned in a 1:1 ratio to tumor resection and IORT or tumor resection alone.

RESULTS

Twenty-two patients were allocated to the IORT group and 21 to receive surgery only (operation group). Clinical data of 42 enrolled patients were involved in the analysis. The progression-free survival of the IORT group was 9.6 months and of the operation group was 7.3 months (P = 0.018), and the overall survival of the 2 groups was 13.5 months and 10.2 months, respectively (P = 0.054). Univariate and multivariate analysis indicated that preoperative Karnofsky Performance Status >70 and IORT were protective factors for patients with recurrent high-grade glioma. A patient who underwent conventional fractionated radiotherapy within 6 months of receiving IORT died on the ninth day after undergoing tumor resection and IORT because of severe cerebral edema. The total operation time was longer in the IORT group, but there were no differences in intraoperative bleeding or adverse events between the 2 groups.

CONCLUSIONS

IORT with low-energy radiography at a dose of 30-40 Gy is generally safe and effective for patients with recurrent glioma. However, IORT should not be performed for patients who have received conventional fractionated radiotherapy within 6 months.

Surgical Treatment of Glioblastoma: State-of-the-Art and Future Trends

Glioblastoma (GBM) is a highly aggressive disease and is associated with poor prognosis despite treatment advances in recent years. Surgical resection of tumor remains the main therapeutic option when approaching these patients, especially when combined with adjuvant radiochemotherapy. In the present study, we conducted a comprehensive literature review on the state-of-the-art and future trends of the surgical treatment of GBM, emphasizing topics that have been the object of recent study.

The American Brachytherapy Society consensus statement on intraoperative radiation therapy

PURPOSE

Although radiation therapy has traditionally been delivered with external beam or brachytherapy, intraoperative radiation therapy (IORT) represents an alternative that may shorten the course of therapy, reduce toxicities, and improve patient satisfaction while potentially lowering the cost of care. At this time, there are limited evidence-based guidelines to assist clinicians with patient selection for IORT. As such, the American Brachytherapy Society presents a consensus statement on the use of IORT.

METHODS

Physicians and physicists with expertise in intraoperative radiation created a site-directed guideline for appropriate patient selection and utilization of IORT.

RESULTS

Several IORT techniques exist including radionuclide-based high-dose-rate, low-dose-rate, electron, and low-energy electronic. In breast cancer, IORT as monotherapy should only be used on prospective studies. IORT can be considered in the treatment of sarcomas with close/positive margins or recurrent sarcomas. IORT can be considered in conjunction with external beam radiotherapy for retroperitoneal sarcomas. IORT can be considered for colorectal malignancies with concern for positive margins and in the setting of recurrent gynecologic cancers. For thoracic, head and neck, and central nervous system malignancies, utilization of IORT should be evaluated on a case-by-case basis.

CONCLUSIONS

The present guidelines provide clinicians with a summary of current data regarding IORT by treatment site and guidelines for the appropriate patient selection and safe utilization of the technique. High-dose-rate, low-dose-rate brachytherapy methods are appropriate when IORT is to be delivered as are electron and low-energy based on the clinical scenario.

[Repetitive resection and intrasurgery radiation therapy of brain malignant gliomas: history of question and modern state of problem]

Numerous studies have shown that the degree of primary resection of malignant gliomas of the brain (MG) directly correlates with rates of relapse-free and overall patient survival. Currently, there is no unequivocal opinion regarding the indications and effectiveness of repeated resection in relapse of MG after combined treatment. Surgical intervention, taking into account the pathomorphological features of these tumors, is not healing and should be supplemented with certain methods of adjuvant treatment. The article reviews and analyzes publications devoted to repeated resection and various methods of intraoperative radiation therapy in the treatment of MG. Based on the analysis, the authors of the article came to the conclusion that it is advisable to start their own research on the use of intraoperative balloon brachytherapy in the treatment of recurrent MG based on modern technological solutions.

Repeat Resection and Intraoperative Radiotherapy for Malignant Gliomas of the Brain: A History and Review of Current Techniques

The degree of primary resection of malignant brain gliomas (MBGs) has correlated positively with progression-free and overall survival. The indications for surgery and reoperation in MBG relapse remain controversial. Surgery will not be curative and should be followed by adjuvant treatment. We reviewed the reported studies with respect to repeat resection and the various methods of intraoperative radiotherapy for MBGs from the initial experience with high-energy linear accelerators in Japan to modern, integrated brachytherapy solutions using solid and balloon applicators. Because of the findings from our review, we have begun to research into the use of intraoperative balloon brachytherapy for recurrent MBGs.

Immunotherapy Combined with Large Fractions of Radiotherapy: Stereotactic Radiosurgery for Brain Metastases-Implications for Intraoperative Radiotherapy after Resection

Brain metastases (BM) affect approximately a third of all cancer patients with systemic disease. Treatment options include surgery, whole-brain radiotherapy, or stereotactic radiosurgery (SRS) while chemotherapy has only limited activity. In cases where patients undergo resection before irradiation, intraoperative radiotherapy (IORT) to the tumor bed may be an alternative modality, which would eliminate the repopulation of residual tumor cells between surgery and postoperative radiotherapy. Accumulating evidence has shown that high single doses of ionizing radiation can be highly efficient in eliciting a broad spectrum of local, regional, and systemic tumor-directed immune reactions. Furthermore, immune checkpoint blockade (ICB) has proven effective in treating antigenic BM and, thus, combining IORT with ICB might be a promising approach. However, it is not known if a low number of residual tumor cells in the tumor bed after resection is sufficient to act as an immunizing event opening the gate for ICB therapies in the brain. Because immunological data on tumor bed irradiation after resection are lacking, a rationale for combining IORT with ICB must be based on mechanistic insight from experimental models and clinical studies on unresected tumors. The purpose of the present review is to examine the mechanisms by which large radiation doses as applied in SRS and IORT enhance antitumor immune activity. Clinical studies on IORT for brain tumors, and on combined treatment of SRS and ICB for unresected BM, are used to assess the safety, efficacy, and immunogenicity of IORT plus ICB and to suggest an optimal treatment sequence.

First Experience of Intraoperative Radiation Therapy in Cerebral High Grade Glioma in Iran: A Report of Three Cases and Literature Review

Introduction:

Among the high grade cerebral gliomas, Glioblastoma multiform for instance, would be the main pattern of local recurrence causes clinical deterioration and deaths. This has observed 2 - 3 cm upon the initial lesion. During the period of 2 - 4 weeks post-surgery, remaining tumor cells have re-grown until radiochemotherapy has initiated. So it has seemed clear that improved local control could hopefully translate into improved survival. As a matter of fact, mass reduction has insufficiently achieved in almost every case of GBM as that the tumor cell number has not fallen below a “threshold” that tumor control might achieve by the host immune system.

Intraoperative Radiation therapy has been one of those add-on therapies, which has performed during or directly after resection and cleared the tumor cavity from microscopically remaining cells.

Although IORT has presented a novel and feasible principle, the method faced a number of technical and geometrical errors and limitations, which has decreased its potential in the reports of previous studies. Examples could be mentioned as incomplete target volume coverage that seemed as the greatest influence on survival, due to irradiation with an inadequate electron cone size, due to angle errors, or inadequately low energies. In contrast to the previously used forward-beaming electron cones, spherical irradiation sources were specifically attractive in brain tumor IORT, even in post resection cavities with normal complex shapes.

Case Presentation:

We have been reporting 3 cases of high grade gliomas, one recurrent GBM, one primary glioma grade III, and the last one recurrent Rhabdoid GBM, which have been fulfilling our entrance criteria of IORT procedure, by using spherical applicators, which has been increasingly discussed in recent studies.

Conclusions:

It was the first experience of intraoperative radiation therapy for cerebral malignant tumours in Iran. Finally, we had a brief overview on the past and present IORT strategies in the treatment of GBM.

INTRAGO: intraoperative radiotherapy in glioblastoma multiforme—a phase I/II dose escalation study

BACKGROUND

Glioblastoma multiforme (GBM) is the most frequent primary malignant brain tumor in adults. Despite multimodal therapies, almost all GBM recur within a narrow margin around the initial resected lesion. Thus, novel therapeutic intensification strategies must target both, the population of dispersed tumor cells around the cavity and the postoperative microenvironment. Intraoperative radiotherapy (IORT) is a pragmatic and effective approach to sterilize the margins from persistent tumor cells, abrogate post-injury proliferative stimuli and to bridge the therapeutic gap between surgery and radiochemotherapy. Therefore, we have set up INTRAGO, a phase I/II dose-escalation study to evaluate the safety and tolerability of IORT added to standard therapy in newly diagnosed GBM. In contrast to previous approaches, the study involves the application of isotropic low-energy (kV) x-rays delivered by spherical applicators, providing optimal irradiation properties to the resection cavity.

METHODS/DESIGN

INTRAGO includes patients aged 50 years or older with a Karnofsky performance status of at least 50% and a histologically confirmed (frozen sections) supratentorial GBM. Safety and tolerability (i.e., the maximum tolerated dose, MTD) will be assessed using a classical 3 + 3 dose-escalation design. Dose-limiting toxicities (DLT) are wound healing deficits or infections requiring surgical intervention, IORT-related cerebral bleeding or ischemia, symptomatic brain necrosis requiring surgical intervention and early termination of external beam radiotherapy (before the envisaged dose of 60 Gy) due to radiotoxicity. Secondary end points are progression-free and overall survival.

TRIAL REGISTRATION

The study is registered with clinicaltrials.gov, number: NCT02104882 (Registration Date: 03/26/2014).

Intra-operative electron beam radiotherapy for newly diagnosed and recurrent malignant gliomas: feasibility and long-term outcomes

INTRODUCTION

Intra-operative electron beam radiotherapy (IOERT) is an alternative to dose escalation for the treatment of central nervous system tumors. The objective of this study was to describe the feasibility and long-term outcomes of IOERT in the treatment of primary and recurrent gliomas.

MATERIALS AND METHODS

From January 1992 through December 2002, all patients treated with IOERT at the Hospital San Francisco de Asis, Madrid/Spain were retrospectively reviewed. The selection criteria included patients with superficial tumors, KPS >70 % and lesions <6 cm. Irradiation was administered in one section. The prescribed dose considered the amount of post-resection residual tumor, previous radiotherapy and the tolerance level of brain structures exposed to IOERT.

RESULTS

There were 17 patients (53 %) with newly diagnosed malignant brain gliomas and 15 patients with recurrent tumors. The delivered dose varied from 8 to 20 Gy (median 12.5 Gy) for primary and from 8 to 16 Gy (median 10 Gy) for recurrent tumors. The median overall survival for the entire cohort was 13 months (14 and 10.4 months for the primary and recurrent, respectively). Three patients presented with radionecrosis, one patient with osteomyelitis at the craniotomy bone flap, one with intracerebral hemorrhage, and another patient experienced a pulmonary embolism.

CONCLUSIONS

IOERT is a feasible technique and can be viewed as a tool in the treatment of newly diagnosed or recurrent brain gliomas.

Stereotactic radiosurgery for patients with newly diagnosed glioblastoma multiforme (GBM): comparison with intra-operative radiotherapy and evaluation of prognostic factors

The goals of this study were (1) to compare, in a single institute, the clinical results of patients with newly diagnosed glioblastoma multiforme (GBM) treated with stereotactic radiosurgery (SRS), which has been incorporated into the initial management approach, with thosein-patientstreated with intra-operative radiotherapy (IORT) and (2) to assess whether these local irradiation boost therapies are prognostic factors on survival analysis. One hundred and twenty adult patients with supratentorial GBM had undergone tumour resection or biopsy and had received external beam radiotherapy (EBRT). Of them, 31 underwent IORT, 29 underwent SRS, and the remaining 60 had no local high-dose irradiation boost. The local irradiation boost led to clearly better results on survival of GBM patients. Furthermore, SRS is less invasive and allows for meticulous target planning of the irradiation boost, and was superior to IORT in terms of survival prolongation as well as suppression of local tumour recurrence/progression at the primary site in this series. In addition, SRS was a significant, positive prognostic factor for survival as well as gross-total resection of the tumour, and could be an alternative therapeutic modality to IORT for GBM.

Stereotactically Guided Fractionated Re-irradiation in Recurrent Glioblastoma Multiforme

PURPOSE

To assess the feasibility, efficacy and toxicity of fractionated stereotactic radiotherapy in the treatment of recurrent glioblastoma multiforme.

PATIENTS AND METHODS

From January 1995 to July 2003, 53 patients with histologically proven glioblastoma multiforme were treated at recurrence with fractionated stereotactic radiation therapy. A median dose of 36 Gy using a median fractionation of 5 x 2 Gy/week was applied.

RESULTS

Median overall survival was 21 months, and median overall survival from the time point of re-irradiation was 8 months. The median time interval between primary and secondary radiation therapy was 10 months. In this patient population, no variables predicting longer overall survival could be determined. However, neurosurgical resection at relapse was associated with increased survival after re-irradiation (p=0.04), but left progression-free survival unaltered. Treatment was well-tolerated and no severe toxicities developed.

CONCLUSION

Stereotactically guided fractionated re-irradiation is a safe and effective treatment modality in selected cases of recurring glioblastoma multiforme. Since this is not a randomized study, further evaluation in larger patient collectives is warranted. Also, based on recent results of radiochemotherapy in the treatment of primary glioblastoma multiforme, concomitant chemotherapy at relapse might be considered in the future.

Selection of eligible patients with supratentorial glioblastoma multiforme for gross total resection

The purpose of this study is to clarify whether gross total tumor resection can prolong the survival in adult patients with supratentorial glioblastoma multiforme (GBM), and to clarify what subset of these patients obtains a survival advantage by gross total tumor resection without postoperative neurological deterioration. Eighty-two adult patients with supratentorial GBM were retrospectively reviewed. Overall, the median survival time was 13 months, and the 1- and 2-year survival rates were 53.7% and 14.6%, respectively. In a univariate analysis for survival rate by log-rank test, age (< 40 years), Karnofsky performance scale (KPS) score (70-100%) and extent of surgery (gross total resection) were revealed to be significant good prognostic factors. A Cox proportional hazard multivariate regression analysis confirmed that the KPS and extent of surgery were independent, significant good prognostic factors. Nine patients (11%) suffered postoperative neurological deterioration. A topographical GBM staging system (Stages I, II and III) with the integration of tumor location, size and eloquence of adjacent brain based on MRI (for explanation of Stages see text) was originally proposed. In Stage I, gross total resection had a strong tendency toward a better prognostic factor in a univariate analysis and was revealed to be a significant independent good prognostic factor in a multivariate analysis. In also Stage II, the survival of patients who underwent gross total resection was better than that of patients with less than gross total resection, although not significant. In Stage III, there were no patients who underwent gross total tumor resection. Risk probabilities of postoperative neurological deterioration, overall, were 0%, 22.2%, and 20% in Stages I, II, and III, respectively, and those after gross total resection were 0% and 16.7% in Stages I and II, respectively. Although gross total tumor resection is associated with prolongation of the survival time of patients with GBM, the risk of postoperative neurological deficit increases with radical tumor resection. To select an eligible subset of patients that benefit in survival from gross total tumor resection without postoperative risk, the following surgical policy for GBM resection is suggested. GBM in Stage I should be resected as radically as possible. Regarding Stage II, risky surgical resection extending to the area adjacent to the critical zone should be avoided and more meticulous and careful surgical planning is needed than that in Stage I. In Stage III, radical gross total tumor resection is not recommended at present.

High-dose conformal radiotherapy influenced the pattern of failure but did not improve survival in glioblastoma multiforme

BACKGROUND AND PURPOSE

Although glioblastoma multiforme is clearly radiation-resistant, there is evidence of a dose-dependent response relationship. The purpose of the study was to evaluate the impact of higher dose by rotational multileaf collimator (MLC) conformal radiation therapy.

MATERIALS AND METHODS

From 1984 to 1995, 38 consecutive cases with intracranial glioblastoma multiforme were treated using the rotational MLC conformal therapy. There were 25 men and 13 women with a median age of 47 years (12-73 years, mean 46.5 years). Median Karnofsky performance score was 80 (30-100, mean 78.2). Median tumor volume was 64 cc (8-800 cc, mean 110.3 cc). All underwent surgical intervention (only biopsy in 1, partial resection in 13, subtotal resection in 21, and gross total resection in 3). Radiation dose to was 60 to 80 Gy (median 68.5 Gy, mean 68.3 Gy) in 21 patients treated before 1990 and 90 Gy in the 17 patients thereafter. Biweekly i.v. chemotherapy was also administered for both arms.

RESULTS

The 1-year, 2-year, 5-year, and 10-year overall survival rates were 75%, 42%, 20%, and 15%, respectively. Univariate analysis showed the initial tumor volume, residual tumor volume, and Karnofsky performance score were statistically significant factors for survival. Only the residual tumor volume was statistically significant by multivariate analysis. The 5-year survival rate of patients with residual tumors of 5 cc or less in volume was as good as 37%. Survival of the 90-Gy Group appeared inferior to that of the Low-Dose Group, though no statistical difference was seen (the 3-year survival was 40% vs. 22%). Local failure was observed in 16 of the 19 recurrences in the Low-Dose Group, whereas it was observed in only 4 of the 13 recurrences in the 90-Gy Group. The difference in pattern of failure was statistically significant. Two patients of the High-Dose Group developed radiation necrosis and one died of it.

CONCLUSIONS

The high-dose conformal radiotherapy did not improve survival in the disease, but did change the pattern of failure.

Longer survival in high grade gliomas: intraoperative radiation therapy (IORT) and immunocytochemical assessment of their growth potential

The authors report prolonged survival in patients with high grade (grade 3 and 4) gliomas who were given additional intraoperative radiation therapy (IORT) and discuss survival in relation to the immunocytochemical assessment of their tumours. Of 54 selected patients with high grade gliomas treated with multimodal therapy including IORT during the years from 1985 to 1989, 11 had long-term survival over 5 years after the initial treatment. The clinicopathological features, analysed retrospectively, that were associated with prolonged survival were: (1) epileptic seizures, (2) initial CT scans showing a small mass without contrast enhancement which developed into an enhancing larger mass on follow up, (3) tumour location which was frequently frontal and near the cortical surface, (4) 20-30 Gy irradiation (mean 25.5 Gy) in IORT delivered in one fraction to the post-resection tumour bed, and (5) a low proliferating cell nuclear antigen (PCNA) labelling index (LI). The most favourable prognostic indicator was found to be a low PCNA LI.

Intraoperative radiation therapy and Mohs micrographic surgery on an outpatient basis

BACKGROUND

Intraoperative radiation therapy (IORT) is used to deliver therapeutic doses of radiation to a surgically exposed tumor or tumor bed while minimizing the radiation dose to adjacent normal tissue. It is traditionally given with the patient under general anesthesia.

OBJECTIVE

To report a case of a recurrent squamous cell carcinoma treated with Mohs micrographic surgery and IORT on an outpatient basis.

METHODS

Mohs surgery was used to clear the tumor in all fields except for the area of the spinal accessory nerve, which was preserved. IORT was then delivered to the area of nerve with possible residual tumor.

RESULTS

The patient remains clinically tumor free 42 months posttreatment. There were no complications.

CONCLUSION

Intraoperative radiation therapy can be effectively used in the outpatient setting as an adjunctive therapy after Mohs micrographic surgery.

Effectiveness of intraoperative radiation therapy for recurrent supratentorial low grade glioma

Twelve adult patients in the records of 38 patients with histologically verified supratentorial low grade glioma showed recurrence at the Gifu University Hospital between 1980 and 1992. A mean period to recurrence from the initial surgery and postoperative radiation was 38 months. Six of these patients underwent intraoperative radiation therapy. The other six patients received chemotherapy with conventional cytoreductive surgery in three cases and additional external irradiation in three cases. The 2-year survival rate of the former patients was 83.8% and significantly higher than that of the latter ones, 16.7% (p < 0.05). Most cases showing recurrence of supratentorial low grade glioma were occurred locally, and dissemination or remote metastasis of the lesion were rare. The results revealed that the local control is important for recurrent tumors of supratentorial low grade gliomas. The effectiveness of the intraoperative radiation therapy as the second operation for the recurrent supratentorial benign glioma is discussed.

Intraoperative radiotherapy for gliomas

Intraoperative radiotherapy (IORT) was performed in 20 of 36 patients with glioma; 11 glioblastomas, 7 malignant astrocytomas, 2 benign astrocytomas. Twenty or 25 Gy of irradiation was delivered in a single fraction intraoperatively, followed by external beam irradiation. The electron beam energy was selected so that the 80% isodose line fell at 2 or 3 cm below the residual tumor surface. Median survival time of IORT group was 14 months and that of the control group was 10 months. Difference of survival curve was significant. There were 6 incidences of complication caused by IORT; 1 radionecrosis, 1 convulsion, 1 abscess, and 3 severe brain edemas. IORT is suited for the treatment of malignant gliomas.

Intra-operative radiation therapy for malignant brain tumors: rationale, method, and treatment results of cerebral glioblastomas

In radiation therapy for malignant brain tumours, the dose of radiation that can be safely delivered to a tumour is limited by the radiation tolerance of the adjacent normal brain tissue. Among various radiation modalities to produce local tumour eradication without unacceptable complications, we chose a large, single irradiation dose during the operation (intra-operative radiation therapy, IORT). In contrast to X-ray or Cobalt-60 gamma ray irradiation, IORT with a high-energy electron beam delivered by the Shimadzu 20 MeV betatron provides acceptable dose homogeneity with rapid fall-off of the radiation dose beyond the treatment volume. Thus, IORT has the advantage of precise demarcation of the target volume, minimum damage to surrounding normal tissues, and a high absorbed target dose (15-25 Gy in 5-10 min). On the basis of our experience with 170 patients treated by IORT, we established the treatment indications and method in patients with malignant brain tumours. IORT with a dose of 15-25 Gy was delivered to widely resected tumours followed by external radiation therapy. No acute or subacute complications were observed. Treatment results of 30 patients with glioblastoma treated by IORT (mean 18.3 Gy) combined with external radiation therapy (mean 58.5 Gy) resulted in a median survival of 119 weeks and a 2-year survival rate of 61%.