The distribution of vascular endothelial growth factor-producing cells in clinical radiation necrosis of the brain: pathological consideration of their potential roles

Radionecrosis of malignant glioma and cerebral metastasis: a diagnostic challenge in MRI

Detecting a new area of contrast-enhancement at MRI after irradiation of malignant brain tumor arises the problem of differential diagnosis between tumor recurrence and radiation necrosis induced by the treatment. The challenge for imaging is to distinguish the two diagnoses given: the prognostic and therapeutic issues. Various criteria have been proposed in the literature based on morphological, functional or metabolic MRI. The purpose of this study was to perform an analysis of these tools to identify MRI best criteria to differentiate radiation necrosis lesions from malignant gliomas and brain metastases recurrence. For gliomas, the morphology of the contrast-enhancement cannot guide the diagnosis and the use of perfusion techniques and spectroscopy (multivoxels if possible) are necessary. In the follow-up of metastasis, a transient increase and moderate lesion volume is possible with a good prognosis. Morphological characteristics (volume ratio T2/T1Gd) and perfusion analysis provide valuable tools for approaching the diagnosis of radionecrosis.

The diagnosis and treatment of pseudoprogression, radiation necrosis and brain tumor recurrence

Radiation therapy is an important modality used in the treatment of patients with brain metastatic disease and malignant gliomas. Post-treatment surveillance often involves serial magnetic resonance imaging. A challenge faced by clinicians is in the diagnosis and management of a suspicious gadolinium-enhancing lesion found on imaging. The suspicious lesion may represent post-treatment radiation effects (PTRE) such as pseudoprogression, radiation necrosis or tumor recurrence. Significant progress has been made in diagnostic imaging modalities to assist in differentiating these entities. Surgical and medical interventions have also been developed to treat PTRE. In this review, we discuss the pathophysiology, clinical presentation, diagnostic imaging modalities and provide an algorithm for the management of pseudoprogression, radiation necrosis and tumor recurrence.

Inflammation as well as angiogenesis may participate in the pathophysiology of brain radiation necrosis

Radiation necrosis (RN) after intensive radiation therapy is a serious problem. Using human RN specimens, we recently proved that leaky angiogenesis is a major cause of brain edema in RN. In the present study, we investigated the same specimens to speculate on inflammation's effect on the pathophysiology of RN. Surgical specimens of symptomatic RN in the brain were retrospectively reviewed by histological and immunohistochemical analyses using hematoxylin and eosin (H&E) staining as well as immunohistochemical staining for VEGF, HIF-1α, CXCL12, CXCR4, GFAP, CD68, hGLUT5, CD45, IL-1α, IL-6 TNF-α and NF-kB. H&E staining demonstrated marked angiogenesis and cell infiltration in the perinecrotic area. The most prominent vasculature was identified as thin-walled leaky angiogenesis, i.e. telangiectasis surrounded by prominent interstitial edema. Two major cell phenotypes infiltrated the perinecrotic area: GFAP-positive reactive astrocytes and CD68/hGLUT5-positive cells (mainly microglias). Immunohistochemistry revealed that CD68/hGLUT5-positive cells and GFAP-positive cells expressed HIF-1α and VEGF, respectively. GFAP-positive cells expressed chemokine CXCL12, and CD68/hGLUT5-positive cells expressed receptor CXCR4. The CD68/hGLUT5-positive cells expressed pro-inflammatory cytokines IL-1α, IL-6 and TNF-α in the perinecrotic area. VEGF caused leaky angiogenesis followed by perilesional edema in RN. GFAP-positive cells expressing CXCL12 might attract CXCR4-expressing CD68/hGLUT5-positive cells into the perinecrotic area. These accumulated CD68/hGLUT5-positive cells expressing pro-inflammatory cytokines seemed to aggravate the RN edema. Both angiogenesis and inflammation might be caused by the regulation of HIF-1α, which is well known as a transactivator of VEGF and of the CXCL12/CXCR4 chemokine axis.

Bevacizumab treatment leads to observable morphological and metabolic changes in brain radiation necrosis

We investigated morphological and metabolic changes of radiation necrosis (RN) of the brain following bevacizumab (BEV) treatment by using neuroimaging. Nine patients with symptomatic RN, who had already been treated with radiation therapy for malignant brain tumors (6 glioblastomas, 1 anaplastic oligodendroglioma, and 2 metastatic brain tumors), were enrolled in this prospective clinical study. RN diagnosis was neuroradiologically determined with Gd-enhanced MRI and 11C-methionine positron emission tomography (MET-PET). RN clinical and radiological changes in MRI, magnetic resonance spectroscopy (MRS) and PET were assessed following BEV therapy. Karnofsky performance status scores improved in seven patients (77.8 %). Both volumes of the Gd-enhanced area and FLAIR-high area from MRI decreased in all patients after BEV therapy and the mean size reduction rates of the lesions were 80.0 and 65.0 %, respectively. MRS, which was performed in three patients, showed a significant reduction in Cho/Cr ratio after BEV therapy. Lesion/normal tissue (L/N) ratios in MET- and 11C-choline positron emission tomography (CHO-PET) decreased in 8 (89 %) and 9 patients (100 %), respectively, and the mean L/N ratio reduction rates were 24.4 and 60.7 %, respectively. BEV-related adverse effects of grade 1 or 2 (anemia, neutropenia and lymphocytopenia) occurred in three patients. These results demonstrated that BEV therapy improved RN both clinically and radiologically. BEV therapeutic mechanisms on RN have been suggested to be related not only to the effect on vascular permeability reduction by repairing the blood-brain barrier, but also to the effect on suppression of tissue biological activity, such as immunoreactions and inflammation.

The roles of platelet-derived growth factors and their receptors in brain radiation necrosis

Background

Brain radiation necrosis (RN) occurring after radiotherapy is a serious complication. We and others have performed several treatments for RN, using anticoagulants, corticosteroids, surgical resection and bevacizumab. However, the mechanisms underlying RN have not yet been completely elucidated. For more than a decade, platelet-derived growth factors (PDGFs) and their receptors (PDGFRs) have been extensively studied in many biological processes. These proteins influence a wide range of biological responses and participate in many normal and pathological conditions. In this study, we demonstrated that PDGF isoforms (PDGF-A, B, C, and D) and PDGFRs (PDGFR-α and β) are involved in the pathogenesis of human brain RN. We speculated on their roles, with a focus on their potential involvement in angiogenesis and inflammation in RN.

Methods

Seven surgical specimens of RN, obtained from 2006 to 2013 at our department, were subjected to histopathological analyses and stained with hematoxylin and eosin. We qualitatively analyzed the protein expression of each isoform of PDGF by immunohistochemistry. We also examined their expression with double immunofluorescence.

Results

All PDGFs were expressed in macrophages, microglia, and endothelial cells in the boundary of the core of RN, namely, the perinecrotic area (PN), as well as in undamaged brain tissue (UB). PDGF-C, D and PDGFR-α were also expressed in reactive astrocytes in PN. PDGFs and PDGFR-α were scarcely detected in UB, but PDGFR-β was specifically expressed in endothelial cells not only in PN but also in UB.

Conclusions

PDGFs/PDGFRs play critical roles in angiogenesis and possibly in inflammation, and they contribute to the pathogenesis of RN, irrespective of the original tumor pathology and applied radiation modality. Treatments for the inhibition of PDGF-C, PDGF-D, and PDGFR-α may provide new approaches for the treatment of RN induced by common radiation therapies.

An analysis of radiation necrosis of the central nervous system treated with bevacizumab

Radiation necrosis is a devastating complication following radiation to the central nervous system. The purpose of this study was to perform a comprehensive analysis of cases in the literature using bevacizumab, a monoclonal antibody against vascular endothelial growth factor, as treatment for radiation necrosis. A MEDLINE/PubMed search of articles about the use of bevacizumab for radionecrosis treatment yielded 16 studies published between 2007 and 2012. Data was summarized according to patient characteristics, treatment received and outcomes measured. A total of 71 unique cases were identified that met the inclusion criteria. The median age at the time of treatment with bevacizumab was 47 years. The most common tumors treated were glioblastoma (31 %), anaplastic glioma (14 %), and metastatic brain tumors (15 %). The median time from ending radiotherapy to starting treatment with bevacizumab was 11 months and the median follow up time after bevacizumab treatment was 8 months. The median number of cycles of bevacizumab was administered was 4, and the median dosage of bevacizumab was 7.5 mg/kg. The median time elapsed between cycles of bevacizumab was 2 weeks. Overall, pre and post treatment imaging revealed a median decrease in T1 contrast enhancement of 63 %, and a 59 % median decrease in T2/FLAIR signal abnormality. Treatment with bevacizumab resulted in a significant radiographic response for patients with radionecrosis. The median dosage of bevacizumab of 7.5 mg/kg for four cycles every 2 weeks should be considered as a treatment option in this patient population.

Boron neutron capture therapy with bevacizumab may prolong the survival of recurrent malignant glioma patients: four cases

Background and importance

Recurrent malignant gliomas (RMGs) are very difficult to control, and no standard treatments have been established for them. We performed boron neutron capture therapy (BNCT) for patients with RMG. BNCT enables high-dose particle radiation to be applied selectively to tumor cells. However, RMG cases generally receive nearly 60 Gy X-ray irradiation prior to re-irradiation by BNCT. Therefore, even with tumor-selective particle radiation BNCT, radiation necrosis in the brain and symptomatic pseudoprogression may develop. In four of our recent patients with RMG after BNCT, we applied the anti-VEGF antibody bevacizumab to treat two pathological entities. This approach appeared to prolong survival. Here we present the case reports of these four consecutive patients with RMG and discuss the novel use of bevacizumab in this context.

Clinical presentation

Four patients with RMGs were treated with BNCT at our institutes. Upon the referral for BNCT, they were assessed as belonging to the recursive partitioning analysis (RPA) class 3 (n = 3 patients) or RPA class 4 (n = 1 patient) (the RPA classification for RMG was advocated by Carson et al. in 2007). The estimated median survival times for RPA classes 3 and 4 were 3.8 and 10.8 months, respectively, after some treatment at the recurrence. We applied BNCT for these four patients and administered bevacizumab when the lesions were considered radiation necrosis or symptomatic pseudoprogression. The class 3 patients survived after the BNCT for 14, 16.5 and > 23 months, and the class 4 patient survived > 26 months, with favorable improvements in clinical symptoms.

Conclusion

BNCT with the addition of bevacizumab for radiation necrosis or symptomatic pseudoprogression improved the clinical symptoms and prolonged the survival in RMG patients.

Bevacizumab as a treatment for radiation necrosis of brain metastases post stereotactic radiosurgery

BACKGROUND

Cerebral radiation necrosis (RN) is a difficult to treat complication of stereotactic radiosurgery (SRS) that can result in progressive neurologic decline. Currently, steroids are the standard of care treatment for brain RN despite their adverse effect profile and limited efficacy. The purpose of this study was to evaluate the treatment efficacy of cerebral RN to bevacizumab in patients with brain metastases previously treated with SRS.

METHODS

We retrospectively reviewed 14 lesions in 11 patients treated with bevacizumab for brain RN secondary to SRS for their brain metastases. Steroid dosing, RN-associated symptoms, and magnetic resonance imaging (MRI) scans were examined before, during, and after bevacizumab administration.

RESULTS

Of the 11 patients included, 6 had metastatic non-small cell lung cancer, and 5 had metastatic breast cancer. The mean percentage decrease in RN volume seen on T1 post-Gadolinium and fluid-attenuated inversion recovery (FLAIR) MRI at first follow-up, at a mean of 26 days (range, 15-43 days), was 64.4% and 64.3%, respectively. MRI changes were sustained on follow-up MRI scans, obtained at a mean of 33 days (range, 7-58 days) after bevacizumab discontinuation. After bevacizumab treatment, all patients initially receiving steroids had a reduction in steroid requirement, and all but one had an improvement in or stability of RN-associated symptoms. No patients experienced intratumoral bleeds or other adverse effects related to their bevacizumab treatment.

CONCLUSIONS

Bevacizumab is effective and safe for the treatment of RN after SRS for brain metastasis. In this context, bevacizumab offers symptomatic relief, a reduction in steroid requirement, and a dramatic radiographic response.

Drug review: Safety and efficacy of bevacizumab for glioblastoma and other brain tumors

Glioblastoma is a highly vascular tumor that expresses vascular endothelial growth factor, a key regulator of angiogenesis and tumor blood vessel permeability. Bevacizumab is a monoclonal antibody that inhibits vascular endothelial growth factor and the growth of gliomas. Bevacizumab monotherapy has proven effective for recurrent glioblastoma, and it extended progression-free survival and improved patient quality of life in various clinical trials. Some patients who receive bevacizumab experience improvements in neurological symptoms and steroid dose reductions. Bevacizumab induces a dramatic and rapid radiological response, but non-enhancing lesions are often detected on magnetic resonance imaging without enhancing lesions. Rebound phenomena such as rapid tumor regrowth are occasionally observed after the discontinuation of bevacizumab therapy. Therefore, Response Assessment in Neuro-Oncology criteria were recently devised to evaluate the efficacy and radiological response of bevacizumab treatment. Hypertension and proteinuria are characteristic adverse events associated with bevacizumab therapy. In addition, many fatal adverse events such as intracranial hemorrhage and venous thromboembolism are reported in patients treated with bevacizumab. However, these events are also associated with glioma itself, and careful attention needs to be paid to these events. Bevacizumab is used to treat various diseases including radiation necrosis and recurrent brain tumors such as brain metastases, schwannoma and meningioma, but additional clinical trials are necessary. The efficacy and current problems associated with bevacizumab in the treatment of glioblastoma and other brain tumors are reviewed.

Bevacizumab treatment of symptomatic pseudoprogression after boron neutron capture therapy for recurrent malignant gliomas. Report of 2 cases

BACKGROUND

Bevacizumab, an anti-vascular endothelial growth factor antibody, has been used for the treatment of radiation necrosis. Thus far, however, there has been no definitive report on its use for the treatment of symptomatic pseudoprogression. Here we report 2 cases of successful treatment with bevacizumab for symptomatic pseudoprogression after boron neutron capture therapy (BNCT) was applied for recurrent malignant gliomas.

METHODS

Two recurrent malignant gliomas received BNCT. Both cases were treated with intravenous administration of bevacizumab at the deterioration that seemed to be symptomatic pseudoprogression.

RESULTS

The first case was recurrent glioblastoma multiforme and the second was recurrent anaplastic oligoastrocytoma. Both cases recurred after standard chemoradiotherapy and were referred to our institute for BNCT, which is tumor-selective particle radiation. Just prior to neutron irradiation, PET with an amino acid tracer was applied in each case to confirm tumor recurrence. Both cases showed deterioration in symptoms, as well as on MRI, at intervals of 4 months and 2 months, respectively, after BNCT. For the first case, a second PET was applied in order to confirm no increase in tracer uptake. We diagnosed both cases as symptomatic pseudoprogression and started the intravenous administration of 5 mg/kg bevacizumab biweekly with 6 cycles. Both cases responded well to this, showing rapid and dramatic improvement in neuroimaging and clinical symptoms. No tumor progression was observed 8 months after BNCT.

CONCLUSIONS

Bevacizumab showed marked effects on symptomatic pseudoprogression after BNCT. BNCT combined with bevacizumab may prolong the survival of patients with recurrent malignant gliomas.

Cerebral radiation necrosis: a review of the pathobiology, diagnosis and management considerations

Radiation therapy forms one of the building blocks of the multi-disciplinary management of patients with brain tumors. Improved survival following radiation therapy may come with a cost, including the potential complication of radiation necrosis. Radiation necrosis impacts the quality of life in cancer survivors, and it is essential to detect and effectively treat this entity as early as possible. Significant progress in neuro-radiology and molecular pathology facilitate more straightforward diagnosis and characterization of cerebral radiation necrosis. Several therapeutic interventions, both medical and surgical, may halt the progression of radiation necrosis and diminish or abrogate its clinical manifestations, but there are still no definitive guidelines to follow explicitly that guide treatment of radiation necrosis. We discuss the pathobiology, clinical features, diagnosis, available treatment modalities, and outcomes in the management of patients with intracranial radiation necrosis that follows radiation used to treat brain tumors.

Bevacizumab treatment for symptomatic radiation necrosis diagnosed by amino acid PET

Bevacizumab is effective in treating radiation necrosis; however, radiation necrosis was not definitively diagnosed in most previous reports. Here we used amino acid positron emission tomography to diagnose radiation necrosis for the application of bevacizumab in treating progressive radiation necrosis. Lesion/normal tissue ratios of <2.5 on (18)fluoride-labeled boronophenylalanine-positron emission tomography were defined as an indication of effective bevacizumab treatment. Thirteen patients were treated with bevacizumab at a dose of 5 mg/kg every 2 weeks. Two patients were excluded because of adverse events. The median reduction rate in perilesional edema was 65.5%. Karnofsky performance status improved in six patients after bevacizumab treatment. Lesion/normal tissue ratios on (18)fluoride-labeled boronophenylalanine-positron emission tomography (P = 0.0084) and improvement in Karnofsky performance status after bevacizumab treatment (P = 0.0228) were significantly associated with reduced rates of perilesional edema. Thus, (18)fluoride-labeled boronophenylalanine-positron emission tomography could be useful for diagnosing radiation necrosis and predicting the efficacy of bevacizumab in progressive radiation necrosis.

Bevacizumab used for the treatment of severe, refractory perilesional edema due to an arteriovenous malformation treated with stereotactic radiosurgery

The authors present a case of an arteriovenous malformation of the central sulcus treated with Gamma Knife surgery. The patient developed perilesional edema 9 months after treatment and experienced severe headache and hemiparesis. Her symptoms were refractory to corticosteroid therapy and pain management. She was subsequently treated with bevacizumab with striking improvement in her symptoms and results of neuroimaging studies. This is the first time that bevacizumab has been used to control severe refractory perilesional edema related to an intracranial arteriovenous malformation.

Antiangiogenic therapy for glioblastoma

Glioblastomas are among the most vascular tumors due to the expression of a variety of proangiogenic factors. New drug regimens are being developed to target angiogenesis in an attempt to arrest tumor growth. In particular, the vascular endothelial growth factor (VEGF) pathway has been a prime drug target. Preliminary results with anti-VEGF agents have been promising with prolonged progression-free survival reported. In addition, the antipermeability effects of anti-VEGF agents have important consequences for tumor imaging and for patient quality of life by decreasing corticosteroid dependence. Unfortunately, the response to anti-VEGF therapy is transient, and the majority of patients eventually relapsed, so more work is needed to understand the mechanisms of tumor escape.