Magnetic resonance imaging in the evaluation of treatment-related central nervous system damage

Quantifying effects of radiotherapy-induced microvascular injury; review of established and emerging brain MRI techniques

Microvascular changes are increasingly recognised not only as primary drivers of radiotherapy treatment response in brain tumours, but also as an important contributor to short- and long-term (cognitive) side effects arising from irradiation of otherwise healthy brain tissue. As overall survival of patients with brain tumours is increasing, monitoring long-term sequels of radiotherapy-induced microvascular changes in the context of their potential predictive power for outcome, such as cognitive disability, has become increasingly relevant. Ideally, radiotherapy-induced significant microvascular changes in otherwise healthy brain tissue should be identified as early as possible to facilitate adaptive radiotherapy and to proactively start treatment to minimise the influence on these side-effects on the final outcome. Although MRI is already known to be able to detect significant long-term radiotherapy induced microvascular effects, more recently advanced MR imaging biomarkers reflecting microvascular integrity and function have been reported and might provide a more accurate and earlier detection of microvascular changes. However, the use and validation of both established and new techniques in the context of monitoring early and late radiotherapy-induced microvascular changes in both target-tissue and healthy tissue currently are minimal at best. This review aims to summarise the performance and limitations of existing methods and future opportunities for detection and quantification of radiotherapy-induced microvascular changes, as well as the relation of these findings with key clinical parameters.

Radiation-induced brain structural and functional abnormalities in presymptomatic phase and outcome prediction

Radiation therapy, a major method of treatment for brain cancer, may cause severe brain injuries after many years. We used a rare and unique cohort of nasopharyngeal carcinoma patients with normal-appearing brains to study possible early irradiation injury in its presymptomatic phase before severe, irreversible necrosis happens. The aim is to detect any structural or functional imaging biomarker that is sensitive to early irradiation injury, and to understand the recovery and progression of irradiation injury that can shed light on outcome prediction for early clinical intervention. We found an acute increase in local brain activity that is followed by extensive reductions in such activity in the temporal lobe and significant loss of functional connectivity in a distributed, large-scale, high-level cognitive function-related brain network. Intriguingly, these radiosensitive functional alterations were found to be fully or partially recoverable. In contrast, progressive late disruptions to the integrity of the related far-end white matter structure began to be significant after one year. Importantly, early increased local brain functional activity was predictive of severe later temporal lobe necrosis. Based on these findings, we proposed a dynamic, multifactorial model for radiation injury and another preventive model for timely clinical intervention. Hum Brain Mapp 39:407-427, 2018. © 2017 Wiley Periodicals, Inc.

Lesions of the central nervous system in leukemia: Pathological and magnetic resonance imaging features at presentation in 14 patients

The present study aimed to characterize the specific pathology and magnetic resonance imaging (MRI) findings observed in patients with leukemia with central nervous system (CNS) lesions, and to determine their value in the management of such patients. Lesions of the CNS were observed during and following treatment of leukemia. The data from stereotactic biopsy-proven pathology (12 patients) and MRI examinations (14 patients) were retrospectively evaluated. Proton-magnetic resonance-spectroscopy was performed in three patients. Factors that predisposed to lesions of the CNS were reviewed from the patient medical records. Among the 14 patients, eight had CNS leukemia, four had a CNS infection and two had a neurodegenerative disorder (one leukoencephalopathy and one glial cell hyperplasia). The clinical diagnosis based on clinical symptoms, signs and MRI features was not consistent with the pathological diagnosis in two patients. In one patient, the clinical diagnosis was a CNS infection; however, the patient's pathological diagnosis was CNS leukemia. In the other patient, the clinical diagnosis was CNS leukemia, but the pathological diagnosis was glial cell hyperplasia. CNS lesions in leukemia have a wide range of causes. Apart from the relapse of leukemia in the CNS, there are treatment-associated neurotoxicities and infections that are caused by immunocompromised states. As numerous leukemia-associated CNS lesions are treatable, early diagnosis is essential.

Hyperperfusion on magnetic resonance imaging in acute chemotherapy-related leukoencephalopathy

Acute chemotherapy-related leukoencephalopathy can present similar to acute stroke with symptoms including aphasia, dysarthria, and hemiplegia. Differentiation based on clinical appearance is challenging, and physicians must distinguish between the 2 conditions rapidly to institute appropriate therapies. An 8-year-old male with acute lymphoblastic leukemia receiving chemotherapy, including intrathecal methotrexate, presented to our emergency center with 2 hours of expressive aphasia and flaccid right hemiplegia. Emergent magnetic resonance imaging (MRI) was obtained, demonstrating diffusion restriction within bilateral corona radiata and centrum semiovale. Magnetic resonance perfusion revealed mildly increased perfusion, a finding inconsistent with ischemic stroke and previously unreported in acute chemotherapy-related leukoencephalopathy without necrosis. This increased perfusion conclusively eliminated stroke from the clinical differential. Magnetic resonance perfusion imaging proved valuable to rapidly distinguish acute chemotherapy-related leukoencephalopathy from ischemia, and the evaluation of perfusion alterations in this disorder may provide further insight into the pathophysiology of this entity.

Increased vulnerability of the spinal cord to radiation or intrathecal chemotherapy during adolescence: A report from the Children's Oncology Group

PURPOSE

To assess the rate of spinal cord toxicity in adolescents resulting from chemoradiotherapy of parameningeal sarcoma.

METHODS AND MATERIALS

Of 152 patients with parameningeal sarcoma treated per the Intergroup Rhabdomyosarcoma Study Group protocol from 1977 through 1989, eight developed paralyzing ascending myelitis after intrathecal chemotherapy with cytosine arabinoside, methotrexate, and hydrocortisone administered during and after radiation therapy to volumes that included part of the spinal cord. The eight cases include three not previously published.

RESULTS

Of eight patients who developed CNS toxicity after intrathecal chemotherapy and radiotherapy for parameningeal rhabdomyosarcoma, all but one were between 13 and 18 years of age when treated. This severe toxicity occurred in one quarter of 28 adolescents treated with the regimen in comparison with one of 123 children 12 years of age or less (P < 0.0001), a rate that was as much as 30 times higher in the adolescents. Lengthening of the spinal cord during the pubertal growth spurt may account for the apparent increased vulnerability.

CONCLUSIONS

Chemoradiotoxicity-associated spinal cord injury appears to be more likely to occur in adolescents than in younger or older ages. This observation appears to reverse a conventional wisdom in which the central nervous system is thought to become more resistant to the neurotoxic effects of chemoradiotherapy as it matures.

MR spectroscopy in radiation injury

Detecting a new area of contrast enhancement in or in the vicinity of a previously treated brain tumor always causes concern for both the patient and the physician. The question that immediately arises is whether this new lesion is recurrent tumor or a treatment effect. The differentiation of recurrent tumor or progressive tumor from radiation injury after radiation therapy is often a radiologic dilemma regardless the technique used, CT or MR imaging. The purpose of this article was to review the utility of one of the newer MR imaging techniques, MR spectroscopy, to distinguish recurrent tumor from radiation necrosis or radiation injury.

Metabolic alterations: a biomarker for radiation-induced normal brain injury-an MR spectroscopy study

PURPOSE

To assess if interval changes in metabolic status in normal cerebral tissue after radiation therapy (RT) can be detected by 2D CSI (chemical shift imaging) proton spectroscopy.

MATERIALS AND METHODS

Eleven patients with primary brain tumors undergoing cranial radiation therapy (RT) were included. 2D-CSI MRS was performed before, during, and after the course of RT with the following parameters: TE/TR 144/1500 ms, field of view (FOV) 24, thickness 10 mm, matrix 16 x 16. The metabolic ratios choline/creatine (Cho/Cr), N-acetylaspartate (NAA)/Cr, and NAA/Cho in normal brain tissue were calculated.

RESULTS

NAA/Cr and Cho/Cr were significantly decreased at week 3 during RT and at 1 month and 6 months after RT compared to values prior to RT (P < 0.01). The NAA/Cr ratio decreased by -0.19 +/- 0.05 (mean +/- standard error [SE]) at week 3 of RT, -0.14 +/- 0.06 at the last week of RT, -0.14 +/- 0.05 at 1 month after RT, and -0.30 +/- 0.08 at 6 months after RT compared to the pre-RT value of 1.43 +/- 0.04. The Cho/Cr ratio decreased by -0.27 +/- 0.05 at week 3 of RT, -0.11 +/- 0.05 at the last week of RT, -0.26 +/- 0.05 at 1 month after RT and -0.25 +/- 0.07 at 6 months after RT from the pre-RT value of 1.29 +/- 0.03. Changes in Cho/Cr were correlated with the interaction of the radiation dose and dose-volume at week 3 of RT, during the last week of RT (P < 0.005), and at 1 month after RT (P = 0.017).

CONCLUSION

The results of this study suggest that MRS can detect early metabolic changes in normal irradiated brain tissue.

Endoscopic removal of a central neurocytoma from the posterior third ventricle

Central neurocytoma is a rare benign tumor that most commonly arises within the ventricular system of young adults. Its occurrence in the posterior third ventricle is one of the least reported presentations. These tumors are usually treated by a combination of either biopsy or open surgical resection, often followed by radiation (Gamma knife or Novalis) with or without chemotherapy. A 37-year-old woman with a posterior third ventricle neurocytoma presented with acute signs of aqueductal stenosis. The patient underwent endoscopic assisted gross total resection of the tumor with the aid of intraoperative laser followed by standard third ventriculostomy; no further treatment was required. The patient did not develop any subsequent neurological deficit. A 36-month follow-up was still consistent with a normal neurological examination. Serial post-operative MRIs show neither residual nor recurrent tumor. Thus, posterior third ventricle central neurocytomas are relatively benign tumors that can be successfully removed using a minimally invasive approach, thereby avoiding both the morbidity related to conventional open craniotomy and the potential toxicity of any adjuvant treatment.

Progressive declines in neurocognitive function among survivors of hematopoietic stem cell transplantation for pediatric hematologic malignancies

Neurocognitive function of pediatric patients is of great concern after hematopoietic stem cell transplantation (HSCT). We evaluated the neurocognitive function of pediatric patients pre-HSCT, 1, 3, and 5 years post-HSCT. All patients had a hematologic malignancy and received therapy to their central nervous system. Healthy siblings were tested as a comparison group. Pediatric patients with a hematologic malignancy did not have a significant decrease in their cognitive function before HSCT compared with their siblings except in areas of academic achievement. Our study population had significant declines in visual motor skills and memory test scores within the first year post-HSCT. By 3 years post-HSCT, there was an improvement in the visual motor development scores and memory scores, but there were new deficits in verbal skills. By 5 years post-HSCT, there were progressive declines in verbal skills (P=0.005), performance skills (0.04), and new deficits seen in long-term verbal memory scores (0.04). On the basis of the raw scores, most of these tests showed that patients had an inability to acquire new skills at a rate comparable to their age-matched healthy peers. However, long-term memory scores showed definite declines. The greatest decline in neurocognitive function occurred in those patients who received cranial irradiation either as part of their initial therapy or as part of their HSCT conditioning. Pediatric patients who received HSCT for hematologic malignancies have neurocognitive deficiencies that are both acute and chronic. Although some patients have acute deficits that appear and improve over time, other patients have progressive declines in neurocognitive function that are chronic.

Radiation-induced changes in normal-appearing white matter in patients with cerebral tumors: a diffusion tensor imaging study

PURPOSE

To quantify the radiation-induced changes in normal-appearing white matter before, during, and after radiotherapy (RT) in cerebral tumor patients.

METHODS AND MATERIALS

Twenty-five patients with low-grade glioma, high-grade glioma, or benign tumor treated with RT were studied using diffusion tensor magnetic resonance imaging. The biologically corrected doses ranged from 50 to 81 Gy. The temporal changes were assessed before, during, and to 45 weeks after the start of RT. The mean diffusivity of water (<D>), fractional anisotropy of diffusion, diffusivity perpendicular (lambdaperpendicular) and parallel (lambda||) to white matter fibers were calculated in normal-appearing genu and splenium of the corpus callosum.

RESULTS

In the genu and splenium, fractional anisotropy decreased and <D>, lambda||, lambdaperpendicular increased linearly and significantly with time (p<0.01). At 45 weeks after the start of RT, lambdaperpendicular had increased approximately 30% in the genu and splenium, and lambda|| had increased 5% in the genu and 9% in the splenium, suggesting that demyelination is predominant. The increases in lambdaperpendicular and lambda|| were dose dependent, starting at 3 weeks and continuing to 32 weeks from the start of RT. The dose-dependent increase in lambdaperpendicular and lambda|| was not sustained after 32 weeks, indicating the transition from focal to diffuse effects.

CONCLUSION

The acute and subacute changes in normal-appearing white matter fibers indicate radiation-induced demyelination and mild structural degradation of axonal fibers. The structural changes after RT are progressive, with early dose-dependent demyelination and subsequent diffuse dose-independent demyelination and mild axonal degradation. Diffusion tensor magnetic resonance imaging is potentially a biomarker for the assessment of radiation-induced white matter injury.

Reversible CSF cyst related to a functioning ventriculo-peritoneal shunt

Although the occurrence of CSF oedema and cyst has been described in presence of a blocked ventriculoperitoneal shunt, especially distal end block, its occurrence in presence of a well functioning shunt has not been described so far. We report a case where a 51-year old lady developed an insidious onset and gradually progressive CSF cyst without any clinical or radiological feature of shunt block over a period of about 2 years. The changes started about 6 months after a course of radiation therapy for an extensive residual supra and infratentorial meningioma. Following surgery, where the cyst was punctured and a new ventricular catheter was inserted, despite well functioning upper and lower end, the cyst gradually disappeared. We review the literature and hypothesize that the radiation-induced changes were responsible for initiation and progression of the cyst.

Late magnetic resonance imaging features of leukoencephalopathy in children with central nervous system tumours following high-dose methotrexate and neuraxis radiation therapy

High-dose methotrexate (HDMTX) is used increasingly to treat children with central nervous system (CNS) tumours. Although the neuro-imaging features of leukoencephalopathy associated with systemic or intrathecal methotrexate administered after cranial radiation have been well described, the extent to which the sequencing of HDMTX prior to cranial radiation in infants and children predisposes to late neuroradiological features of leukoencephalopathy is unknown. This report describes the National Cancer Institute (NCI) toxicity grade of leukoencephalopathy based on magnetic resonance imaging (MRI) findings in all patients who survived 4 or more years after treatment on an earlier phase II study. These patients, with newly diagnosed CNS embryonal tumours, were in the age range 3.5-14.2 years (median 6.9 years) at diagnosis, and received four courses of pre-irradiation combination chemotherapy, including HDMTX 8 g/m(2). Following completion of the 'up-front' phase II study, all patients received conventionally fractionated whole brain doses of 36-50.4 Gy. The radiation dose and treatment volumes were determined individually according to the primary tumour location and results of extent of disease evaluations. The most recent MRI brain scans, obtained 4.0-10.5 years (median 6.5 years) after radiation therapy and comprising a minimum of T1, T1 following gadolinium and T2 sequences, were reviewed centrally to assess the neuroradiological grade of leukoencephalopathy, based on the NCI Common Terminology Criteria for Adverse Events, v3.0. Grade I changes (mild increase in subarachnoid space, and/or mild ventriculomegaly, and/or small/focal T2 hyperintensities) were evident in 8 of the 12 patients and grade II changes (moderate increase in subarachnoid space and/or moderate ventriculomegaly, and/or focal T2 hyperintensities extending to the centrum ovale) were found in the remaining 4. In conclusion, treatment with multiple courses of HDMTX prior to 36-50.4 Gy cranial radiation did not result in moderate to severe MRI features of leukoencephalopathy. Future studies in paediatric neuro-oncology patients, involving HDMTX combined with prospective neuropsychological evaluations appear justified.

Myelopathy due to intrathecal chemotherapy: report of six cases

Intrathecal chemotherapy and systemic chemotherapy are used for both prophylaxis and treatment of central nervous system disease in hematologic malignancies. However, intrathecal treatment has some adverse effects, such as arachnoiditis, progressive myelopathy, and leukoencephalopathy. The authors describe six children in whom myelopathy and adhesive arachnoiditis developed after administration of intrathecal chemotherapy including methotrexate, cytosine arabinoside, and prednisolone. Urinary retention and incontinence, the main presenting complaints in all patients, developed within 12 hours after intrathecal therapy and spontaneously resolved within 7 days. Two patients were unable to walk. In these two, weakness in the lower extremities gradually recovered by 1 month but urinary incontinence did not improve. None of the children had sensory loss. On follow-up periodic recurrent urinary tract infection was noted in four patients. MRI findings corresponded to arachnoiditis. No response was recorded on tibial nerve somatosensory evoked potentials in all patients. Intrathecal chemotherapy, especially methotrexate, can cause spinal cord dysfunction in children with acute lymphoblastic leukemia and non-Hodgkin's lymphoma. Arachnoiditis should be kept in mind as a causative factor in recurrent urinary tract infection in patients receiving intrathecal chemotherapy.

Intrinsic tectal low grade astrocytomas: is surgical removal an alternative treatment? Long-term outcome of eight cases

Low-grade gliomas arising in dorsal midbrain in children and young patients usually present few neurological symptoms and findings, and patients´ management is controversial. Some authors propose only clinical observation until the patient present signs of increased intracranial pressure when a shunt with or without biopsy, is inserted; others recommend radiotherapy after stereotactic or open biopsy. Microsurgical total removal of tumor may be curative. We present a retrospective analysis of eight patients (mean age 16.6 ±11.5 years-old) with low-grade astrocytoma of the tectal region operated on using an infratentorial/ supracerebellar approach between 1981 and 2002. All patients presented hydrocephalus and had a shunt insertion before surgical resection of the lesion. The tumour could be totally resected in seven patients. In one case radical removal was not possible due to infiltrative pattern of the lesion. Postoperative radiotherapy was performed in two cases, one patient at the beginning of this series and in the case with infiltrative tumor. This patient presented progressive tumor growth and died five years after surgery. No recurrence occurred after total removal. Post-surgical follow-up time ranged from 2 1/2 to 22 1/2 years (mean 9.9 ± 5.9 years). Radical microsurgical removal of non invasive tumors is possible without mortality or significant morbidity. It may be curative and should remain as an alternative to be discussed with the patient.

Neuroimaging-detected late transient treatment-induced lesions in pediatric patients with brain tumors

OBJECT

After the resection of brain tumors in pediatric patients, it can be difficult to differentiate recurrent tumor from treatment effects. Although late-delayed reactions are thought to be permanent, in this study the authors sought to characterize transient brain lesions (TBLs) in the late-delayed period that completely resolved without imaging or neurological sequelae.

METHODS

In a retrospective review of an institutional neuroimaging brain tumor database, 11 patients were identified who met the imaging criteria (transient T2-weighted hyperintense enhancing lesions outside of the tumor bed, which occurred after radiation and/or chemotherapy) and had undergone three-dimensional dosimetry; their radiographic, clinical, and radiation-dosimetry results were analyzed. In the 11 patients who had been treated with multiple protocols 17 loci of abnormality, including 43 discrete, asymptomatic TBLs, were detected. The median TBL diameter was 1 cm or smaller, without mass effect or necrosis, and occurred 10 months after radiation therapy, 11 months after chemotherapy, resolved by 3 months, and occurred within the high-dose radiation treatment volume (median 55.8 Gy). The findings from extended follow up revealed the development of additional permanent complications of radiation therapy within the radiation port in five of the 11 patients.

CONCLUSIONS

A benign form of treatment-induced brain injury in children, TBLs should be treated using short-interval follow up. When these lesions are identified as a result of their characteristic imaging features, location, and temporal course, TBLs may be clearly distinguished from recurrent tumor or radiation necrosis and do not require biopsy. Further studies are needed to determine whether patients with TBLs are at an increased risk of developing more severe treatment-related brain injury.

White Matter Lesions Detected by Magnetic Resonance Imaging After Radiotherapy and High-Dose Chemotherapy in Children With Medulloblastoma or Primitive Neuroectodermal Tumor

Purpose

White matter lesions (WMLs) have been described as a delayed effect of cranial irradiation in children with brain tumors, or a transient subacute effect characterized by an intralesional or perilesional reaction. We report the occurrence of subacute WMLs detected by magnetic resonance imaging (MRI) in children treated for medulloblastoma or primitive neuroectodermal tumor (PNET) and document the associated clinical, radiologic, and neurocognitive findings.

Patients and Methods

Among 134 patients with medulloblastoma or supratentorial PNET treated prospectively with risk-adjusted craniospinal irradiation and conformal boost to the tumor bed, followed by four high-dose chemotherapy (HDC) cycles with stem-cell rescue, 22 developed WMLs on T1-weighted imaging with and without contrast and/or T2-weighted imaging on MRI. Patients had ≥ 12 months of follow-up. Neurocognitive assessments included intelligence quotient (IQ) tests and tests of academic achievement.

Results

Twenty-two patients developed WMLs at a median of 7.8 months after starting therapy (range, 1.9 to 13.0 months). Lesions were predominantly in the pons (n = 8) and cerebellum (n = 6). Sixteen patients (73%) had WML resolution at a median of 6.2 months (range, 1.68 to 23.5 months) after onset; two patients developed necrosis and atrophy. Three developed persistent neurologic deficits. Cumulative incidence of WMLs at 1 year was 15% ± 3%. Patients with WMLs had a significant decline in estimated IQ (−2.5 per year; P = .03) and math (−4.5 per year; P = .003) scores.

Conclusion

WMLs in medulloblastoma or PNET patients treated with conformal radiotherapy and HDC are typically transient and asymptomatic, and may mimic early tumor recurrence. A minority of patients with WMLs develop permanent neurologic deficits and imaging changes. Overall, the presence of WMLs is associated with greater neurocognitive decline.

Radiation-induced brain disorders in patients with pituitary tumours

Radiation-induced brain disorders (RIBD) are uncommon and they are grave sequelae of conventional radiotherapy. In the present report, we describe the clinical spectrum of RIBD in 11 patients who received post-surgery conventional megavoltage irradiation for residual pituitary tumours. Of these 11 patients (nine men, two women), seven had been treated for non-functioning pituitary tumours and four for somatotropinomas. At the time of irradiation the age of these patients ranged from 30 to 59 years (mean, 39.4 +/- 8.3; median, 36) with a follow-up period of 6-96 months (mean, 18.3 +/- 26.4; median, 11). The dose of radiation ranged from 45 to 90 Gy (mean, 51.3 +/- 13.4; median, 45), which was given in 15-30 fractions (mean, 18.6 +/- 5.0; median, 15) with 2.8 +/- 0.3 Gy (median, 3) per fraction. The biological effective dose calculated for late complications in these patients ranged from 78.7 to 180 Gy (mean, 99.1 +/- 27.5; median, 90). The lag time between tumour irradiation and the onset of symptoms ranged from 6 to 168 months (mean, 46.3 +/- 57.0; median, 57). The clinical spectrum of RIBD included new-onset visual abnormalities in five, cerebral radionecrosis in the form of altered sensorium in four, generalized seizures in four, cognitive dysfunction in five, dementia in three and motor deficits in two patients. Magnetic resonance imaging (MRI)/CT of the brain was suggestive of radionecrosis in eight, cerebral oedema in three, cerebral atrophy in two and second neoplasia in one patient. Associated hormone deficiencies at presentation were hypogonadism in eight, hypoadrenalism in six, hypothyroidism in four and diabetes insipidus in one patient. Autopsy in two patients showed primitive neuroectodermal tumour (PNET) and brainstem radionecrosis in one, and a cystic lesion in the left frontal lobe following radionecrosis in the other. We conclude that RIBD have distinctive but varying clinical and radiological presentations. Diabetes insipidus and PNET as a second neoplastic disorder in adults following pituitary irradiation have not been reported previously.

Cerebral glucose metabolism in long-term survivors of childhood primary brain tumors treated with surgery and radiotherapy

Delayed structural cerebral sequelae has been reported following cranial radiation therapy (CRT) to children with primary brain tumors, but little is known about potential functional changes. Twenty-four patients were included, diagnosed and treated at a median age of 11 years, and examined after a median recurrence free survival of 16 years by MRI and Positron Emission Tomography using the glucose analog 2-18F-fluoro-2-deoxy-D-glucose (18FDG). Three patients were not analyzed further due to diffuse cerebral atrophy, which might be related to previous hydrocephalus. Twenty-one patients were evaluable and regional cerebral metabolic rate for glucose (rCMRglc) was estimated in nontumoral brain regions in 12 patients treated with surgery alone and 9 patients treated with both surgery and CRT. Furthermore 10 normal controls matched for age at examination were included. Patients treated with both surgery and CRT had a general decreased rCMRglc compared to normal controls and patients treated with surgery alone, significantly (p < 0.05) in 5 of 11 regions of interest. No difference was found in rCMRglc between normal controls and patients treated with surgery alone. We conclude that there is a general reduction in rCMRglc in long-term recurrence free survivors of childhood primary brain tumors treated with CRT in high doses (44-56 Gy).

Results of three-dimensional stereotactically-guided radiotherapy in recurrent medulloblastoma

PURPOSE

To evaluate survival rates and side effects after stereotactically-guided radiotherapy (SRT) in patients with recurrent medulloblastoma of the brain.

METHODS AND MATERIALS

Between 1992 and 2000, 20 patients with 29 radiological manifestations were treated with fractionated SRT (n = 21) or radiosurgery (n = 8). Median age was 16 years with 6 patients < or = 14 years. All patients had prior cranio-spinal radiotherapy plus boost to the posterior fossa with a total dose of 54 Gy. Time to recurrence was 33 months mean. Eighteen of the 29 lesions were located within the boost volume. Chemotherapy was given according to current international study protocols (HIT) in all patients. Mean total dose for re-irradiation was 24 Gy for fractionated stereotactically-guided radiotherapy, and 15 Gy for radiosurgery. Mean follow-up was 88.5 months.

RESULTS

Overall local control was 89.7%. Thirteen recurrences showed partial or complete response in CT/MR-imaging, 13 showed stable disease. Local tumor progression was seen 5 months mean after radiotherapy in three cases. A multifocal intracranial progression was seen in 9 patients, 5 patients developed additional spinal metastases. Thirteen patients died with disseminated cranio-spinal progression, after 72.6 months median. No late toxicity > CTC II(o) especially no brain radionecrosis was seen after radiotherapy.

CONCLUSION

SRT is effective and safe in the treatment of recurrent medulloblastoma to improve local control without evident side effects. The main problem remains the control of subclinical cranio-spinal dissemination.

Effect of therapeutic ionizing radiation on the human brain

We test a hypothesis that fractionated radiation therapy within a therapeutic dose range is associated with a dose-related change in normal brain, detectable by quantitative magnetic resonance imaging. A total of 33 patients were examined by quantitative magnetic resonance imaging to measure brain tissue spin-lattice relaxation time (T1) before treatment, and at various times during and after radiation therapy. A T1 map was generated at each time point, and radiation therapy isodose contours were superimposed on the corresponding segmented T1 map. Changes in white matter and gray matter T1 were analyzed as a function of radiation therapy dose and time since treatment, controlling for patient age and tumor site. In white matter, a dose level of more than 20 Gy was associated with a dose-dependent decrease in T1 over time, which became significant 6 months after treatment. There was no significant change in T1 of gray matter over time, at radiation therapy doses of less than 60 Gy. However, GM in close proximity to the tumor had a lower T1 before therapy. Our results represent the first radiation dose-response data derived from pediatric brain in vivo. These findings confirm that white matter is more vulnerable to radiation-induced change than is gray matter, and suggest that T1 mapping is sensitive to radiation-related changes over a broad dose range (20 to 60 Gy). Human white matter T1 is not sensitive to radiation therapy of less than 20 Gy, and gray matter T1 is unchanged over the dose range used to treat human brain tumor. The reduction of gray matter T1 near the tumor could result from compression of cortical parenchyma near the growing tumor mass, or from tumor cell invasion directly into the parenchyma. If brain T1 is a surrogate for radiation effect, reducing the volume of normal white matter receiving more than 20 Gy could be an important treatment planning goal.

Radiosurgery for the treatment of recurrent central neurocytomas

OBJECTIVE

Central neurocytomas are benign neoplasms with neuronal differentiation typically located in the lateral ventricles of young adults. Although the treatment of choice is complete surgical excision, patients may experience local recurrence. Adjuvant therapy for patients with residual or recurrent tumor has included reoperation, radiotherapy, or chemotherapy. To avoid the side effects of conventional radiotherapy in young patients, we present a series of patients with clear evidence of tumor progression who were treated with gamma knife radiosurgery.

METHODS

Four patients (ages 20-49 yr; mean, 28 yr) who presented with an intraventricular mass on magnetic resonance imaging scans and underwent craniotomy for tumor resection were reviewed retrospectively. Histopathological analysis confirmed central neurocytoma in all cases. Each patient was followed up clinically and radiographically with serial magnetic resonance imaging. When radiographic signs of tumor progression were evident, patients were treated with radiosurgery.

RESULTS

Complete radiographic tumor resection was achieved in all patients. There were no major postoperative complications. Local tumor progression was detected on magnetic resonance imaging scans 9 to 25 months after surgery (median, 17.5 mo). All patients achieved complete response to radiosurgery with reduction in tumor size. There have been no complications from radiosurgery. Follow-up ranged from 12 to 28 months (mean, 16.5 mo) after radiosurgery, and from 24 to 84 months (mean, 54.5 mo) after initial presentation.

CONCLUSION

Radiosurgery with the gamma knife unit provides safe and effective adjuvant therapy after surgical resection of central neurocytomas. Radiosurgery may eliminate the need for reoperation and avoid the possible long-term side effects from conventional radiotherapy in young patients.

Effect of ionizing radiation on the human brain: white matter and gray matter T1 in pediatric brain tumor patients treated with conformal radiation therapy

OBJECTIVE

To test a hypothesis that fractionated radiation therapy (RT) to less than 60 Gy is associated with a dose-related change in the spin-lattice relaxation time (T1) of normal brain tissue, and that such changes are detectable by quantitative MRI (qMRI).

METHODS

Each of 21 patients received a qMRI examination before treatment, and at several time points during and after RT. A map of brain T1 was calculated and segmented into white matter and gray matter at each time point. The RT isodose contours were then superimposed upon the T1 map, and changes in brain tissue T1 were analyzed as a function of radiation dose and time following treatment. We used a mixed-model analysis to analyze the longitudinal trend in brain T1 from the start of RT to 1 year later. Predictive factors evaluated included patient age and clinical variables, such as RT dose, time since treatment, and the use of an imaging contrast agent.

RESULTS

In white matter (WM), a dose level of greater than 20 Gy was associated with a dose-dependent decrease in T1 over time, which became significant about 3 months following treatment. In gray matter (GM), there was no significant change in T1 over time, as a function of RT doses < 60 Gy. However, GM in close proximity to the tumor had an inherently lower T1 before therapy. Neither use of a contrast agent nor a combination of chemotherapy plus steroids had a significant effect on brain T1.

CONCLUSION

Results suggest that T1 mapping may be sensitive to radiation-related changes in human brain tissue T1. WM T1 appears to be unaffected by RT at doses less than approximately 20 Gy; GM T1 does not change at doses less than 60 Gy. However, tumor appears to have an effect upon adjacent GM, even before treatment. Conformal RT may offer a substantial benefit to the patient, by minimizing the volume of normal brain exposed to greater than 20 Gy.

Acute neurotoxicity in children with B-lineage acute lymphoblastic leukemia (B-ALL) treated with intermediate risk protocols

BACKGROUND

This study describes the incidence of acute neurotoxicity (NT) in children with B-lineage acute lymphoblastic leukemia (ALL) treated with three intermediate risk protocols that differ in the intensity of central nervous system (CNS) "prophylaxis. "

PROCEDURE

A total of 122 patients (64 boys; median age 5.3 years) with B-lineage ALL without CNS leukemia diagnosed between February 1987 and December 1997 were enrolled in the intermediate risk (IR) protocols: Associazione Italiana di Ematologia ed Oncologia Pediatrica (AIEOP)-ALL 87 (n = 33), 91 (n = 51), and 95 (n = 38). Presymptomatic CNS therapy consisted of intrathecal methotrexate (six doses) and cranial irradiation (18 Gy) in the IR AIEOP 87 study, and extended triple intrathecal therapy with methotrexate, cytarabine, and prednisone depending on age in the IR AIEOP-ALL 91 and 95 protocols (20 and 17 total doses, respectively). World Health Organization (WHO) grade 4 acute neurotoxicity criteria were employed. Patients with neurologic symptoms, in addition to physical examination, underwent EEG, computed tomography (CT) and/or magnetic resonance imaging (MRI), and lumbar puncture to exclude CNS leukemia and infection.

RESULTS

Acute NT was not reported in AIEOP-ALL 87 treated patients, but we observed acute NT in 3 out of 51 (5.8%) AIEOP-ALL 91 patients, and in 7 out of 38 (18.4%) AIEOP-ALL 95 patients.

CONCLUSIONS

There was an increased incidence of acute NT in our patients with ALL treated with current intermediate risk protocols. The intensification of treatment, however, bettered event free survival (EFS) to 58%, 72% and 85% in IR AIEOP 87, 91 and 95 studies, respectively.

Anterior lumbosacral radiculopathy after intrathecal methotrexate treatment

Intrathecal chemotherapy with methotrexate or cytosine arabinoside is the standard approach to prophylaxis and treatment of central nervous system leukemia in children. Progressive paraplegia, one of the devastating neurologic complications related to this mode of treatment, has been attributed to spinal cord toxicity. Reported are three children who developed progressive paraparesis after intrathecal methotrexate administration followed by complete or partial recovery. Gadolinium enhancement of anterior lumbosacral spinal nerve roots was demonstrated in all three patients, and an elevation of cerebrospinal fluid immunoglobulin G synthesis was evident in two patients with more severe symptoms. The clinical data suggest that anterior lumbosacral radiculopathy is also a type of neurologic complication associated with intrathecal methotrexate treatment.

Chemotherapy for pancreatic cancer: a neuroimaging clinicopathologic correlation

This 52-year-old male without a significant medical history was receiving chemotherapy with diethylnorspermine (DENSPM), a polyamine analogue, for a partially resected pancreatic adenocarcinoma. Ten months after his initial diagnosis, he was admitted to an outside hospital for evaluation of altered mental status. Over the course of the next few days the patient developed progressive neurologic signs and symptoms including lethargy, tonic deviation of his eyes to the left, asymmetic pupils, and right-sided decerebrate posturing elicited by painful stimuli. Neuroimaging studies revealed multiple lesions scattered in the periventricular white matter, thalamus, midbrain pons, and cerebellar peduncles. The clinical and neuroimaging differential diagnoses are discussed, and postmortem neuropathologic correlation is presented.

Intravenous methotrexate as initial treatment for primary central nervous system lymphoma: response to therapy and quality of life of patients

In anticipation of a consortium study of methotrexate (MTX) therapy provided to patients with primary central nervous system lymphoma (PCNSL) we have provided intravenous MTX without irradiation therapy to 31 nonimmunosuppressed individuals. Twenty (65%) achieved complete response and 11 (35%) partial response to therapy. For the 31 patients the median survival was 30.43 months with an actuarial median follow-up time of 30.69 months. The 2+ year survival was 63% for all patients and 90% for complete responders. Of 375 drug cycles, grade 3 leukopenia was identified in 3 cycles, mucositis in 6 cycles and delayed drug clearance in 47 cycles. Recurrences included brain (9/20) and/or spinal fluid (2/20). The median Karnofsky scale improved from 40 (10-80) prior to therapy to 90 after treatment. Eleven patients, in complete response for a median of 22+ months after diagnosis were evaluated using 4 instruments that assess Quality of Life Functional Assessment of Cancer Therapy - Brain (FACT-BR) modified, Symptom Questionnaire, Social Adjustment Scale-Self-Report and Problem Solving Inventory. Their psychosocial adjustment, well-being and stress coping abilities were comparable to the normative groups. Further there was no evidence of any MTX-induced, Magnetic Resonance Imaging (MRI)-detected encephalopathy in these individuals and there was preservation of clinical cognition and memory. We conclude that therapy with MTX, without radiation can be used in PCNSL patients without limitations of age or pretreatment Karnofsky scores. Further rates of response and median survival approach those of therapies using multiple drugs and radiation, but with a less likely risk of dementia.

[Combined chemoradiotherapy of tumors in the child]

The high chemosensitivity of pediatric tumors along with their natural propensity for an early distant dissemination have stimulated the interest for chemo-radiation combinations in children since the mid 50s. Following the early experiments in nephroblastomas on the interaction of Actinomycin-D and radiotherapy, multiple national and international studies have been conducted since the mid 70s with considerable success: nowadays most pediatric tumors enjoy a long term survival in excess of 70%. Like their adult counterparts, these associations aim to induce an early control of the primary tumor and distant spreading (spatial cooperation) but also, more specifically in children, to limit the toxicity on normal tissues when treatment intensity can be further reduced. The association of an initial chemotherapy followed by local radiation at a dose and in a volume adapted to the response to chemotherapy along with associated prognostic factors has become widely tested in national and international studies conducted in Hodgkin's disease, Ewing's sarcoma, medulloblastomas, and brain tumors in the very young. Conversely, concomitant associations have remained limited to high-risk subgroups (parameningeal rhabdomyosarcomas for example) due to their potential hazards.

[Late effects of ionizing radiations on central nervous system, spinal cord and peripheral nerves]

Despite the lack of characteristic features, demyelination is the dominant feature of radiation induced late effects observed in cerebral nervous system and spinal cord. Acute, subacute and chronic changes are described in terms of pathological, clinical and radiological observations. Brain necrosis in adults is rarely noted below 60 Gy in conventional fractionation, while imaging changes are observed with lower doses. The most widely observed dose limit for the spinal cord is 45 Gy, in the absence of dose modifying chemotherapy. Tumor progression may be hard to distinguish from radiochemotherapy effects. The potential protective role of hyperfractionation is not yet clearly established. Peripheral nerves late effects, although rare, are described.

Application of proton chemical shift imaging in monitoring of gamma knife radiosurgery on brain tumors

Our objective was to assess proton chemical shift imaging for potential clinical application in monitoring response to gamma knife radiosurgery. Twenty-five proton chemical shift imaging studies and conventional magnetic resonance images were performed on six patients with intracranial tumors. The peak areas of N-acetylaspartate, choline-containing compounds (Cho), creatine, and lipids were calculated and normalized to N-acetylaspartate in the contralateral hemisphere. The spectra from the lesion before treatment showed a relatively high Cho peak, reported as a characteristic spectrum of tumors. Tumor size and Cho level after radiosurgery did not increase except in two cases. In these cases, radiation necrosis was observed with elevated Cho and a mobile lipid peak. Stable or decreased Cho seems to suggest a loss of tumor viability, and changes in Cho indicate the effectiveness of radiosurgery. Increasing Cho and the appearance of the mobile lipid peak may distinguish radiation necrosis from recurrent tumors, which cannot be distinguished by magnetic resonance imaging.

Dose-response tolerance of the visual pathways and cranial nerves of the cavernous sinus to stereotactic radiosurgery

As the number of patients treated with stereotactic radiosurgery increases, it becomes particularly important to define with precision adverse effects on distinct structures of the nervous system.

OBJECT

This study was designed to assess the dose-response tolerance of the visual pathways and cranial nerves after exposure of the cavernous sinus to radiation.

METHODS

A total of 66 sites in the visual system and 210 cranial nerves of the middle cranial fossa were investigated in 50 patients who had undergone gamma knife treatment for benign skull base tumors. The mean follow-up period was 40 months (range 24-60 months). Follow-up examinations consisted of neurological, neuroradiological, and neuroophthalmological evaluations. The actuarial incidence of optic neuropathy was zero for patients who received a radiation dose of less than 10 Gy, 26.7% for patients receiving a dose in the range of 10 to less than 15 Gy, and 77.8% for those who received doses of 15 Gy or more (p < 0.0001). Previously impaired vision improved in 25.8% and was unchanged in 51.5% of patients. No sign of neuropathy was seen in patients whose cranial nerves of the cavernous sinus received radiation doses of between 5 and 30 Gy. Because tumor control appeared to have been achieved in 98% of the patients, the deterioration in visual function cannot be attributed to tumor progression.

CONCLUSIONS

The structures of the visual pathways (the optic nerve, chiasm, and tract) exhibit a much higher sensitivity to single-fraction radiation than other cranial nerves, and their particular dose-response characteristics can be defined. In contrast, the oculomotor and trigeminal nerves have a much higher dose tolerance.

Short-term CT and MR changes in brain tumors following 125I interstitial irradiation

PURPOSE

The study was undertaken to assess characteristic short-term CT and MR changes in brain tumors following 125I interstitial irradiation.

METHOD

Sixteen patients were included who had both CT and MR control examinations at regular intervals over a period of 18 months following treatment. Two groups were distinguished: low grade tumors (11 cases) and high grade malignancies (5 patients). 125I seeds were used as temporary implants. The cumulative dose was 50-60 Gy.

RESULTS

In some patients of both groups, a low attenuation spheric structure with a contrast-medium-enhanced ring and a diameter of 6-8 mm was observed. There was no edema around the structure, which represents a zone of tissue necrosis at the site of the temporary 125I implant. Tumors in both groups were completely destroyed, some decreased in size, and others were unchanged. Pseudotumor necrosis with accompanying edema occurred in two patients with low grade astrocytoma, the diameter of which was > 4 cm.

CONCLUSION

The behavior of cerebral tumors and their appearance on CT and MR images after interstitial irradiation seem to be variable. Decrease in tumor size may take place at different intervals after therapy. Brachytherapy of tumors with a diameter of > 4 cm may produce space-occupying radionecrosis.

Magnetic resonance imaging changes after stereotactic radiation therapy for childhood low grade astrocytoma

BACKGROUND

Stereotactic radiotherapy (SRT) is fractionated radiotherapy delivered under stereotactic guidance to produce highly focal and precise therapy. We studied the incidence of imaging changes that can mimic tumor progression after completion of SRT for childhood low grade astrocytoma.

METHODS

Between June 1992 and September 1994, we prospectively treated 28 children with low grade astrocytomas with SRT. The patients ranged in age from 2 to 22 years (median: 10 yrs) and none had received prior radiation therapy or radiosurgery. Routine fractionation was employed (180-200 centigray[cGy]) to a total dose of 5220-6000 cGy over 5 to 6 weeks. All of the patients underwent initial and follow-up magnetic resonance imaging (MRI) according to protocol.

RESULTS

Median clinical follow-up for the 28 patients was 24 months (range, 5-32 mos) with a median radiographic follow-up of 15 months (range, 3-26 mos). Fifteen patients had reduction in tumor size, one patient had stable disease. Twelve patients (43%) developed increased size of the lesion, increased signal intensity or enhancement, cysts or cavitations, and an increase in edema or mass effect on follow-up MRI. Most of these changes occurred between 9 and 12 months after the start of SRT and resolved or decreased by 15 to 21 months. All but one patient had normal or stable neurologic examinations.

CONCLUSIONS

Treatment-related MRI changes are common after conventionally fractionated schedules using stereotactic radiation techniques for patients with low grade astrocytomas. These changes can be distinguished from tumor progression by their transient nature as well as the general absence of clinical symptoms.

Tirilazad does not protect rat brain from brachytherapy-induced injury

BACKGROUND

Acute and chronic brain injury are common sequelae of high-dose focused radiation, as in radiosurgery and brachytherapy. Development of protectors of radiation injury, which would work in brain but not in tumor, would help enhance the therapeutic ratio of focused-radiation therapy.

METHODS

Radiation protection by a clinically available 21-aminosteroid, Tirilazad, was studied in a rat brain brachytherapy model, both in tumor and non-tumor bearing animals. For the tumor model, 9L Glioma/SF line cells were implanted stereotactically into the right frontal lobe of F-344 rats and grew to a sphere of 5.0-mm diameter after 12 days. Animals received a standard brachytherapy dose of 80 Gy to a 5.5-mm radius volume administered by a high-activity removable iodine-125 seed. Radiation damage was evaluated 24 hours after removal of the seeds in all animals and again at 3 months in non-tumor-bearing animals, by T1-weighted gadolinium-enhanced and T2-weighted magnetic resonance imaging (MRI) on a 1.5-T unit. Treated animals received Tirilazad 5 mg/kg intravenously 15 minutes prior to implant, 1 hour after implant, every 6 hours for the duration of the implant, and for 24 hours after removal of the seed. Control animals were administered vehicle only.

RESULTS

In both non-tumor-bearing and tumor-bearing rats, no difference in the volume of lesions on enhanced T1 or T2 MRI was seen between the Tirilazad-treated and control groups. In the non-tumor-bearing rats, volume of both T1 enhanced and T2 MRI lesions was significantly reduced at 3 months compared to the values at 24 hours.

CONCLUSIONS

In the present model, Tirilazad failed to reduce the volume of radiation brain injury from brachytherapy as seen on MRI, studied acutely in tumor-bearing and non-tumor-bearing animals and also at 3 months in non-tumor-bearing rats.

Magnetic resonance imaging and neurological evaluation after treatment with high-dose methotrexate for acute lymphocytic leukaemia in young children

This study evaluates the occurrence of permanent cerebral white matter changes and neurological abnormalities in children treated at a young age for acute lymphocytic leukaemia. Our pilot treatment protocol did not include central nervous system irradiation, but intrathecal methotrexate and high-dose methotrexate infusions followed by very intensive folinic acid rescue. We examined 12 children in complete remission and off therapy 18 months to 9.5 years after their last methotrexate infusion. They were below 5 years of age at diagnosis and therefore expected to be at special risk of neurotoxic sequelae. Cerebral magnetic resonance imaging in the 11 cases thus evaluated did not reveal white matter abnormalities or other signal changes as signs of permanent treatment-related sequelae. We did not observe any pathological clinical neurological findings likely due to methotrexate.

Minor changes on cranial MRI during treatment in children with acute lymphoblastic leukaemia

Cranial MRI was used to study treatment-related changes in children undergoing therapy for acute lymphoblastic leukaemia (ALL) or lymphoma. Nineteen children (18 with ALL, 1 with lymphoma) underwent MRI at the beginning of treatment and at intervals during it, to a total of 105 imaging studies and a minimum of 3 per case. Nine patients had finished all therapy, all received consolidation treatment. No patient had central nervous system (CNS) leukaemia at diagnosis or developed a CNS relapse. Mild treatment-related white matter changes were observed in only 2 patients after consolidation therapy with three 5 g/m2 pulses of intravenous methotrexate. Transient enlargement of the ventricles and cortical sulci was observed in 13 patients, always temporally related to steroid treatment. These preliminary data suggest that treatment-related white matter changes are rare and no routine MRI follow-up is needed during treatment in asymptomatic children after a baseline assessment.

Leukoencephalopathy in childhood hematopoietic neoplasm caused by moderate-dose methotrexate and prophylactic cranial radiotherapy--an MR analysis

PURPOSE

The main purpose of this study was to determine influential factors related to minor leukoencephalopathy (LEP) caused by moderate-dose methotrexate (MTX) and prophylactic cranial radiotherapy (CRT) in childhood hematopoietic malignancies. We also compared the incidence of LEP following this treatment to that reported in the literature following treatment with high-dose MTX alone.

METHODS AND MATERIALS

Thirty-eight pediatric patients of hematopoietic malignancies (37 acute lymphoblastic leukemias, 1 non-Hodgkin lymphoma) who were given CRT (18-24 Gy) as well as prophylactic intrathecal and per os MTX were studied for leukoencephalopathy by magnetic resonance (MR) imaging. All the patients were free from grave neuropsychiatric disturbances. The data were examined to elucidate the influential ones of five factors (patients' age, doses of intrathecal and per os MTX, dose of CRT, interval between treatment, and MR study) to develop LEP using multiple regression analysis. To compare the effect of moderate-dose MTX and prophylactic CRT on LEP to that of high-dose MTX alone, we conducted literature review.

RESULTS

Seven out of 38 patients (18%) developed LEP. From multiple regression analysis and partial correlation coefficients, the age and CRT dose seemed influential in the subsequent development of LEP. The incidence of LEP following treatment with moderate-dose MTX and prophylactic CRT appears to be less than that reported in the literature following treatment with intravenous high-dose MTX. However, even moderate-dose MTX in combination with CRT can result in a significant incidence of MR-detectable LEP, particularly in children 6 years of age or younger receiving 24 Gy.

CONCLUSION

Leukoencephalopathy was caused by moderate-dose MTX and prophylactic CRT in pediatric patients, probably less frequently than by high-dose MTX treatment alone. The influential factors were patient's age and CRT dose.

Quantitative magnetic resonance and isotopic imaging: early evaluation of radiation injury to the brain

PURPOSE

Using magnetic resonance (MR) and isotopic imaging to investigate the cerebral alterations after highdose single-fraction irradiation on a pig model. We assessed the nuclear magnetic resonance (NMR) relaxation times as early markers of radiation injury to the healthy brain.

METHODS AND MATERIALS

A total of 17 animals was studied; 15 irradiated and 2 unirradiated controls. Pigs were irradiated with a 12 MeV electron beam at a rate of 2 Gy/min. Ten animals received 40 Gy at the 90% isodose, five animals received 60 Gy, and two animals were unirradiated. The follow-up intervals ranged from 2 days to 6 months. T1-weighted scans, T2-weighted scans, and scintigrams were performed on all animals to study neurological abnormalities, cerebral blood flow, and blood-brain barrier (BBB) integrity. T1 and T2 relaxation times were measured in selected regions of interest (ROIs) within the irradiated and contralateral hemispheres. A ratio T1 after irradiation/T1 before irradiation, and a ratio T2 after irradiation/T2 before irradiation, were calculated, pooled for each dose group, and followed as a function of time after irradiation.

RESULTS

Scintigraphy visualized the brain perfusion defect and BBB disruption in all irradiated brains. The ratio T2 after irradiation/T2 before irradiation was proportional to the effective dose received. The T2 ratio kinetics could be analyzed in three phases:an immediate and transient phase, two long-lasting phases, which preceded compression of the irradiated lateral ventricle, and edema and necrosis at later stages of radiation injury, respectively. The magnetic resonance imaging (MRI) observations correlated well with histological analysis.

CONCLUSION

The results show that quantitative imaging is a sensitive in vivo method for early detection of cerebral radiation injury. The reliability and dose dependence of T2 relaxation time may offer new opportunities to detect and understand brain pathophysiology after high-dose single-fraction irradiation.

Radiation response of the central nervous system

This report reviews the anatomical, pathophysiological, and clinical aspects of radiation injury to the central nervous system (CNS). Despite the lack of pathognomonic characteristics for CNS radiation lesions, demyelination and malacia are consistently the dominant morphological features of radiation myelopathy. In addition, cerebral atrophy is commonly observed in patients with neurological deficits related to chemotherapy and radiation, and neurocognitive deficits are associated with diffuse white matter changes. Clinical and experimental dose-response information have been evaluated and summarized into specific recommendations for the spinal cord and brain. The common spinal cord dose limit of 45 Gy in 22 to 25 fractions is conservative and can be relaxed if respecting this limit materially reduces the probability of tumor control. It is suggested that the 5% incidence of radiation myelopathy probably lies between 57 and 61 Gy to the spinal cord in the absence of dose modifying chemotherapy. A clinically detectable length effect for the spinal cord has not been observed. The effects of chemotherapy and altered fractionation are also discussed. Brain necrosis in adults is rarely noted below 60 Gy in conventional fractionation, with imaging and clinical changes being observed generally only above 50 Gy. However, neurocognitive effects are observed at lower doses, especially in children. A more pronounced volume effect is believed to exist in the brain than in the spinal cord. Tumor progression may be hard to distinguish from radiation and chemotherapy effects. Diffuse white matter injury can be attributed to radiation and associated with neurological deficits, but leukoencephalopathy is rarely observed in the absence of chemotherapy. Subjective, objective, management, and analytic (SOMA) parameters related to radiation spinal cord and brain injury have been developed and presented on ordinal scales.

Follow-up of cognitive functioning in patients with small cell lung cancer

PURPOSE

Study of the course of possible treatment-related cognitive impairment in patients with small cell lung cancer.

METHODS AND MATERIALS

Thirty-two consecutive patients with small cell lung cancer underwent successive neurologic and neuropsychologic examinations until 5 months after prophylactic cranial irradiation, and in their pretherapeutic condition were compared to matched controls. Patients with brain metastases were excluded from this study.

RESULTS

Neurologic examination revealed central nervous system (CNS) abnormalities only in the 14 patients with brain metastases. In the remaining patients, neuropsychologic tests showed clear differences between the pretherapeutic performance of patients and that of matched controls (p < 0.001), but no significant deterioration either during or after therapy (0.1 < p < 0.8).

CONCLUSION

The difference between the pretherapeutic performance of patients and that of matched controls may indicate disease-related cognitive impairment. Within the observation period, no adverse effects of the used therapy were found. Our observations underline the importance of a pretherapeutic assessment in neurotoxicity research.

Multifocal inflammatory leukoencephalopathy associated with levamisole and 5-fluorouracil: case report

Levamisole and 5-fluorouracil have now become the standard chemotherapeutic regimen for patients with Stage III colon carcinoma. A case of multifocal inflammatory leukoencephalopathy secondary to levamisole alone or combination of levamisole and 5-fluorouracil is reported. Magnetic resonance imaging with gadolinium demonstrated multifocal contrast-enhancing frontal, parietal, occipital, and periventricular white matter lesions. A stereotactic biopsy revealed reactive gliosis and macrophage infiltration, without evidence of metastatic tumor. Despite continuation of 5-fluorouracil, resolution of contrast-enhancing lesions on magnetic resonance imaging without further neurological sequelae occurred when levamisole was stopped. The patient died with evidence of systemic metastasis 6 months later. Autopsy examination of the brain revealed multifocal demyelinating lesions, with no evidence of metastatic tumor. Immunoperoxidase studies of demyelinated lesions demonstrated infiltrating macrophages strongly positive for Class II antigens, interleukin-6, and interleukin-1 alpha. Surrounding astrocytes were positive for granulocyte macrophage colony-stimulating factor. Small numbers of perivascular T cells were present. This patient represents the first autopsy documented case of levamisole associated multifocal inflammatory leukoencephalopathy.