Large dose increment irradiation in treatment of cerebral metastases

Neurologic Changes Induced by Whole-Brain Synchrotron Microbeam Irradiation: 10-Month Behavioral and Veterinary Follow-Up

PURPOSE

Novel radiation therapy approaches have increased the therapeutic efficacy for malignant brain tumors over the past decades, but the balance between therapeutic gain and radiotoxicity remains a medical hardship. Synchrotron microbeam radiation therapy, an innovative technique, deposes extremely high (peak) doses in micron-wide, parallel microbeam paths, whereas the diffusing interbeam (valley) doses lie in the range of conventional radiation therapy doses. In this study, we evaluated normal tissue toxicity of whole-brain microbeam irradiation (MBI) versus that of a conventional hospital broad beam (hBB).

METHODS AND MATERIALS

Normal Fischer rats (n = 6-7/group) were irradiated with one of the two modalities, exposing the entire brain to MBI valley/peak doses of 0/0, 5/200, 10/400, 13/520, 17/680, or 25/1000 Gy or to hBB doses of 7, 10, 13, 17, or 25 Gy. Two additional groups of rats received an MBI valley dose of 10 Gy coupled with an hBB dose of 7 or 15 Gy (groups MBI17* and MBI25*). Behavioral parameters were evaluated for 10 months after irradiation combined with veterinary observations.

RESULTS

MBI peak doses of ≥680 Gy caused acute toxicity and death. Animals exposed to hBB or MBI dose-dependently gained less weight than controls; rats in the hBB25 and MBI25* groups died within 6 months after irradiation. Increasing doses of MBI caused hyperactivity but no other detectable behavioral alterations in our tests. Importantly, no health concerns were seen up to an MBI valley dose of 17 Gy.

CONCLUSIONS

While acute toxicity of microbeam exposures depends on very high peak doses, late toxicity mainly relates to delivery of high MBI valley doses. MBI seems to have a low impact on normal rat behavior, but further tests are warranted to fully explore this hypothesis. However, high peak and valley doses are well tolerated from a veterinary point of view. This normal tissue tolerance to whole-brain, high-dose MBI reveals a promising avenue for microbeam radiation therapy, that is, therapeutic applications of microbeams that are poised for translation to a clinical environment.

Dosimetric Impact of Lesion Number, Size, and Volume on Mean Brain Dose with Stereotactic Radiosurgery for Multiple Brain Metastases

We evaluated the effect of lesion number and volume for brain metastasis treated with SRS using GammaKnife^® ICON™ (GK) and CyberKnife^® M6™ (CK). Four sets of lesion sizes (<5 mm, 5-10 mm, >10-15 mm, and >15 mm) were contoured and prescribed a dose of 20 Gy/1 fraction. The number of lesions was increased until a threshold mean brain dose of 8 Gy was reached; then individually optimized to achieve maximum conformity. Across GK plans, mean brain dose was linearly proportional to the number of lesions and total GTV for all sizes. The numbers of lesions needed to reach this threshold for GK were 177, 57, 29, and 10 for each size group, respectively; corresponding total GTVs were 3.62 cc, 20.37 cc, 30.25 cc, and 57.96 cc, respectively. For CK, the threshold numbers of lesions were 135, 35, 18, and 8, with corresponding total GTVs of 2.32 cc, 12.09 cc, 18.24 cc, and 41.52 cc respectively. Mean brain dose increased linearly with number of lesions and total GTV while V8 Gy, V10 Gy, and V12 Gy showed quadratic correlations to the number of lesions and total GTV. Modern dedicated intracranial SRS systems allow for treatment of numerous brain metastases especially for ≤10 mm; clinical evidence to support this practice is critical to expansion in the clinic.

Identifying Topics and Evolutionary Trends of Literature on Brain Metastases Using Latent Dirichlet Allocation

Research on brain metastases kept innovating. We aimed to illustrate what topics the research focused on and how it varied in different periods of all the studies on brain metastases with topic modelling. We used the latent Dirichlet allocation model to analyse the titles and abstracts of 50,176 articles on brain metastases retrieved from Web of Science, Embase and MEDLINE. We further stratified the articles to find out the topic trends of different periods. Our study identified that a rising number of studies on brain metastases were published in recent decades at a higher rate than all cancer articles. Overall, the major themes focused on treatment and histopathology. Radiotherapy took over the first and third places in the top 20 topics. Since the 2010’s, increasing attention concerned about gene mutations. Targeted therapy was a popular topic of brain metastases research after 2020.

Supportive care for patients with brain metastases from lung cancer

Lung cancer is the most common cause of intracranial metastases (ICM). Metastases in the brain can result in a broad range of uncomfortable symptoms and significant morbidity secondary to neurological disability. Treatment options can range from surgical resection of solitary metastases to radiotherapy and more recently systemic targeted therapies and immunotherapy. Patient survival continues to improve with innovations made in treatments for this condition, but each of these treatments carry their own adverse effects that must be appropriately managed. These patients can benefit greatly from multidisciplinary care throughout the course of their disease. Clinicians involved in their care must be equipped with the ability to communicate skillfully and compassionately and set expectations for the road ahead, including symptoms, treatment plans, and prognosis. Involvement of a palliative care team can be very helpful, especially for patients who are nearing the terminal stages of the disease. Palliative care skills may be invaluable in the management of symptoms and can ease suffering for patients and their caregivers, thus allowing for maximum quality of life for as long as possible. End of life may bring its own complications and challenges; and opinion of an experienced and knowledgeable clinician can alleviate the pain and distress of the patient and also bring peace to the caregivers and loved ones.

Brain volume reduction after whole-brain radiotherapy: quantification and prognostic relevance

Background

Recent studies have questioned the value of adding whole-brain radiotherapy (WBRT) to stereotactic radiosurgery (SRS) for brain metastasis treatment. Neurotoxicity, including radiation-induced brain volume reduction, could be one reason why not all patients benefit from the addition of WBRT. In this study, we quantified brain volume reduction after WBRT and assessed its prognostic significance.

Methods

Brain volumes of 91 patients with cerebral metastases were measured during a 150-day period after commencing WBRT and were compared with their pretreatment volumes. The average daily relative change in brain volume of each patient, referred to as the "brain volume reduction rate," was calculated. Univariate and multivariate Cox regression analyses were performed to assess the prognostic significance of the brain volume reduction rate, as well as of 3 treatment-related and 9 pretreatment factors. A one-way analysis of variance was used to compare the brain volume reduction rate across recursive partitioning analysis (RPA) classes.

Results

On multivariate Cox regression analysis, the brain volume reduction rate was a significant predictor of overall survival after WBRT (P < 0.001), as well as the number of brain metastases (P = 0.002) and age (P = 0.008). Patients with a relatively favorable prognosis (RPA classes 1 and 2) experienced significantly less brain volume decrease after WBRT than patients with a poor prognosis (RPA class 3) (P = 0.001). There was no significant correlation between delivered radiation dose and brain volume reduction rate (P = 0.147).

Conclusion

In this retrospective study, a smaller decrease in brain volume after WBRT was an independent predictor of longer overall survival.

Clinical Results of Unconventional Fractionation Radiotherapy in Central Nervous System Tumors

Malignant brain tumors (primary and metastatic) are apparently resistant to most therapeutic efforts. Several randomized trials have provided evidence supporting the efficacy of radiation therapy. Attempts at improving the results of external beam radiotherapy include altered fractionation, radiation sensitizers and concomitant chemotherapy. In low-grade gliomas, all clinical studies with radiotherapy have employed conventional dose fractionation regimens. In high-grade gliomas, hypofractionation schedules represent effective palliative regimens in poor prognosis subsets of patients; short-term survival in these patients has not allowed to evaluate late toxicity. In tumors arising within the central nervous system, hyperfractionated irradiation exploits the differences in repair capacity between tumour and late responding normal tissues. It may allow for higher total dose and may result in increased tumor cell kill. Accelerated radiotherapy may reduce the repopulation of tumor cells between fractions. It may potentially improve tumor control for a given dose level, provided that there is no increase in late normal tissue injury. In supratentorial malignant gliomas, superiority of accelerated hyperfractionated over conventionally fractionated schedules was observed in a randomized trial; however, the gain in survival was less than 6 months. At present no other randomized trial supports the preferential choice for altered fractionation irradiation. Also in pediatric brainstem tumors there are no data to confirm the routine use of hyperfractionated irradiation, and significant late sequelae have been reported in the few long-term survivors. Shorter treatment courses with accelerated hyperfractionated radiotherapy may represent a useful alternative to conventional irradiation for the palliation of brain metastases. Different considerations have been proposed to explain this gap between theory and clinical data. Patients included in dose/effect studies are not stratified by prognostic factors and other treatment-related parameters. This observation precludes any definite conclusion about the relative role of conventional and of altered fractionation. New approaches are currently in progress. More prolonged radiation treatments, up to higher total doses, could delay time to tumor progression and improve survival in good prognosis subsets of patients; altered fractionation may be an effective therapeutic tool to achieve this goal.

Radiochirurgia con acceleratore lineare: 5 anni di esperienza clinica

Gli autori utilizzano una tecnica di radiochirurgia con acceleratore lineare dal 1982. La tecnica è basata su irradiazioni multiple ad archi intersecantisi focalizzate stereotassicamente su un bersaglio.

Dopo che una valutazione meccanica e dosimetrica ha dimostrato la validità della procedura, la tecnica è stata impiegata su un gruppo selezionato di pazienti. Dal novembre 1982 al marzo 1988 sono stati trattati 155 casi. Tra loro 72 erano affetti da malformazioni arterovenose cerebrali, 16 da gliomi a bassa malignità, 8 da neurinoma dell'acustico, 8 da meningiomi e 11 da tumori maligni radiosensibili: in questi gruppi di pazienti la tecnica si è dimostrata sicura ed efficace. I risultati vengono paragonati a quelli ottenuti con la Gamma Unit di Leksell e col Ciclotrone di Kjellberg.

A Radiation-Induced Hippocampal Vascular Injury Surrogate Marker Predicts Late Neurocognitive Dysfunction

PURPOSE

We aimed to develop a hippocampal vascular injury surrogate marker for early prediction of late neurocognitive dysfunction in patients receiving brain radiation therapy (RT).

METHODS AND MATERIALS

Twenty-seven patients (17 males and 10 females, 31-80 years of age) were enrolled in an institutional review board-approved prospective longitudinal study. Patients received diagnoses of low-grade glioma or benign tumor and were treated by (3D) conformal or intensity-modulated RT with a median dose of 54 Gy (50.4-59.4 Gy in 1.8-Gy fractions). Six dynamic-contrast enhanced MRI scans were performed from pre-RT to 18-month post-RT, and quantified for vascular parameters related to blood-brain barrier permeability, K(trans), and the fraction of blood plasma volume, Vp. The temporal changes in the means of hippocampal transfer constant K(trans) and Vp after starting RT were modeled by integrating the dose effects with age, sex, hippocampal laterality, and presence of tumor or edema near a hippocampus. Finally, the early vascular dose response in hippocampi was correlated with neurocognitive dysfunction at 6 and 18 months post-RT.

RESULTS

The mean K(trans) Increased significantly from pre-RT to 1-month post-RT (P<.0004), which significantly depended on sex (P<.0007) and age (P<.00004), with the dose response more pronounced in older females. Also, the vascular dose response in the left hippocampus of females correlated significantly with changes in memory function at 6 (r=-0.95, P<.0006) and 18-months (r=-0.88, P<.02) post-RT.

CONCLUSIONS

The early hippocampal vascular dose response could be a predictor of late neurocognitive dysfunction. A personalized hippocampus sparing strategy may be considered in the future.

Postradiation imaging changes in the CNS: how can we differentiate between treatment effect and disease progression?

A familiar challenge for neuroradiologists and neuro-oncologists is differentiating between radiation treatment effect and disease progression in the CNS. Both entities are characterized by an increase in contrast enhancement on MRI and present with similar clinical signs and symptoms that may occur either in close temporal proximity to the treatment or later in the disease course. When radiation-related imaging changes or clinical deterioration are mistaken for disease progression, patients may be subject to unnecessary surgery and/or a change from otherwise effective therapy. Similarly, when disease progression is mistaken for treatment effect, a potentially ineffective therapy may be continued in the face of progressive disease. Here we describe the three types of radiation injury to the brain based on the time to development of signs and symptoms--acute, subacute and late--and then review specific imaging changes after intensity-modulated radiation therapy, stereotactic radiosurgery and brachytherapy. We provide an overview of these phenomena in the treatment of a wide range of malignant and benign CNS illnesses. Finally, we review the published data regarding imaging techniques under investigation to address this well-known problem.

Biological implications of whole-brain radiotherapy versus stereotactic radiosurgery of multiple brain metastases

OBJECT

The efficacy and safety of treatment with whole-brain radiotherapy (WBRT) or with stereotactic radiosurgery (SRS) for multiple brain metastases (> 10) are topics of ongoing debate. This study presents detailed dosimetric and biological information to investigate the possible clinical outcomes of these 2 modalities.

METHODS

Five patients with multiple brain metastases (n = 11-23) underwent SRS. Whole-brain radiotherapy plans were retrospectively designed with the same MR image set and the same structure set for each patient, using the standard opposing lateral beams and fractionation (3 Gy × 10). Physical radiation doses and biologically effective doses (BEDs) in WBRT and SRS were calculated for each lesion target and for the normal brain tissues for comparison of the 2 modalities in the context of clinical efficacy and published toxicities.

RESULTS

The BEDs targeted to the tumor were higher in SRS than in WBRT by factors ranging from 2.4- to 3.0- fold for the mean dose and from 3.2- to 5.3-fold for the maximum dose. In the 5 patients, mean BEDs in SRS (calculated as percentages of BEDs in WBRT) were 1.3%-34.3% for normal brain tissue, 0.7%-31.6% for the brainstem, 0.5%-5.7% for the chiasm, 0.2%-5.7% for optic nerves, and 0.6%-18.1% for the hippocampus.

CONCLUSIONS

The dose-volume metrics presented in this study were essential to understanding the safety and efficacy of WBRT and SRS for multiple brain metastases. Whole-brain radiotherapy results in a higher incidence of radiation-related toxicities than SRS. Even in patients with > 10 brain metastases, the normal CNS tissues receive significantly lower doses in SRS. The mean normal brain dose in SRS correlated with the total volume of the lesions rather than with the number of lesions treated.

Radiation therapy in neurologic disease

Radiotherapy is a primary mode of treatment of many of the disease entities seen by the neurologist. Therefore knowledge of how ionizing radiation works and when it is indicated is a crucial part of the field of Neurology. The neurologist may also be confronted with some of the side effects and complications or radiotherapy treatment. This chapter attempts to serve as a review of the current day process of radiotherapy, a brief review of biology and physics of radiation, and how it is used in the treatment diseases which are common to the Neurologist. In addition we review the more commonly seen side effects and complications of treatment which may be seen by the neurologist.

Whole brain radiotherapy for brain metastasis

Whole brain radiotherapy (WBRT) is a mainstay of treatment in patients with both identifiable brain metastases and prophylaxis for microscopic disease. The use of WBRT has decreased somewhat in recent years due to both advances in radiation technology, allowing for a more localized delivery of radiation, and growing concerns regarding the late toxicity profile associated with WBRT. This has prompted the development of several recent and ongoing prospective studies designed to provide Level I evidence to guide optimal treatment approaches for patients with intracranial metastases. In addition to defining the role of WBRT in patients with brain metastases, identifying methods to improve WBRT is an active area of investigation, and can be classified into two general categories: Those designed to decrease the morbidity of WBRT, primarily by reducing late toxicity, and those designed to improve the efficacy of WBRT. Both of these areas of research show diversity and promise, and it seems feasible that in the near future, the efficacy/toxicity ratio may be improved, allowing for a more diverse clinical application of WBRT.

Radiation Exposure during Endovascular Procedures

Objective:

The duration of fluoroscopy exposure is routinely recorded as part of endovascular procedures. However, to better relate the duration of exposure to actual doses of surface and intracranial radiation, we compared surface doses during endovascular procedures with intracranial doses in a cadaver model exposed to lateral fluoroscopy.

Methods:

Optically stimulated luminescence dosimeter chips (Landauer, Glenwood, IL) were used to measure the cranial surface dose of three consecutive patients undergoing endovascular procedures. Bitemporal craniotomies were performed on a cadaver. Dosimeter chips were placed on both the ipsilateral and contralateral skin and meningeal surfaces, and the cadaver was exposed to lateral fluoroscopy. Finally, to assess mean fluoroscopy times in patients undergoing embolization procedures, the operative notes of 100 consecutive patients were reviewed.

Results:

Three patients undergoing endovascular treatment received peak doses of 0.24, 0.31, and 1.38 Gy, respectively. In the cadaver, the peak surface dose recorded after 120 minutes of exposure was 1.71 Gy. The cranium and scalp absorbed or reflected 29% of the surface dose. Time in minutes of fluoroscopy was found to correlate with surface dose (R2 = 0.925).

Conclusion:

Our data show that radiation exposure during endovascular treatment can reach clinically significant levels. The surface doses recorded during this study were comparable to the mean dose of 1.5 Gy estimated by others to increase the relative risk of inducing meningiomas, gliomas, and nerve sheath tumors. Pending long-term follow-up of patients exposed to endovascular procedures, consent for possible long-term sequelae of radiation may be warranted.

Incidence of brain atrophy and decline in mini-mental state examination score after whole-brain radiotherapy in patients with brain metastases: a prospective study

PURPOSE

To determine the incidence of brain atrophy and dementia after whole-brain radiotherapy (WBRT) in patients with brain metastases not undergoing surgery.

METHODS AND MATERIALS

Eligible patients underwent WBRT to 40 Gy in 20 fractions with or without a 10-Gy boost. Brain magnetic resonance imaging or computed tomography and Mini-Mental State Examination (MMSE) were performed before and soon after radiotherapy, every 3 months for 18 months, and every 6 months thereafter. Brain atrophy was evaluated by change in cerebrospinal fluid-cranial ratio (CCR), and the atrophy index was defined as postradiation CCR divided by preradiation CCR.

RESULTS

Of 101 patients (median age, 62 years) entering the study, 92 completed WBRT, and 45, 25, and 10 patients were assessable at 6, 12, and 18 months, respectively. Mean atrophy index was 1.24 +/- 0.39 (SD) at 6 months and 1.32 +/- 0.40 at 12 months, and 18% and 28% of the patients had an increase in the atrophy index by 30% or greater, respectively. No apparent decrease in mean MMSE score was observed after WBRT. Individually, MMSE scores decreased by four or more points in 11% at 6 months, 12% at 12 months, and 0% at 18 months. However, about half the decrease in MMSE scores was associated with a decrease in performance status caused by systemic disease progression.

CONCLUSIONS

Brain atrophy developed in up to 30% of patients, but it was not necessarily accompanied by MMSE score decrease. Dementia after WBRT unaccompanied by tumor recurrence was infrequent.

Stereotactic radiosurgery associated neurotoxicity

Stereotactic radiosurgery (SRS) is an evolving therapeutic modality for well demarcated intracranial lesions. Since the inception of stereotactic radiosurgery the types of parenchymal CNS lesions addressed by this mode of treatment has increased. All modern stereotactic radiosurgical procedures employ several common features. Patients are fitted with a stereotactic head frame or fiducial markers followed by radiographic imaging which allows for external reference points and three-dimensional mapping of the intracranial lesion. Armed with this information a highly conformal treatment plan is developed to deliver a high dose of radiation to a sharply defined target, with rapid dose fall-off outside the lesion volume. While an extremely effective therapeutic option, SRS is not without risk of neurotoxicity, with radiation necrosis being the most commonly recognized complication. The neurotoxic effects of SRS are reviewed and discussed.

Delayed vascular injury after single high-dose irradiation in the rat brain: histologic immunohistochemical, and angiographic studies

PURPOSE

To investigate structural and functional changes in rats after focal brain irradiation by using histologic, immunohistochemical, and angiographic methods.

MATERIALS AND METHODS

Sixty rats were irradiated stereotactically with photons from a 15-MeV linear accelerator. Two collimators and single doses ranging from 20 to 100 Gy were used to treat stereotactically defined areas of 3.7- and 4.7-mm cross section (80% isodose) in the right frontal lobe. The dose-response relationship for the end-point necrosis at 19 months revealed a mean tolerance dose (D50) of 34.2 Gy (standard errors: +4.1, -3.7 Gy). Histologic, immunohistochemical, and angiographic examinations were performed to evaluate delayed radiation effects.

RESULTS

All animals irradiated with 100 Gy developed radiation necrosis after 9 months. Microangiography and immunohistochemical fluorescence staining of the endothelial cells revealed dose-dependent vascular dilatation and rarefaction. Animals irradiated with 20-50 Gy showed no morphologic changes after 9 months. With irradiation of 30-50 Gy, histologic vascular changes that increased with dose were found after 19 months. At that time, no changes were detected after irradiation with 20 Gy with both field sizes and after irradiation with 30 Gy and the 2-mm collimator. Radiation-induced functional disturbances of the brain vasculature could be demonstrated by extravasation of contrast medium by using a microangiographic technique.

CONCLUSION

The observed effect had a definite dependence on dose, volume, and time after treatment.

Central nervous system metastasis in breast cancer

BACKGROUND AND PURPOSE

Central nervous system (CNS) metastasis occurs in at least 30% of patients with breast cancer. Standard treatment is the same as in other solid tumors, though clinical behavior, and sensitivity to radiation therapy (RT) and to chemotherapy may differ considerably. Most of these patients die within a few months, but a substantial subgroup may survive a year or more. The last decade has given rise to new diagnostic methods, new surgical and radiotherapeutic techniques, and the clinical evidence of a chemotherapy permissive blood-brain barrier in CNS metastases. The literature was reviewed to assess the clinical impact of early diagnosis, recognition of prognostic factors, and of the recently developed therapeutic approaches.

MATERIAL AND METHODS

Review of the literature on CNS involvement in breast cancer focusing on clinical studies on early diagnosis, new modes of treatment, and factors influencing outcome.

RESULTS

Although randomized studies are still awaited, systemic chemotherapy seems a valuable alternative for RT of brain metastases in selected cases. In meningeal carcinomatosis, long survival may be independent of intraventricular chemotherapy. Neurotoxicity of intensive intraventricular treatment is considerable. In epidural metastasis, early diagnosis with prompt start of treatment remains the crucial factor for outcome. Radiation therapy is the mainstay of treatment of epidural metastasis, but new surgical techniques and even systemic chemotherapy should be considered in selected cases.

CONCLUSIONS

Recognition of prognostic factors combined with appropriate use of various recently developed therapeutic possibilities will improve the clinical outcome including better local tumor control and less treatment-induced neurotoxicity in a considerable number of patients with CNS metastasis from breast cancer.

Final results of the Royal College of Radiologists' trial comparing two different radiotherapy schedules in the treatment of cerebral metastases

Between February 1990 and February 1993, 25 centres in the UK recruited 544 patients into a prospective randomized trial comparing two whole-brain radiotherapy regimens (30 Gy in ten fractions over 2 weeks versus 12 Gy in two fractions on consecutive days) for the treatment of patients with symptomatic cerebral metastases. Of these patients 533 were eligible for analysis: 270 assigned to the two-fraction arm and 263 to the ten-fraction arm. The two groups were well balanced with respect to patient characteristics. Median survival was 77 days with two fractions (95% CI 68-89) and 84 days for the longer schedule (95% CI 67-102). Analysis of the survival curves showed a marginal advantage for ten fractions (P = 0.04). Performance status (P = 0.0001), site of primary tumour (P = 0.006), dose of dexamethasone (P = 0.004), age (P = 0.04) and randomization treatment (P = 0.03) were independant factors associated with survival. The classification of patients into good or poor risk groups based on these factors, excluding treatment, showed highly significant differences in survival (P < 0.0001). Predictive models suggested that any benefit attributable to the longer radiotherapy schedule was confined to those in a good prognostic group (these patients formed 22% of the study population). Radiation related side effects, other than alopecia, were seen in 12% of patients receiving two fractions and 8% of those given ten fractions. The short survival of many patients hampered the assessment of response, but overall responses were seen in 39% of those given two fractions and 44% of patients receiving ten fractions. These results suggest that any increase in survival due to longer radiotherapy treatment is confined to good prognosis patients, but, for the majority, there is no advantage and the value of radiotherapy for these patients relates purely to the possibility of control or relief of distressing symptoms.

Brain tumors

This synthesis of the literature on radiotherapy for brain tumors, ie, cancer originating in the central nervous system (CNS), is based on 81 scientific articles, including 25 randomized studies, 13 prospective studies, and 25 retrospective studies. These studies involve 11,081 patients. A more comprehensive chapter on brain tumors may be ordered from SBU. Curative treatment is not available for patients with highly malignant glioma (grades III and IV). Postoperative radiotherapy for highly malignant glioma extends patients' survival, with good quality of life, by several weeks to several months. Virtually all patients die from this disease. Although the clinical benefits from radiotherapy, measured as survival, appear to be modest, it is more effective than any chemotherapy tested thus far. The clinical effects of radiotherapy for highly malignant glioma are improved only marginally by altering factors such as absorbed dose, fractionation, irradiated tissue volume, radiation quality, or by adding radiosensitizing substances. Radiotherapy alone usually provides a clear but temporary improvement in patients with highly malignant glioma, hence it clearly has a palliative benefit. Postoperative radiotherapy for low-grade malignant gliomas (grades I and II) may extend survival. It also reduces tumor volume. No evidence shows that radiotherapy alone or postoperatively can lead to cure. In patients who have undergone subtotal meningioma resection, postoperative radiotherapy substantially reduces the risk for recurrence and extends life, and is thereby indicated. Radiotherapy is not indicated following macroscopic radical meningioma surgery. Patients with brain metastases experience rapid neurological improvement following radiotherapy to the whole brain, and this palliative effect often remains throughout the remainder of the patient's life. Palliative radiotherapy, often to large volumes of the CNS, is therefore motivated in a large proportion of the patient groups. In a smaller group of patients with solitary metastases, radiotherapy may be given postoperatively following radical neurosurgery. Life may be extended in this group, otherwise radiotherapy does not influence survival. Stereotactic radiotherapy of solitary, mainly spherical metastases in the brain is often superior to other known methods with respect to palliation and survival. The number of patients is, however, relatively small.

0-7-21 radiation therapy for the palliation of advanced cancer in dogs

The 0-7-21 radiation therapy protocol was investigated as a palliative treatment in dogs with advanced malignancies. Twenty-four dogs with a variety of tumor types were irradiated using 800 cGy fractions given on days 0, 7, and 21. Twenty-three dogs were evaluated. Palliative response was assessed using a quality of life instrument developed for veterinary use. This pain score was based on owner response to questions regarding analgesic requirement, activity level, appetite, and degree of lameness in the affected dogs. Seventeen (74%) of the 23 dogs experienced complete pain relief, and 3 (13%) obtained partial relief. Of the 17 dogs that achieved a complete response, pain recurred in 8 at a median time of 70 days. Six dogs were alive and free of pain up to 557 days after irradiation. The 0-7-21 protocol was well tolerated; pain relief occurred quickly, and acute radiation reactions were negligible.

The influence of volume on the tolerance of the brain to radiosurgery

Radiosurgery (delivery of a high dose of radiation to a small volume of the brain) is usually well tolerated since the volume of brain irradiated is small. Despite growing interest in radiosurgery, the influence of the volume of brain irradiated on the tolerance of the brain to radiation is not well understood. The results of six studies reporting clinically significant radiation reactions following radiosurgery for arteriovenous malformations are reviewed. In the combined series, 23 (9%) of 255 patients developed a clinically significant radiation reaction. The volume of brain irradiated and the dose delivered in each of these 23 patients are presented. The compiled data suggest that the previously presented guidelines may underestimate the risks of radiosurgery. Additional clinical and experimental data are needed to determine "safe" doses of radiation to be used during radiosurgery.

Reduction in radiation-induced brain injury by use of pentobarbital or lidocaine protection

To determine if barbiturates would protect brain at high doses of radiation, survival rates in rats that received whole-brain x-irradiation during pentobarbital- or lidocaine-induced anesthesia were compared with those of control animals that received no medication and of animals anesthetized with ketamine. The animals were shielded so that respiratory and digestive tissues would not be damaged by the radiation. Survival rates in rats that received whole-brain irradiation as a single 7500-rad dose under pentobarbital- or lidocaine-induced anesthesia was increased from between from 0% and 20% to between 45% and 69% over the 40 days of observation compared with the other two groups (p less than 0.007). Ketamine anesthesia provided no protection. There were no notable differential effects upon non-neural tissues, suggesting that pentobarbital afforded protection through modulation of ambient neural activity during radiation exposure. Neural suppression during high-dose cranial irradiation protects brain from acute and early delayed radiation injury. Further development and application of this knowledge may reduce the incidence of radiation toxicity of the central nervous system (CNS) and may permit the safe use of otherwise "unsafe" doses of radiation in patients with CNS neoplasms.

Stereotactic radiosurgery of the brain using a standard linear accelerator: a study of early and late effects

Between February 1986 and December 1988, 44 patients were treated with stereotactic radiosurgery using a standard linear accelerator. Twenty one patients were treated for cerebrovascular abnormalities and 23 patients were treated for intracranial tumors. Fifteen of the 23 patients treated for intracranial tumors had received previous radiotherapy. The range of doses given by radiosurgery was 1000-2500 cGy. Nausea and vomiting occurred in seven patients within six hours of treatment. The incidence and symptoms were correlated with the dose of radiation to the vomiting center (area postrema) with the median dose to the postrema in symptomatic patients being 618 cGy compared to a range of less than 5 to 184 cGy in the remaining 36 asymptomatic patients. Temporary alopecia occurred in a single patient who received 400 cGy to the scalp. Alopecia did not occur in the remaining 43 patients who received from less than 5 to 175 cGy. Two patients treated for arteriovenous malformations developed an enhancing lesion on CT scanning (one with cerebral edema) on follow-up CT scanning six and twenty-eight months following radiosurgery. The location of these enhancing lesions corresponded to the volumes treated. In one patient, the enhancing pattern and edema disappeared within 18 months of treatment and no neurological deficits developed. Aphasia occurred in one patient treated for a recurrent glioma two hours following treatment to the left temporal lobe and cleared within 12 h of radiosurgery. One patient with an arteriovenous malformation of the pons developed weakness of the contralateral arm and leg six weeks following treatment and this has slowly resolved over the last 12 months. In conclusion, the complications to date have been self-limited and appear to be directly related to the dose and area of brain treated. Prior radiation therapy has not been associated with increased risk of complication in patients treated with radiosurgery for recurrent tumors to date.

The acute onset of nausea and vomiting following stereotactic radiosurgery: correlation with total dose to area postrema

From 1986 to 1988, 44 patients have been treated for tumors or vascular lesions with stereotactic radiosurgery using a modified standard linear accelerator. In seven patients, nausea and vomiting occurred within 6 hours after the completion of radiosurgery. One of these patients with nausea and occasional vomiting pretreatment had exacerbation several hours after treatment, in spite of droperidol and prochlorperazine prophylaxis. Nausea and vomiting in the other six patients was self-limited and was completely resolved by 12 hours from onset. None of these six patients suffered from nausea and vomiting before treatment. This was directly correlated with the total dose to the vomiting center in the floor of the fourth ventricle (area postrema). The median dose to the vomiting center in the seven patients was 618 cGy (range 275-1257). The final patient in the series received 1088 cGy to the area postrema after droperidol and dexamethasone prophylaxis without developing nausea or vomiting. In the remaining 36 patients who received from less than 5 to 184 cGy to area postrema, nausea and vomiting did not occur. We recommend that patients treated with large fractions of radiation by radiosurgery in this area be premedicated appropriately.

Radiotherapy of brain metastases from carcinoma of the bronchus

A retrospective study of 68 patients suffering from carcinoma of the bronchus with brain metastases is presented. They were treated in the Radiotherapy Department, Queen Elizabeth Hospital over a 5-year period (1982 to 1986). There were 42 male and 26 female patients. The age range was 30 to 78 years (median 58.5). All patients were treated with whole-brain photon irradiation using lateral opposing fields. The dosage could be divided into two groups: 30 Gy given in 10 to 15 daily fractions (30 patients), or 22.5 Gy given in five daily fractions (38 patients). There was no significant difference in the actuarial survival of the two groups (P = 0.37), the median survival being 7 and 6 weeks respectively. There was no difference in survival between the groups with different histological subtypes (P = 0.43). The 5-day short fractionation is the preferred treatment as it gives patients more time away from hospital. In 80.4% of patients there was progression of neurological symptoms before death. Increasing the dose of radiotherapy to the main bulk of tumour may improve the symptom-free survival or overall survival.

Single brain metastasis of non-small cell lung carcinoma. Study of survival among 54 patients

We studied 54 patients treated for non-small cell lung carcinoma with single brain metastasis presenting between 1980 and 1985. Better survival was obtained in cases of patients presenting a fair neurological condition who were treated by surgery. Histological condition and date of onet of metastasis had no significant influence on survival. Combined treatment of both primary lung tumour and brain metastasis was a favourable prognosis element, and surgical resection of both locations led to the best results in terms of duration and quality of survival.

Radiation therapy for neoplasms of the brain

The effectiveness and complications of radiation therapy for brain neoplasms are reviewed. While the available data suggest a favorable influence and outcome, randomized studies are needed to further optimize radiation therapy techniques and to integrate new therapeutic modalities.

Different fractionation schedules in radiation treatment of cerebral metastases

Multiple daily fractionation (MDF) was compared, in a cooperative study, with conventional fractionation (CF) in the radiation treatment of brain metastases. The 103 patients treated by MDF and the 44 given CF showed a similar response, in terms of neurologic improvement, survival, quality of residual life, and treatment-related morbidity. The hypothesis that MDF might give a better therapeutic ratio than CF was not confirmed in the present series. The short time period required gives MDF advantages in clinical practice.

The role of radiation therapy in the palliation of metastatic genitourinary tract carcinomas. A study of the Radiation Therapy Oncology Group

The Radiation Therapy Oncology Group has conducted several randomized clinical trials to evaluate the efficacy of various radiation therapy schedules in palliating symptomatic brain and bone metastases. Among the patients entered in these studies, there were 225 patients with primary tumors of the genitourinary tract. Of these, 68 patients had cerebral metastases and 157 patients had osseous metastases. These patients were analyzed further as to the effectiveness of radiotherapy in palliation of their symptoms, and the results were compared to those for comparable metastases in patients with other primary sites. Relief of symptoms occurred in 54% of neurologic function (NF) Class III and 28% of NF Class II patients with cerebral metastases. This result compared favorably with those for the total group of patients consisting of patients with brain and bone metastases from various primary sites. Improvement was seen in 80% of patients with headaches and 88% of patients with convulsions. Motor loss improved in 62% of the patients. Of the patients with bone metastases, 81% with prostatic carcinoma and 59% with renal primaries had lessening of pain. Complete relief of pain at eight weeks occurred in 36% of the patients, compared to 24% in the total group. The median survival for patients with solitary bone metastases from a prostatic primary was 39 weeks, compared to 30 weeks for those with multiple metastatic sites.

Radiation therapy for brain metastases

We treated 183 patients who had brain metastases with whole-brain radiation therapy (RT) and adrenocorticosteroids utilizing a new high-dose radiation protocol. Treatment produced neurological improvement in 135 patients (74%); there was no change in 37 (20%), and deterioration occurred in 11 (6%). Of those patients who improved, two-thirds maintained neurological improvement for the remainder of their lives or for at least nine months, and one-third relapsed. One-third of those who relapsed improved again with steroids or further RT. Clinical improvement paralleled tumor regression on CT scan. Despite the clinical response, median survival was only twelve weeks; 24% lived six months and 8% lived one year. Death resulted from progressive brain disease in 16% of the patients. Two-thirds of the patients died of advancing systemic disease in the setting of stable, improved neurological function. These data suggest that the majority of patients with brain metastases benefit from RT and that systemic cancer, not central nervous system disease, limits the length of life.

Palliative irradiation of brain metastases

The records of 121 patients with brain metastases from a 3-year-period were reviewed. Radiation therapy was given to 113 patients, 80 per cent received 30 Gy in 2 weeks. Before irradiation 11 were operated upon. Significant neurologic improvement was obtained in 60 per cent of the irradiated cases. Recurrences, retreatment and the necessity of higher initial doses in selected cases are discussed.