Effect of Cobalt-60 Calibration Dose-Rate on Arteriovenous Malformation Obliteration after Stereotactic Radiosurgery

PURPOSE/OBJECTIVE(S)

Stereotactic radiosurgery (SRS) dose rate - how old the cobalt-60 sources are - is known to influence outcomes for some neurologic conditions and benign tumors, but it is not known if SRS dose rate influences arteriovenous malformation (AVM) obliteration. The objective of this study is to determine the association between cobalt-60 calibration dose rate and cerebral AVM obliteration in patients treated with SRS. Our hypothesis is that higher SRS dose rates are associated with increased incidence of cerebral AVM obliteration.

MATERIALS/METHODS

We performed a retrospective study of 361 patients undergoing 411 AVM-directed SRS treatments between 2005 and 2019 at a single institution. Obliteration was confirmed with digital subtraction angiogram or MRI (if patient refused angiography). Lesion characteristics, SRS treatment details, and post-treatment obliteration and toxicities were recorded. Univariate and multivariate proportional hazards regression models of AVM outcomes with regard to SRS dose rate were performed, controlling for factors such as Spetzler-Martin Grade, maximum AVM extent, prior hemorrhage and prior embolization.

RESULTS

At 10 years post-SRS, 68% of AVMs were obliterated on follow-up imaging. Dose rates >2.9 Gy/min were found to be significantly associated with AVM obliteration compared to those <2.1 Gy/min (p = 0.034, Gray's test). AVM size or Spetzler-Martin grade were also associated with obliteration, with obliteration more likely for smaller lesions, particularly those <3 cm in maximal diameter, or with lower Spetzler-Martin grade. Higher dose rates were not associated with development of post-SRS radiologic or symptomatic edema, though larger AVM volume was associated with both types of edema.

CONCLUSION

Patients with cerebral AVMs treated with higher SRS dose rates (from fresh cobalt-60 sources) experience higher incidences of obliteration, without a significant change in the risk of post-treatment edema. These findings suggest that clinics offering SRS for AVMs should regularly renew cobalt-60 radiation sources to maintain high therapeutic dose rates.

A Prospective Study of Machine Learning-Assisted Radiotherapy Planning for Patients Receiving 54 Gy to the Brain

PURPOSE/OBJECTIVE(S)

Radiotherapy (RT) planning is presently a semi-manual, iterative, labor-intensive process which may result in unnecessary variation in plan quality. To improve treatment plan quality and decrease RT planning time, we conducted a prospective, blinded study to compare machine learning-assisted planning with conventional manual planning for patients receiving 54 Gy in 30 fractions for a primary brain tumor.

MATERIALS/METHODS

From January 31, 2022 to January 10, 2023, 40 patients receiving 54 Gy for primary CNS tumors were prospectively enrolled (median age 50 years, range 4-78 years). Patients underwent standard CT/MR simulation and target/OAR delineation by the treating radiation oncologist. Each patient had one ML plan and 1-2 manual RT plans created by different planners. The reviewing oncologist was blinded to planning method by removing optimization and IMRT/VMAT beam arrangement details from all plans, which were then rated based on clinical acceptability, target coverage, OAR sparing, conformity, and dose-fall off. One preferred plan was chosen and used for clinical treatment.

RESULTS

A total of 115 plans for 40 patients were evaluated: 40 ML plans (35% of all plans), and 75 manual plans (65% of all plans; 5 and 35 patients had 1 and 2 manual plans created, respectively). ML plans required a mean planning time of 65 min as compared to 107 min for manual plans, with a mean time savings of 41 min per patient (paired t-test p = 0.002). 97% of ML plans (95% confidence interval [CI] 85-100) and 96% of manual plans (95% CI 87-99) were designated clinically acceptable by the treating radiation oncologist. While ML-assisted plans represented 35% of plans evaluated, they were chosen as preferred for clinical treatment in 43% of cases (17/40, 95% CI 29-58, p = 0.32). Median doses to the brain (10.8 Gy vs. 11.3 Gy, Wilcoxon rank-sum p = 0.012) and brain minus PTV (9.2 Gy vs 10.0 Gy, Wilcoxon rank-sum p = 0.009) were lower with ML planning versus manual planning, respectively. Doses to other structures, including hippocampi, cochlea, pituitary and hypothalamus were not statistically different.

CONCLUSION

In this prospective study with blinded oncologist evaluation, ML-assisted RT planning for primary CNS tumors was faster than manual planning, and produced a very high rate of acceptable plans with similar or superior OAR sparing. Future work will be undertaken to iteratively refine the ML model using the preferred cases from this study.

Dose Reductions to Critical Brain Organs-at-Risk and Better Cognition in Children with Medulloblastoma Receiving Proton Therapy

PURPOSE/OBJECTIVE(S)

Our group previously demonstrated an improvement in cognition among children with medulloblastoma treated with proton therapy, as compared to photon therapy. However, the reason for this cognitive improvement was unclear. In this study, our aim was to determine whether dose to critical brain structures acted as a mediator of improved cognition in patients treated with proton therapy.

MATERIALS/METHODS

In this retrospective study, a cohort of 75 children with medulloblastoma from two institutions was assembled (39 photon, 36 proton). Included patients were treated with similar radiation and cognitive follow-up protocols. Study endpoints were verbal comprehension (VCI), perceptual reasoning (PRI), working memory (WMI), processing speed (PSI) indices and full-scale IQ (FSIQ). Brain structures were segmented and dose comparisons by RT modality were compared using independent t-tests. Linear mixed effects models with random intercepts were created to evaluate cognitive endpoints using R version 4.2.2.

RESULTS

Median follow-up from RT to last cognitive assessment was 4.8 years. Total dose, including RT boost, was slightly lower in the proton cohort than the photon cohort (mean, 54.6 Gy vs. 56.1 Gy, respectively, p < 0.001). Eleven children (31%) treated with proton therapy received 36 Gy CSI, while 6 children (15%) treated with photon therapy received 36 Gy CSI (p = 0.07). Children treated with proton therapy had reduced total doses to the brain (mean, D40), left and right temporal lobes (mean, D40, D50), and left and right hippocampi (mean, D40, D50 - see Table). After adjustment for age at RT and posterior fossa syndrome, higher whole brain mean dose and time since RT were associated with greater decrease in VCI (p = 0.033), higher left temporal D50 and time since RT with greater decrease in PRI (p = 0.031), higher whole brain D40 and time since RT with greater decrease in PSI (p < 0.001) and FSIQ (p = 0.030).

CONCLUSION

Our study demonstrates that proton therapy for patients with medulloblastoma reduces dose to normal brain tissues, which is associated with better intellectual outcomes. Children with medulloblastoma who undergo RT should be treated with proton therapy, if available.

Correlation between Cranial Nerve Microstructural Characteristics and Vestibular Schwannoma Tumor Volume

BACKGROUND AND PURPOSE

Vestibular schwannomas are common cerebellopontine angle tumors arising from the vestibulocochlear nerve and can result in cranial nerve dysfunction. Conventional MR imaging does not provide information that could correlate with cranial nerve compression symptoms of hearing loss or imbalance. We used multitensor tractography to evaluate the relationship between the WM microstructural properties of cranial nerves and tumor volume in a cohort of patients with vestibular schwannomas.

MATERIALS AND METHODS

A retrospective study was performed in 258 patients with vestibular schwannomas treated at the Gamma Knife clinic at Toronto Western Hospital between 2014 and 2018. 3T MR images were analyzed in 160 surgically naïve patients with unilateral vestibular schwannomas. Multitensor tractography was used to extract DTI-derived metrics (fractional anisotropy and radial, axial, and mean diffusivities of the bilateral facial and vestibulocochlear nerves [cranial nerves VII/VIII]). ROIs were placed in the transition between cisternal and intracanalicular segments, and images were analyzed using the eXtended Streamline Tractography reconstruction method. Diffusion metrics were correlated with 3D tumor volume derived from the Gamma Knife clinic.

RESULTS

DTI analyses revealed significantly higher fractional anisotropy values and a reduction in axial diffusivity, radial diffusivity, and mean diffusivity (all P < .001) within the affected cranial nerves VII and VIII compared with unaffected side. All specific diffusivities (axial, radial, and mean diffusivity) demonstrated an inverse correlation with tumor volume (axial, radial, and mean diffusivity, P < .01).

CONCLUSIONS

Multitensor tractography allows the quantification of cranial nerve VII and VIII WM microstructural alterations in patients with vestibular schwannomas. Our findings support the hypothesis that tumor volume may cause microstructural alterations of the affected cranial nerves VII and VIII. This type of advanced imaging may represent a possible avenue to correlate diffusivities with cranial nerve function.

PRODIGE: a randomized placebo-controlled trial of dalteparin low-molecular-weight heparin thromboprophylaxis in patients with newly diagnosed malignant glioma

BACKGROUND AND OBJECTIVES

Venous thromboembolism (VTE) occurs in 20-30% of patients with malignant glioma per year of survival. We tested the efficacy of long-term dalteparin low-molecular-weight heparin (LMWH) for prevention of VTE in these patients.

PATIENTS/METHODS

Adults with newly diagnosed malignant glioma were randomized to receive dalteparin 5000 anti-Xa units or placebo, both subcutaneously once daily for 6 months starting within 4 weeks of surgery. Treatment continued for up to 12 months. The primary outcome was the cumulative risk of VTE over 6 months. The target sample size was 512 patients. Events were adjudicated by a committee unaware of treatment.

RESULTS

The trial began in 2002 and closed in May 2006 because of expiration of study medication. Ninety-nine patients were randomized to LMWH and 87 to placebo. Twenty-two patients developed VTE in the first 6 months: nine in the LMWH group and 13 in the placebo group [hazard ratio (HR) = 0.51, 95% confidence interval (CI): 0.19-1.4, P = 0.29]. At 6 months, there were three major bleeds on LMWH and none on placebo; at 12 months, 5 (5.1%) major bleeds on LMWH and 1 (1.2%) on placebo occurred (HR = 4.2, 95% CI: 0.48-36, P = 0.22). All major bleeds were intracranial and occurred while on study medication. The 12-month mortality rates were 47.8% for LMWH and 45.4% for placebo (HR = 1.2, 95% CI: 0.73-2.0, P = 0.48).

CONCLUSIONS

Trends suggesting reduced VTE and increased intracranial bleeding were seen in the LMWH thromboprophylaxis group. The role of long-term anticoagulant thromboprophylaxis in patients with brain tumors remains uncertain.

A population-based study of malignant spinal cord compression in Ontario

DESIGN

Population-based cohort study.

BACKGROUND

Malignant spinal cord compression (MSCC) has long been recognized as an important complication of cancer, but its incidence is unknown.

OBJECTIVES

To describe the incidence, the management, and the outcome of MSCC in the cancer population of the Canadian province of Ontario.

METHODS

Episodes of MSCC, and treatments used for each episode, were identified by linking electronic hospital separation records and cancer centre records to Ontario's population-based cancer registry. The cumulative frequency of MSCC in the last 5 years of life was described in the 121435 patients who died of cancer in Ontario between 1990 and 1995. Survival after the first episode of MSCC, and duration of hospitalization with MSCC, was described.

RESULTS

The cumulative probability of experiencing at least one episode of MSCC in the 5 years preceding death from cancer was 2.5% overall, and ranged from 0.2% in cancer of the pancreas to 7.9% in myeloma. Overall, 60.2% of first episodes of MSCC were treated with primary radiotherapy, and 16.1% with surgery +/- postoperative radiotherapy, while in the remaining 23.7%, there was no record of radiotherapy or surgery. Overall, the median survival following the first episode of MSCC was 2.9 months. The diagnosis of MSCC was associated with a doubling of the time spent in hospital in the last year of life.

CONCLUSION

MSCC is a fairly common occurrence among patients dying of cancer. There is a 40-fold variation in the cumulative incidence of MSCC among different types of cancer.

A retrospective analysis of 52 cases of spinal cord glioma managed with radiation therapy

PURPOSE

To describe the outcome of primary spinal cord glioma treated with radiation therapy after surgery and to identify variables predictive of outcome.

METHODS AND MATERIALS

A chart review of 52 patients with a diagnosis of spinal cord non-ependymoma glioma at the Princess Margaret Hospital was conducted. Thirty-two patients (62%) were male and 20 (38%) were female. Median age was 32 years (2-76 years). Median follow-up was 3.7 years (2 months to 27 years). Initial surgical management consisted of biopsy alone in 27 (52%) cases, subtotal resection in 20 (38%) cases, and gross total resection in 5 (10%) cases. All patients received postoperative radiation therapy; median total dose was 50 Gy, given in 25 daily fractions (20-60 Gy). Actuarial survival rates were calculated and the influence of patient-, tumor-, and treatment-related variables on outcome was determined.

RESULTS

Five-year overall, cause-specific, and progression-free survivals were 54%, 62%, and 58%, respectively. Ten-year survivals were 45%, 50%, and 43%, respectively. A total of 29 (56%) patients died during the period of review. For 23 (79%) of these patients, death was cancer specific. Progression of tumor was documented in 28 of 52 (54%) patients. The following factors predicted for improved outcome on univariate analysis: age < 18 years, low-grade histology, and length of symptoms prior to diagnosis > 6 months.

CONCLUSION

The outcome of patients in this series is consistent with that of other similar published reports. Specific recommendations are made for the management of this tumor.

Randomized study of brachytherapy in the initial management of patients with malignant astrocytoma

PURPOSE

A randomized study was undertaken to assess the role of brachytherapy as a boost to external beam radiation therapy in the initial management of patients with malignant astrocytomas.

METHODS AND MATERIALS

Inclusion criteria included the following: biopsy-proven supratentorial malignant astrocytoma of brain < or =6 cm in size, not crossing midline or involving corpus callosum, age 18-70, Karnofsky Performance Status (KPS) > or =70. Patients were randomized to external radiation therapy only delivering 50 Gray (Gy) in 25 fractions over 5 weeks or external radiation therapy plus a temporary stereotactic iodine-125 implants delivering a minimum peripheral tumor dose of 60 Gy. Patients were stratified to age < or =50 or >50, and KPS > or =90 or < or =80.

RESULTS

There were 140 patients randomized between 1986 and 1996, 71 to the implant arm and 69 to external irradiation only. Pathologically 125 patients had necrosis noted in their tumor specimen. Factors associated with improved survival in univariate analysis were age < or =50, KPS > or =90, chemotherapy at recurrence, and reoperation at the original tumor site. The Cox proportional hazards model revealed the following significant factors: treatment at recurrence (chemotherapy or reoperation) with a relative risk (RR) of 0.6 (p = 0.004) and KPS > or =90 with a RR 0.6 (p = 0.007). Randomization to the implant arm was associated with a RR of 0.7 (p = 0.07). Median survival for patients randomized to brachytherapy or not were 13.8 vs. 13.2 months, respectively, p = 0.49.

CONCLUSIONS

We conclude that stereotactic radiation implants have not demonstrated a statistically significant improvement in survival in the initial management of patients with malignant astrocytoma.

Accelerated radiation therapy for primary lymphoma of the brain

BACKGROUND AND PURPOSE

We report the results of a pilot study of the use of accelerated radiation therapy for 10 patients with primary lymphoma of the brain.

MATERIALS AND METHODS

There were five females and five males with a median age of 60 years (range 31-77 years) and a median Karnofsky performance status of 60 (range 30-90). Nine patients underwent biopsies only and one patient underwent a partial resection. The radiation therapy consisted of 50 Gy in 25 fractions over 13 consecutive days to the whole brain including all meningeal surfaces. Two fractions were delivered daily with a minimum interval of 6 h between fractions. Treatment was delivered daily right through the weekend with no treatment interruptions.

RESULTS

To date nine patients have died. The median survival was 17 months. Seven patients have demonstrated definite evidence of recurrence (six in the brain and one with positive CSF cytology only). There have been two autopsies, one of which demonstrated diffusely recurrent tumor and the other showing residual disease and radiation demyelination and small areas of necrosis in the pons which undoubtedly was the cause of death at 5 months. One patient alive and free of recurrence at 69 months has bilateral radiation retinopathy and an undiagnosed degenerative neurologic condition.

CONCLUSION

We conclude that this accelerated schedule of radiation therapy is ineffective in improving survival in primary lymphoma of the brain and is associated with unacceptable increased toxicity.

Emergency treatment of malignant extradural spinal cord compression: an evidence-based guideline

PURPOSE

To review the literature for malignant extradural spinal cord compression (MSCC), produce evidence-based recommendations based on the criteria used by the Canadian Task Force on the Periodic Health Examination, and make suggestions regarding future research directives.

METHODS

A systematic review of the literature with explicit study selection and evaluation criteria was performed. Primary outcome measure was posttreatment ambulation rate.

RESULTS

There is good evidence to support the use of high-dose dexamethasone (96 mg/d), but inconclusive evidence for the use of moderate-dose steroids (16 mg/d) in conjunction with radiotherapy (RT) for the treatment of MSCC. Fair evidence exists for not using steroids in patients who are nonparetic and ambulatory pretreatment, and to give radiation to patients with subclinical spinal cord compression (SCC). The remainder of the recommendations are based on inconclusive evidence: RT alone should be the first-line treatment for ambulatory patients except when there is spinal instability, bony compression, or paraplegia on presentation, in which case surgery should be performed. Either modality can be used for paraparetic patients who are nonambulatory. Postoperative RT should be considered for tumor in residua. Ambulatory, undiagnosed patients should have needle biopsy attempted first. Patients should be aggressively screened and educated about SCC.

CONCLUSION

In general, there were very few papers of high methodologic quality found in the literature. More studies are needed to satisfy the validity of many of the clinical decisions that are made today with regard to the management of MSCC.

Post-operative radiotherapy for recurrent dermoid cysts of the spine: a report of 3 cases

We report three cases of recurrent, intraspinal dermoid cysts managed with post-operative radical radiotherapy. In all cases, the period between last surgery and cystic re-accumulation has been lengthened by the use of involved-field radiotherapy. This combined-modality approach could be beneficial in decreasing the probability of recurrence associated with incompletely-resected tumours, or in patients whose co-morbidities put them at increased operative risk for serial neurosurgical procedures.

Primary lymphoma of brain: results of management of a modern cohort with radiation therapy

PURPOSE

To assess the outcome and prognostic factors for patients with primary lymphoma of brain managed with radiation therapy between 1979 and 1988.

METHODS AND MATERIALS

A retrospective review was undertaken of 49 patients referred to Princess Margaret Hospital. There were 25 males and 24 females. Median age was 60 years, with a range of 17-80 years. Tumors were located supratentorially in 35, infratentorially in 10, and both in 4 patients. Single masses were demonstrated on CT brain in 36, and multiple lesions in 13 patients. Cranial irradiation was given in 48, and 11 patients received chemotherapy. All patients in this series were immunocompetent.

RESULTS

Over a follow-up range of 3-11 years of surviving patients, with a median of 6 years, 40/49 patients have died. Overall median survival was 1.4 years (17 months) and 5-year actuarial survival was 26%. Statistical analysis revealed the following significant factors: Karnofsky performance status (KPS), age, and distribution pattern of disease on presenting CT brain. Five-year actuarial survival for patients with a KPS > 60 or <60 was 56% and 10%, respectively (P = 0.01); for patients with age < 60 or >60, 5-year actuarial survival was 42% and 9%, respectively (P = 0.03); for patients with solitary or multiple lesions, 5-year actuarial survival was 30% and 15%, respectively (P = 0.04).

CONCLUSIONS

We conclude that Karnofsky performance status, age, and distribution pattern on pretreatment CT of brain are significant prognostic factors in primary lymphoma of brain, and that new approaches need to be developed for these patients.

Radiotherapy for atypical or malignant intracranial meningioma

PURPOSE

To study the natural history of intracranial atypical and malignant meningiomas, and the role of radiotherapy in the treatment of these tumors.

METHODS AND MATERIALS

The records of the 59 patients who were treated at the Princess Margaret Hospital between 1966 and 1990 with histologically confirmed intracranial atypical or malignant meningiomas were retrospectively reviewed. The median age was 58 years. Twenty-four patients were referred for radiation immediately after diagnosis and the remainder after at least one recurrence. The extent of the most recent surgery prior to radiation was gross total excision in 17, subtotal excision in 35, biopsy in 3, and none or unknown in 4. Seventeen had atypical meningiomas, defined as the presence of mitoses, nuclear atypia, or necrosis. Forty-two had malignant meningiomas on the basis of brain invasion (60%) or a pathologist's designation of malignant or hemangiopericytic meningioma. All patients received megavoltage radiation to a median dose of 50 Gy.

RESULTS

Disease progressed in 39 patients (66%) after radiation. Of these, 36 died of meningioma and 3 were alive after further surgery. The 5-year actuarial overall and cause-specific survivals were 28 and 34%, respectively. Age less than 58, treatment after 1975, and a radiation dose of 50 Gy or more were independently associated with higher cause-specific survival by multivariate analysis.

CONCLUSIONS

Young age, modern imaging and treatment planning techniques, and a postoperative radiation dose of at least 50 Gy contribute to improved outcome in patients with atypical or malignant meningiomas. We recommend that all patients receive radiotherapy immediately after initial surgery.

Medulloblastoma in adults

PURPOSE

To assess the outcome and prognostic factors for adult patients with medulloblastoma managed by postoperative radiotherapy between 1958 and 1988 at the Princess Margaret Hospital.

METHODS AND MATERIALS

A retrospective review was undertaken of 48 patients age 16 years or older who received radiotherapy for medulloblastoma. The median age at diagnosis was 25 years, with 36 male and 12 female patients. Sixteen tumors were confined to midline structures, and 32 were localized to a cerebellar hemisphere or involved midline and lateral structures. The desmoplastic variant was reported in 12 cases. Complete macroscopic removal was achieved in 22 patients, subtotal removal in 23, and biopsy only in 3. Forty-six patients received craniospinal radiation and 2 patients received local irradiation only.

RESULTS

Median overall survival was 7.9 years, and 5- and 10-year overall survival was 62% and 41%, respectively. Significant factors for disease-free survival were M stage (M0 vs. M1-4, p = 0.0005), functional state at the time of radiotherapy (1-2 vs. 3-5, p = 0.005), and the absence or presence of hydrocephalus preoperatively (p = 0.02). Twenty-four patients developed recurrent disease, with 14 relapsing first in the posterior fossa. Subtotal removal of tumor (p = 0.04) was the only factor predictive of posterior fossa relapse.

CONCLUSIONS

Patients with disease outside the posterior fossa at diagnosis, symptomatic patients (neurologic functional state 3-5) at the time of radiotherapy, and those who present with hydrocephalus have poorer disease-free survival. Gross total resection improved posterior fossa control.

Radiation myelopathy following single courses of radiotherapy and retreatment

PURPOSE

To assess the latent time, survival and dose-fractionation factors associated with permanent radiation myelopathy following single and multiple courses of radiotherapy to the spinal cord.

METHODS AND MATERIALS

A retrospective analysis was undertaken of all patients who were registered at the Princess Margaret Hospital between 1955 and 1985, and who developed permanent radiation myelopathy. There were 22 males and 13 females with ages ranging from 30 to 72 years. Twenty-four patients developed permanent myelopathy after one course of radiation therapy and 11 patients following retreatment. Seven patients had histological confirmation of radiation myelopathy at autopsy.

RESULTS

The actuarial survival was 14% at 5 years (median: 8.3 months) from the date of diagnosis of radiation myelopathy. Latent times for myelopathy following a single course of treatment (mean: 18.5 months, 7-57 months), were significantly longer than those after reirradiation (mean: 11.4 months, 4-25 months), p = 0.03. There was not a single incident of myelopathy in patients who received fractionated radiotherapy given once daily to an extrapolated response dose (ERD) of < or = 100 Gy2 (equivalent to 50 Gy in 25 daily fractions). Four patients who developed myelopathy after an ERD of < 100 Gy2 were all treated on accelerated fractionation protocols with multiple fractions given per day. Patients who were reirradiated received significantly higher doses (mean ERD of 148 Gy2) than those who had a single course of treatment (mean ERD of 121 Gy2), p = 0.001.

CONCLUSION

We conclude that the risk of radiation myelopathy following conventionally fractionated radiotherapy to the spinal cord is extremely small; giving multiple fractions per day reduces the spinal cord tolerance; latent time to myelopathy decreases following retreatment; and there is possible long-term recovery of radiation damage in the human spinal cord.

Radiotherapy for brain tumors

Improved techniques of radiotherapy have led to marked improvement in the results of radiotherapy for certain brain tumors, such as medulloblastoma and pineal germinoma, but results for malignant astrocytoma, the most common brain tumor, have been modest. This article reviews results of radiotherapy for brain tumors in adult patients over the last decade and comments on the new approaches being studied.

Glioma arising after radiation therapy for pituitary adenoma. A report of four patients and estimation of risk

BACKGROUND

Many case reports in the literature associate cranial radiation therapy with the development of brain tumors. Quantitation of the risk of second brain tumors after irradiation in childhood is available, but it is seldom reported for those treated by radiation therapy as adults.

METHODS

A retrospective review was made of 367 patient records registered at the Princess Margaret Hospital with a diagnosis of pituitary adenoma from 1972 to 1986. Three hundred five patients treated with megavoltage radiation therapy form the basis of this report. Second brain tumors were identified and the patient case histories described. The risk of second brain tumor after irradiation was estimated by calculating the observed/expected (O/E) ratio, age- and sex-adjusted to the Ontario population.

RESULTS

Of the 305 patients in this study, 4 had glioma of the brain. All gliomas arose within the previous radiation field(s), with a latency of 8-15 years after radiation therapy. Additional treatment was compromised by the location of the glioma and the moderately high doses of radiation received previously; all four patients died of their gliomas. Our cohort of patients had a relative risk of malignant brain tumor 16 times greater than that of the general population in Ontario (P < 0.001; 95% confidence interval, 4.4-41). The cumulative actuarial risk of secondary glioma after radiation therapy was 1.7% at 10 years and 2.7% at 15 years.

CONCLUSIONS

There was a clinically significant increased risk of malignant brain tumor developing after radiation therapy for pituitary adenoma. Because there is no reported association between pituitary adenomas and gliomas of brain, this excess risk is attributed to irradiation. Before advising radiation therapy for pituitary adenoma, the risk:benefit ratio, including the risk of secondary brain tumors, should be carefully considered.

Spinal cord ependymomas: a retrospective analysis of 59 cases

PURPOSE

To determine the outcome of patients with primary spinal ependymoma treated with postoperative radiotherapy and to identify clinical and treatment variables predictive of outcome.

METHODS AND MATERIALS

A retrospective chart review was undertaken of 59 spinal ependymoma patients referred to the Princess Margaret Hospital between 1958 and 1987. All patients were treated with radiation therapy to either the site of the primary tumor or the craniospinal axis. There were 23 female and 36 male patients with a median age of 37 years (range: 8-66 years). Median follow-up was 130 months (range: 1-371 months). Clinical variables including age, sex, length of symptoms, functional status, tumor location, and grade as well as treatment variables including extent of surgery, radiation dose and treatment volume were analyzed for influence on outcome.

RESULTS

Treatment was well-tolerated with no cases of radiation myelopathy identified. Overall actuarial survival at 5 and 10 years was 83% and 75%, respectively. Eleven patients had recurrent tumor with the 9/11 having a component of their recurrence within the treatment field. Median time to recurrence was 2 years with 9 of the 11 recurrences within the first 3 years. Tumor grade was the only independent variable identified as predictive of outcome. Patients with well differentiated tumors had a 5-year cause-specific survival of 97% compared to 71% for those with intermediate or poorly differentiated tumors (p = 0.005).

CONCLUSION

We conclude that postoperative irradiation for patients with spinal ependymomas is associated with a favorable outcome and that tumor grade is a major prognostic factor. Based on results of this series and a review of the literature, specific management recommendations are made for this rare tumor.

Critical appraisal of experimental radiation modalities for malignant astrocytomas

The management of patients with supratentorial malignant astrocytomas has remained a major problem. Patients continue to die from a lack of local control in 90% of cases despite an improvement of median survival seen with the use of postoperative radiation therapy. Because of this, there has been considerable interest in exploring novel ways of possibly improving results. This paper reviews the rationale and clinical results with the use of altered fractionation schemes, brachytherapy, radiation sensitizers, hyperthermia, particle therapy, and radiosurgery in the treatment of these patients. Currently, there is no demonstrated advantage with the use of these experimental modalities in the initial management of patients. There would appear to be some benefit for selected patients who are treated with brachytherapy at recurrence, but its efficacy as part of initial management remains to be determined determined in ongoing randomized prospective trials.

A critical appraisal of the role of brachytherapy for pediatric brain tumors

While brachytherapy is increasingly being utilized in adult patients with brain tumors, there has been very little experience with this approach in pediatric patients. This report reviews the current published experience with brachytherapy for brain tumors in children. Intracavitary irradiation with radioactive colloid is quite effective in controlling cystic craniopharyngiomas and represents an alternative approach to this subgroup of patients with craniopharyngiomas. There has been a substantial experience with the use of permanent interstitial implants in cases of low-grade astrocytoma in Europe, but its value is difficult to judge because of the variable natural history of these slow-growing neoplasms. Very few high-grade astrocytomas have been treated with brachytherapy in children, but children with localized recurrences after conventional therapy should be considered for this approach.

Malignant tumors of the head and neck in a young population

Malignant tumors in the head and neck region are rare in patients under the age of 30 years. The survival rate in our group compared favorably with the rate for adults with similar tumors and supports the administration of aggressive treatment. Radiation therapy in the formative years can arrest skeletal growth and cause tissue atrophy which produces facial asymmetry, but it does give in balance a better functional result and less mutilation than does radical surgery. The risk of development of a second malignant tumor with the administration of modern treatment appears to be minimal. There is an urgent need for better documentation of etiologic factors.