P.K. Sneed

A multi-institutional analysis of complication outcomes after arteriovenous malformation radiosurgery

PURPOSE To better understand radiation complications of arteriovenous malformation (AVM) radiosurgery and factors affecting their resolution. METHODS AND MATERIALS AVM patients (102/1255) who developed neurological sequelae after radiosurgery were studied. The median AVM marginal dose (Dmin) was 19 Gy (range: 10-35). The median volume was 5.7 cc (range: 0.26-143). Median follow-up was 34 months (range: 9-140). RESULTS Complications consisted of 80/102 patients with evidence of radiation injury to the brain parenchyma (7 also with cranial nerve deficits, 12 also with seizures, 5 with cyst formation), 12/102 patients with isolated cranial neuropathies, and 10/102 patients with only new or worsened seizures. Severity was classified as minimal in 39 patients, mild in 40, disabling in 21, and fatal in 2 patients. Symptoms resolved completely in 42 patients for an actuarial resolution rate of 54% +/- 7% at 3 years post-onset. Multivariate analysis identified significantly greater symptom resolution in patients with no prior history of hemorrhage (p = 0.01, 66% vs. 41%), and in patients with symptoms of minimal severity: headache or seizure as the only sequelae of radiosurgery (p < 0.0001, 88% vs. 34%). CONCLUSION Late sequelae of radiosurgery manifest in varied ways. Further long-term studies of these problems are needed that take into account symptom severity and prior hemorrhage history.

Diagnosis and Treatment of Recurrent High-Grade Astrocytoma

High-grade gliomas represent a significant source of cancer-related death, and usually recur despite treatment. In this analysis of current brain tumor medicine, we review diagnosis, standard treatment, and emerging therapies for recurrent astrocytomas. Difficulties in interpreting radiographic evidence, especially with regard to differentiating between tumor and necrosis, present a formidable challenge. The most accurate diagnoses come from tissue confirmation of recurrent tumor, but a combination of imaging techniques, such as magnetic resonance spectroscopy imaging, may also be relevant for diagnosis. Repeat resection can prolong life, but repeat irradiation of the brain poses serious risks and results in necrosis of healthy brain tissue; therefore, reirradiation is usually not offered to patients with recurrent tumors. We describe the use of conventional radiotherapy, intensity-modulated radiotherapy, brachytherapy, radiosurgery, and photodynamic therapy for recurrent high-grade glioma. The use of chemotherapy is limited by drug distribution and toxicity, but the development of new drug-delivery techniques such as convection-enhanced delivery, which delivers therapeutic molecules at an effective concentration directly to the brain, may provide a way to reduce systemic exposure to cytotoxic agents. We also discuss targeted therapies designed to inhibit aberrant cell-signaling pathways, as well as new experimental therapies such as immunotherapy. The treatment of this devastating disease has so far been met with limited success, but emerging knowledge of neuroscience and the development of novel therapeutic agents will likely give patients new options and require the neuro-oncology community to redefine clinical trial design and strategy continually.

Phase I/II trial of accelerated fractionation in brain metastases RTOG 85-28.

PURPOSE Radiation Therapy Oncology Group 85-28 represents a Phase I/II trial of accelerated fractionation in patients with brain metastases. METHODS AND MATERIALS Patients entered had controlled or absent primary with metastases other than brain which were stable or only brain metastases with the primary uncontrolled. Karnosfky status was required to be greater than 60. Patients received 1.6 Gy twice daily separated by 4-8 hr delivered 5 days a week. The entire brain was treated to 32.0 Gy and the boost dose escalated from 16.0 Gy to 22.40 Gy and subsequently 32.00 Gy and 42.40 Gy. RESULTS We observed no undue toxicity with escalating dose of irradiation. An incremental, although not statistically significant improvement in survival was noted with escalating doses. Median survival ranged from 4.2 months to 6.4 months with escalating dose of irradiation. Median survival also increased in patients with controlled primary tumors, non-lung primaries and solitary metastasis. CONCLUSION The incremental improvement in survival in patients with good prognostic factors appeared encouraging. The Radiation Therapy Oncology Group will test the 54.4 Gy study against 30 Gy in 2 weeks in a Phase III trial based on the results of this trial.

Interstitial irradiation and hyperthermia for the treatment of recurrent malignant brain tumors.

Between June 1987 and June 1989, 29 recurrent malignant gliomas or recurrent solitary brain metastases in 28 patients were treated in a Phase I study of interstitial irradiation and hyperthermia. Patient age ranged from 18 to 65 years, and the Karnofsky Performance Status scores ranged from 40 to 90%. There were 13 glioblastomas, 10 anaplastic astrocytomas, 3 melanomas, and 3 adenocarcinomas. Catheters were implanted stereotactically after computed tomography-based preplanning. Hyperthermia was administered before and after brachytherapy, using one to six 2450- or 915-MHz helical coil microwave antennas and one to three multisensor fiberoptic thermometry probes. The goal was to heat as much of the tumor as possible to 42.5 degrees C for 30 minutes. Within 30 minutes after the first hyperthermia treatment, implant catheters were afterloaded with high-activity iodine-125 seeds delivering tumor doses of 32.6 to 61.0 Gy. Most patients had no sensation of heating. Complications included seizures in 5 patients, reversible neurological changes in 9 patients, a scalp burn in 1, and infections in 3. Of 28 evaluable 2-month follow-up scans, 11 showed definite improvement in the radiological appearance of the tumor, 4 were slightly improved, 7 were stable, and 6 showed tumor progression. Ten patients underwent reoperation for persistent tumor and/or necrosis. Eleven of 28 patients are alive 40 to 97 weeks after treatment. Thirteen patients died of a brain tumor, 2 died of extracranial melanoma metastases, 1 died of new brain melanoma metastases, and 1 died of a pulmonary embolus. The median survival was 55 weeks overall. Median survival has not yet been reached for the anaplastic astrocytoma subgroup. We conclude that interstitial brain hyperthermia using helical coil microwave antennas is technically feasible. The level of toxicity is acceptable, and the computed tomographic response rate is encouraging.

Phase II and pharmacogenomics study of enzastaurin plus temozolomide during and following radiation therapy in patients with newly diagnosed glioblastoma multiforme and gliosarcoma

This open-label, single-arm, phase II study combined enzastaurin with temozolomide plus radiation therapy (RT) to treat glioblastoma multiforme (GBM) and gliosarcoma. Adults with newly diagnosed disease and Karnofsky performance status (KPS) ≥ 60 were enrolled. Treatment was started within 5 weeks after surgical diagnosis. RT consisted of 60 Gy over 6 weeks. Temozolomide was given at 75 mg/m(2) daily during RT and then adjuvantly at 200 mg/m(2) daily for 5 days, followed by a 23-day break. Enzastaurin was given once daily during RT and in the adjuvant period at 250 mg/day. Cycles were 28 days. The primary end point was overall survival (OS). Progression-free survival (PFS), toxicity, and correlations between efficacy and molecular markers analyzed from tumor tissue samples were also evaluated. A prospectively planned analysis compared OS and PFS of the current trial with outcomes from 3 historical phase II trials that combined novel agents with temozolomide plus RT in patients with GBM or gliosarcoma. Sixty-six patients were enrolled. The treatment regimen was well tolerated. OS (median, 74 weeks) and PFS (median, 36 weeks) results from the current trial were comparable to those from a prior phase II study using erlotinib and were significantly better than those from 2 other previous studies that used thalidomide or cis-retinoic acid, all in combination with temozolomide plus RT. A positive correlation between O-6-methylguanine-DNA methyltransferase promoter methylation and OS was observed. Adjusting for age and KPS, no other biomarker was associated with survival outcome. Correlation of relevant biomarkers with OS may be useful in future trials.

Stereotactic Radiosurgery and Interstitial Brachytherapy for Glial Neoplasms

The application of focal radiation therapies in the management of malignant gliomas has gone through a number of stages. Earlier efforts to improve local control of malignant gliomas involved the use of brachytherapy. Despite some early encouraging results, Phase 3 studies did not prove a significant survival benefit for the addition of brachytherapy for newly diagnosed glioblastoma. Most recently radiosurgery has been employed using the same rationale in that improved local control may improve survival. Results of the RTOG Phase 3 study are pending final publication, but early abstracted reports are negative. While radiosurgery and brachytherapy continue to be used as a form of therapy for selected patients with recurrent gliomas, new information from metabolic imaging studies suggests our problem with these techniques in part may be related to targeting. This paper reviews the recent literature and results of the use of brachytherapy and radiosurgery in the management of newly diagnosed and recurrent malignant gliomas.

Stereotactic radiosurgery in children.

The role of stereotactic radiosurgery in the treatment of pediatric patients is still being explored. We report the Gamma Knife treatment of 33 patients under the age of 21, at the University of California, San Francisco, between the years 1991 and 1993. Treatment-related toxicity has been low. 10/14 patients treated for arteriovenous malformation (AVM) with follow-up > 1 month have shown partial or complete AVM obliteration. No patient has had a new hemorrhage after AVM treatment. In children with malignant tumors, treatment was well tolerated, although most patients, ultimately, had progressive disease. Stereotactic radiosurgery is logistically possible in the pediatric population. Its use in selected patients with AVMs seems appropriate, although its role in the treatment of malignant brain tumors remains to be defined.

Brachytherapy of Brain Tumors

Temporary implants of high-activity 125iodine sources have been used in the treatment of brain tumors since December 1979 at the University of California, San Francisco. For previously untreated patients who underwent external beam radiation therapy followed by implant boost, median survival from the date of diagnosis was 88 weeks for 34 patients with glioblastoma multiforme (GM) and 157 weeks for 29 patients with nonglioblastoma gliomas (NGM). For recurrent tumors treated with brachytherapy only, median survival from the date of the implant was 54 weeks for 45 patients with GM and 81 weeks for 50 patients with NGM. Finally, in 48 patients with recurrent tumors treated with combined hyperthermia and brachytherapy, median survival from the date of the implant was 46 weeks for 25 patients with GM and 44 weeks for 7 patients with metastases; 18-month survival was 65% for 16 patients with NGM. Brachytherapy appears to be a useful technique for the treatment of selected recurrent brain tumors and selected primary glioblastomas.

SU‐D‐211‐04: Sector Intensity Modulated (SIM) Gamma Knife Stereotactic Radiosurgery

PURPOSE The latest Gamma Knife (GK) system, Perfexion, consists of 192 Co-60 sources divided into eight sectors. Treatment delivery includes multiple shots placed at different positions. For every shot, each sector can be either blocked or open with four different aperture sizes. However, the beam-on time is designed to be fixed. We proposed an innovative concept, Sector Intensity Modulated (SIM) Gamma Knife by dynamically varying the beam-on time for each individual sector to improve stereotactic radiosurgery planning quality. METHODS The anatomic structures and dose matrices from each sector for every shot were obtained from the GK workstation. The beam-on time for each sector was decomposed with various discrete levels and brute-force algorithm was used to get the optimal solution. The resulting SIM plan was then re-entered into the GK workstation. Six indices were used to benchmark the plan quality: Coverage, Conformality, Gradient, Maximum Dose(s) to critical structure(s), Volume receiving over 8 and 12 Gy. All the SIM plans in comparison with the original plans were further reviewed by an experienced oncologist. RESULTS The simulations were tested on various pituitary adenoma cases. Results consistently showed that SIM yielded better plans with all quantitative indices improved compared to original plan. It provides better conformality, quicker drop off of the isodose line outside the tumor, lower doses to the critical structures as optical- nerve/chiasm while maintaining at least 99% coverage of the tumor. Results were more favorable according to oncologists view. In particular, up to 20% or 0.6 cc volume decrease in healthy tissue receiving 8 Gy was observed. This may translate into clinically observable reduction in acute/late toxicities. CONCLUSIONS Our preliminary results show that Sector Intensity Modulated Gamma Knife offers superior treatment plans compared to the originally delivered plans. Further works as adding dynamic shot location and dynamic shot shaping will be discussed.

Radiation-induced Cavernous Malformation as a Late Sequelae of Stereotactic Radiosurgery for Epilepsy

Stereotactic radiosurgery (SRS) is a promising treatment for medically intractable mesial temporal lobe epilepsy. SRS for epilepsy has had an acceptable safety profile with reports of radiation-induced vascular malformations confined to central nervous system pathologies with prominent angiogenesis – namely, primary brain tumors, metastases, and arteriovenous malformations. Theoretical risks for radiation-induced lesions following radiosurgery for epilepsy have yet to be established. Of 13 patients treated in a pilot trial for medial temporal lobe epilepsy, one developed multiple delayed radiation-induced cavernous malformations following radiosurgery. This patient received a prescription dose of 20 Gy delivered to the amygdala, anterior hippocampus, and parahippocampal gyrus. Eight years following treatment, computed tomography imaging demonstrated an evolving hyperdensity in the mesial temporal lobe. Magnetic resonance imaging confirmed multiple T2 hypointense lesions with a mixed-signal intensity core in the left parahippocampal gyrus and anterior temporal lobe. The patient was initially managed conservatively. However, recurrent hemorrhage ultimately caused an acute deterioration in mental status, aphasia, and hemiparesis, necessitating surgical resection. Pathology confirmed radiation-induced cavernous malformations. This represents the first case of a radiation-induced vascular lesion as a long-term sequela of radiosurgery for epilepsy and illustrates the potential for this complication even when low doses are used in patients without angiogenic lesions. Optimal timing and indications for surgical resection of radiation-induced cavernous malformations prior to the development of neurologic symptoms warrant further refinement. Long-term vigilance and clinical monitoring are required.