Erin S. Murphy

Challenges With the Diagnosis and Treatment of Cerebral Radiation Necrosis

The incidence of radiation necrosis has increased secondary to greater use of combined modality therapy for brain tumors and stereotactic radiosurgery. Given that its characteristics on standard imaging are no different that tumor recurrence, it is difficult to diagnose without use of more sophisticated imaging and nuclear medicine scans, although the accuracy of such scans is controversial. Historically, treatment had been limited to steroids, hyperbaric oxygen, anticoagulants, and surgical resection. A recent prospective randomized study has confirmed the efficacy of bevacizumab in treating radiation necrosis. Novel therapies include using focused interstitial laser thermal therapy. This article will review the diagnosis and treatment of radiation necrosis.

RADIOTHERAPY FOR VESTIBULAR SCHWANNOMAS: A CRITICAL REVIEW

Vestibular schwannomas are slow-growing tumors of the myelin-forming cells that cover cranial nerve VIII. The treatment options for patients with vestibular schwannoma include active observation, surgical management, and radiotherapy. However, the optimal treatment choice remains controversial. We have reviewed the available data and summarized the radiotherapeutic options, including single-session stereotactic radiosurgery, fractionated conventional radiotherapy, fractionated stereotactic radiotherapy, and proton beam therapy. The comparisons of the various radiotherapy modalities have been based on single-institution experiences, which have shown excellent tumor control rates of 91-100%. Both stereotactic radiosurgery and fractionated stereotactic radiotherapy have successfully improved cranial nerve V and VII preservation to >95%. The mixed data regarding the ideal hearing preservation therapy, inherent biases in patient selection, and differences in outcome analysis have made the comparison across radiotherapeutic modalities difficult. Early experience using proton therapy for vestibular schwannoma treatment demonstrated local control rates of 84-100% but disappointing hearing preservation rates of 33-42%. Efforts to improve radiotherapy delivery will focus on refined dosimetry with the goal of reducing the dose to the critical structures. As future randomized trials are unlikely, we suggest regimented pre- and post-treatment assessments, including validated evaluations of cranial nerves V, VII, and VIII, and quality of life assessments with long-term prospective follow-up. The results from such trials will enhance the understanding of therapy outcomes and improve our ability to inform patients.

Long-term outcomes of Gamma Knife radiosurgery in patients with vestibular schwannomas

OBJECT The authors sought to determine the long-term tumor control and side effects of Gamma Knife radiosurgery (GKRS) in patients with vestibular schwannomas (VS). METHODS One hundred seventeen patients with VS underwent GKRS between January 1997 and February 2003. At the time of analysis, at least 5 years had passed since GKRS in all patients. The mean patient age was 60.9 years. The mean maximal tumor diameter was 1.77 ± 0.71 cm. The mean tumor volume was 1.95 ± 2.42 ml. Eighty-two percent of lesions received 1300 cGy and 14% received 1200 cGy. The median dose homogeneity ratio was 1.97 and the median dose conformality ratio was 1.78. Follow-up included MR imaging or CT scanning approximately every 6-12 months. Rates of progression to surgery were calculated using the Kaplan-Meier method. RESULTS Of the 117 patients in whom data were analyzed, 103 had follow-up MR or CT images and 14 patients were lost to follow-up. Fifty-three percent of patients had stable tumors and 37.9% had a radiographically documented response. Imaging-documented tumor progression was present in 8 patients (7.8%), but in 3 of these the lesion eventually stabilized. Only 5 patients required a neurosurgical intervention. The estimated 1-, 3-, and 5-year rates of progression to surgery were 1, 4.6, and 8.9%, respectively. One patient (1%) developed trigeminal neuropathy, 4 patients (5%) developed permanent facial neuropathy, 3 patients (4%) reported vertigo, and 7 patients (18%) had new gait imbalance following GKRS. CONCLUSIONS Gamma Knife radiosurgery results in excellent local control rates with minimal toxicity for patients with VS. The authors recommend standardized follow-up to gain a better understanding of the long-term effects of GKRS.

Necrosis after craniospinal irradiation: results from a prospective series of children with central nervous system embryonal tumors.

PURPOSE Necrosis of the central nervous system (CNS) is a known complication of craniospinal irradiation (CSI) in children with medulloblastoma and similar tumors. We reviewed the incidence of necrosis in our prospective treatment series. PATIENTS AND METHODS Between 1996 and 2009, 236 children with medulloblastoma (n = 185) or other CNS embryonal tumors (n = 51) received postoperative CSI followed by dose-intense cyclophosphamide, vincristine, and cisplatin. Average risk cases (n = 148) received 23.4 Gy CSI, 36 Gy to the posterior fossa, and 55.8 Gy to the primary; after 2003, the treatment was 23.4 Gy CSI and 55.8 Gy to the primary. All high-risk cases (n = 88) received 36-39.6 Gy CSI and 55.8 Gy primary. The primary site clinical target volume margin was 2 cm (pre-2003) or 1 cm (post-2003). With competing risk of death by any cause, we determined the cumulative incidence of necrosis. RESULTS With a median follow-up of 52 months (range, 4-163 months), eight cases of necrosis were documented. One death was attributed. The median time to the imaging evidence was 4.8 months and to symptoms 6.0 months. The cumulative incidence at 5 years was 3.7% ± 1.3% (n = 236) for the entire cohort and 4.4% ± 1.5% (n = 196) for infratentorial tumor location. The mean relative volume of infratentorial brain receiving high-dose irradiation was significantly greater for patients with necrosis than for those without: ≥ 50 Gy (92.12% ± 4.58% vs 72.89% ± 1.96%; P=.0337), ≥ 52 Gy (88.95% ± 5.50% vs 69.16% ± 1.97%; P=.0275), and ≥ 54 Gy (82.28% ± 7.06% vs 63.37% ± 1.96%; P=.0488), respectively. CONCLUSIONS Necrosis in patients with CNS embryonal tumors is uncommon. When competing risks are considered, the incidence is 3.7% at 5 years. The volume of infratentorial brain receiving greater than 50, 52, and 54 Gy, respectively, is predictive for necrosis.

Review of cranial radiotherapy-induced vasculopathy

Cranial radiation can impact the cerebral vasculature in many ways, with a wide range of clinical manifestations. The incidence of these late effects including cerebrovascular accidents (CVAs), lacunar lesions, vascular occlusive disease including moyamoya syndrome, vascular malformations, and hemorrhage is not well known. This article reviews the preclinical findings regarding the pathophysiology of late radiation-induced vascular damage, and discusses the clinical incidence and risk factors for each type of vasculopathy. The pathophysiology is complex and dependent on the targeted blood vessels, and upregulation of pro-inflammatory and hypoxia-related genes. The risk factors for adult CVAs are similar to those for patients not exposed to cranial radiotherapy. For children, risks for late vascular complications include young age at radiotherapy, radiotherapy dose, NF1, tumor location, chemotherapy, and endocrine abnormalities. The incidence of late vascular complications of radiotherapy may be impacted by improved technology, therapeutic interventions, and appropriate follow up.

Treatment of cerebral radiation necrosis with bevacizumab: the Cleveland clinic experience.

Background:Cerebral radiation necrosis (RN) is a devastating complication of radiation therapy for brain tumors. Recent studies have explored the role of bevacizumab, a humanized monoclonal antibody directed against vascular endothelial growth factor in the treatment of RN of the brain. We report 24 patients with cerebral RN who were treated with bevacizumab. Materials and Methods:Twenty-four patients diagnosed with cerebral RN and treated with different schedules of bevacizumab between July 2007 and June 2012, were identified from the Cleveland Clinic Brain Tumor and Neuro-Oncology Center’s database. Pretreatment and posttreatment magnetic resonance imaging (MRI) studies were compared to evaluate bevacizumab efficacy. Results:Posttreatment MRI demonstrated a radiographic improvement in 23 of 24 patients on the postcontrast T1-weighted MRI and fluid-attenuated inversion-recovery sequences. Using the McDonald criteria, the average change in the T1-weighted postcontrast MRI was a decrease of 48.1%, and the average change in the fluid-attenuated inversion-recovery images was a decrease of 53.7%. There was a mean daily dose reduction of 9.4 mg of dexamethasone after initiation of bevacizumab in patients who were on steroids at the start of bevaciuzmab therapy for RN. Treatment with bevacizumab was well tolerated with only 1 grade 3 adverse event. Conclusions:The current study demonstrates that bevacizumab treatment results in excellent clinical and radiologic response in patients with RN caused by common forms of radiation therapy. The safety profile of bevacizumab use in RN is acceptable. In the current study, we found no difference between different schedules of bevacizumab in treatment outcomes.

Impact of the radiosurgery prescription dose on the local control of small (2 cm or smaller) brain metastases

OBJECTIVE The impact of the stereotactic radiosurgery (SRS) prescription dose (PD) on local progression and radiation necrosis for small (≤ 2 cm) brain metastases was evaluated. METHODS An institutional review board-approved retrospective review was performed on 896 patients with brain metastases ≤ 2 cm (3034 tumors) who were treated with 1229 SRS procedures between 2000 and 2012. Local progression and/or radiation necrosis were the primary end points. Each tumor was followed from the date of radiosurgery until one of the end points was reached or the last MRI follow-up. Various criteria were used to differentiate tumor progression and radiation necrosis, including the evaluation of serial MRIs, cerebral blood volume on perfusion MR, FDG-PET scans, and, in some cases, surgical pathology. The median radiographic follow-up per lesion was 6.2 months. RESULTS The median patient age was 56 years, and 56% of the patients were female. The most common primary pathology was non-small cell lung cancer (44%), followed by breast cancer (19%), renal cell carcinoma (14%), melanoma (11%), and small cell lung cancer (5%). The median tumor volume and median largest diameter were 0.16 cm3 and 0.8 cm, respectively. In total, 1018 lesions (34%) were larger than 1 cm in maximum diameter. The PD for 2410 tumors (80%) was 24 Gy, for 408 tumors (13%) it was 19 to 23 Gy, and for 216 tumors (7%) it was 15 to 18 Gy. In total, 87 patients (10%) had local progression of 104 tumors (3%), and 148 patients (17%) had at least radiographic evidence of radiation necrosis involving 199 tumors (7%; 4% were symptomatic). Univariate and multivariate analyses were performed for local progression and radiation necrosis. For local progression, tumors less than 1 cm (subhazard ratio [SHR] 2.32; p < 0.001), PD of 24 Gy (SHR 1.84; p = 0.01), and additional whole-brain radiation therapy (SHR 2.53; p = 0.001) were independently associated with better outcome. For the development of radiographic radiation necrosis, independent prognostic factors included size greater than 1 cm (SHR 2.13; p < 0.001), location in the corpus callosum (SHR 5.72; p < 0.001), and uncommon pathologies (SHR 1.65; p = 0.05). Size (SHR 4.78; p < 0.001) and location (SHR 7.62; p < 0.001)-but not uncommon pathologies-were independent prognostic factors for the subgroup with symptomatic radiation necrosis. CONCLUSIONS A PD of 24 Gy results in significantly better local control of metastases measuring < 2 cm than lower doses. In addition, tumor size is an independent prognostic factor for both local progression and radiation necrosis. Some tumor pathologies and locations may also contribute to an increased risk of radiation necrosis.

Radiosurgery for Pediatric Brain Tumors

The utility of radiosurgery for pediatric brain tumors is not well known. For children, radiosurgery may have an important role for treating unresectable tumors, residual disease, or tumors in the recurrent setting that have received prior radiotherapy. The available evidence demonstrates utility for some children with primary brain tumors resulting in good local control. Radiosurgery can be considered for limited residual disease or focal recurrences. However, the potential toxicities are unique and not insignificant. Therefore, prospective studies need to be performed to develop guidelines for indications and treatment for children and reduce toxicity in this population.

Overall survival and the response to radiotherapy among molecular subtypes of breast cancer brain metastases treated with targeted therapies

The current study was conducted to investigate survival and the response to radiotherapy among patients with molecular subtypes of breast cancer brain metastases treated with or without targeted therapies.

Treatment of Large Brain Metastases With Stereotactic Radiosurgery

Introduction: We report our series of patients with large brain metastases, >3 cm in diameter, who received stereotactic radiosurgery (SRS) as a component of their treatment, focusing on survival and intracranial recurrence rates. Materials and Methods: The brain tumor database was queried for patients treated with SRS for large brain metastases. Local recurrence (LR) and distant brain recurrence (DBR) rates were calculated using cumulative incidence analysis, and overall survival (OS) was calculated using Kaplan-Meier analysis. Patients were classified into 1 of the 4 groups based on treatment strategy: SRS alone, surgery plus SRS, SRS plus whole-brain radiation therapy (WBRT), and salvage SRS from more remote WBRT and/or surgery. Results: A total of 153 patients with 164 lesions were evaluated. The SRS alone was the treatment approach in 62 lesions, surgery followed by SRS to the resection bed (S + SRS) in 33, SRS + WBRT in 19, and salvage SRS in 50. There was no statistically significant difference in OS between the 4 treatment groups (P = .06). Median survival was highest in patients receiving surgery + SRS (12.2 months) followed by SRS + WBRT (6.9 months), SRS alone (6.6 months), and salvage SRS (6.1 months). There was also no significant difference for LR rates between the groups at 12 months. No significant variables on univariate analysis were noted for LR. The 12-month DBR rates were highest in the S + SRS group (52%), followed by salvage SRS (31%), SRS alone (28%), and SRS + WBRT (13%; P = .03). Conclusion: There were no significant predictors for local control. Keeping in mind that patient numbers in the SRS + WBRT group are small, the addition of WBRT to SRS did not appear to significantly improve survival or local control, supporting the delayed use of WBRT for some patients to prevent potential side effects provided regular imaging surveillance and salvage therapy are utilized. Prospective studies are needed to optimize SRS treatment regimens for patients with large brain metastases.