Dosimetric differences between cesium-131 and iodine-125 brachytherapy for the treatment of resected brain metastases

Purpose: To compare treatment plans and evaluate dosimetric characteristics of permanent cesium-131 (131Cs) vs. iodine-125 (125I) implants used in brain brachytherapy. Material and methods: Twenty-four patients with 131Cs implants from a prospective phase I/II trial were re-planned with 125I implants. In order to evaluate the volume of brain tissue exposed to radiation therapy (RT), the dose volume histogram was generated for both radioisotopes. To evaluate the dosimetric differences of the two radioisotopes we compared homogeneity (HI) and conformity indices (CI), and dose covering 100% (D100), 90% (D90), 80% (D80), and 50% (D50) of the clinical target volume (CTV). Results: At the 100%, 90%, 80%, and 50% isodose lines, the 131Cs plans exposed less mean volume of brain tissue than the 125I plans (p \u3c 0.001). The D100, D90, D80, and D50 were smaller for 131Cs (p \u3c 0.001). The HI and CI for 131Cs vs. 125I were 19.71 vs. 29.04 and 1.31 vs. 1.92, respectively (p \u3c 0.001). Conclusions: Compared to 125I, 131Cs exposed smaller volumes of brain tissue to equivalent doses of radiation and delivered lower radiation doses to equivalent volumes of the CTV. 131Cs exhibited a higher HI, indicating increased uniformity of doses within the CTV. Lastly, 131Cs presented a CI closer to 1, indicating that the total volume receiving the prescription dose was closer to the desired CTV volume. These results suggest that 131Cs is dosimetrically superior to 125I and may explain the reason for the 0% incidence of radiation necrosis (RN) in our previously published prospective study using 131Cs

Feasibility and safety of GliaSite brachytherapy in treatment of CNS tumors following neurosurgical resection

Purpose: To investigate feasibility and safety of GliaSite brachytherapy for treatment of central nervous system (CNS) tumors following neurosurgical resection. We report mature results of long-term follow-up, outcomes and toxicity. Materials and Methods: In the period from 2004 to 2007, 10 consecutive adult patients with recurrent, newly diagnosed, and metastatic brain malignancies underwent GliaSite brachytherapy following maximally safe neurosurgical resection. While 6/10 (60%) patients were treated for recurrence, having previously been treated with external beam radiotherapy (EBRT), 4/10 (40%) received radiotherapy (RT) for the first time. A median dose of 52.0 Gy (range, 45.0 - 60.0 Gy) was prescribed to 0.5 cm - 1.0 cm from the balloon surface. Radiation Therapy Oncology Group (RTOG) criteria were used to assess toxicities associated with this technique. Follow-up was assessed with MRI scans and was available on all enrolled patients. Results: Median follow-up was 38 months (range, 18 - 57 months). Mean size of GliaSite balloon was 3.4 cm (range, 2.0 - 4.0 cm). Median survival was 14.0 months for the entire cohort after the treatment. The 17.6 and 16.0 months average survival for newly diagnosed and recurrent high grade gliomas (HGG), respectively, translated into a three-month improvement in survival in patients with newly diagnosed HGG compared to historical controls (P = 0.033). There were no RTOG grades 3 or 4 acute or late toxicities. Follow-up magnetic resonance imaging (MRI) imaging did not identify radiation necrosis. Conclusions: Our data indicate that treatment with GliaSite brachytherapy is feasible, safe and renders acceptable local control, acute and long-term toxicities. We are embarking on testing larger numbers of patients with this treatment modality

Assessment of Epidermal Growth Factor Receptor (EGFR) expression in human meningioma

<p>Abstract</p> <p>Purpose</p> <p>This study explores whether meningioma expresses epidermal growth factor receptor (EGFR) and determines if there is a correlation between the WHO grade of this tumor and the degree of EGFR expression.</p> <p>Methods</p> <p>Following institutional review board approval, 113 meningioma specimens from 89 patients were chosen. Of these, 85 were used for final analysis. After a blinded review, immunohistochemical stains for EGFR were performed. Staining intensity (SI) was scored on a scale 0-3 (from no staining to strong staining). Staining percentage of immunoreactive cells (SP) was scored 1-5 (from the least to the maximum percent of the specimen staining). Immunohistochemical score (IHS) was calculated as the product of SI and SP.</p> <p>Results</p> <p>Eighty-five samples of meningioma were classified in accordance with World Health Organization (WHO) criteria: benign 57/85 (67%), atypical 23/85 (27%), and malignant 5/85 (6%). The majority of samples demonstrated a moderate SI for EGFR. IHS for EGFR demonstrated a significant association between SI and histopathologic subtype. Also, there was a correlation between the SP and histopathologic subtype (p = 0.029). A significant association was determined when the benign and the atypical samples were compared to the malignant with respect to the SP (p = 0.009). While there was a range of the IHS for the benign and the atypical histologic subtypes, malignant tumors exhibited the lowest score and were statistically different from the benign and the atypical specimens (p < 0.001).</p> <p>Conclusions</p> <p>To our knowledge, this represents the largest series of meningioma samples analyzed for EGFR expression reported in the literature. EGFR expression is greatest in benign meningiomas and may serve a potential target for therapeutic intervention with selective EGFR inhibitors.</p

Advances in Radiotherapy for Glioblastoma

External beam radiotherapy (RT) has long played a crucial role in the treatment of glioblastoma. Over the past several decades, significant advances in RT treatment and image-guidance technology have led to enormous improvements in the ability to optimize definitive and salvage treatments. This review highlights several of the latest developments and controversies related to RT, including the treatment of elderly patients, who continue to be a fragile and vulnerable population; potential salvage options for recurrent disease including reirradiation with chemotherapy; the latest imaging techniques allowing for more accurate and precise delineation of treatment volumes to maximize the therapeutic ratio of conformal RT; the ongoing preclinical and clinical data regarding the combination of immunotherapy with RT; and the increasing evidence of cancer stem-cell niches in the subventricular zone which may provide a potential target for local therapies. Finally, continued development on many fronts have allowed for modestly improved outcomes while at the same time limiting toxicity