F. Zorlu1, M. Gurkaynak1, U. Selek1, S. Ulger1, A. Turker2, A. Kars2. 1Hacettepe University Oncology Hospital, Radiation Oncology Department, Ankara, Turkey, ...
Proceedings of the 50th Annual ASTRO Meeting
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A Comparison of Helical Tomotherapy (HT), Fixed-field Intensity-modulated Radiotherapy (IMRT) and 3D Conformal Radiotherapy (3DCRT) Plans in Stereotactic Radiation Therapy of Skull Base Meningioma
H. S. Elhateer, R. Ruo, T. Muanza, D. Roberge, C. Lambert, L. Souhami, G. Shenouda McGill University, Montreal, QC, Canada Purpose/Objective(s): To assess the potential benefits and limitations of IMRT in the treatment of skull base meningioma. Materials/Methods: We undertook a retrospective treatment planning study using the CT simulation data for 8 patients with meningiomas of the skull base originally treated with fractionated stereotactic radiotherapy. Target volumes and organs at risk were delineated with the help of co-registered MRI images. A 3 mm margin was added to the gross tumor volume to create the planning target volume (PTV). Treatment plans were generated for non-coplanar 3DCRT, coplanar fixed-field IMRT (7-9 fields) and Helical Tomotherapy (HT) to deliver a total dose of 52.2 Gy in 1.8 Gy fractions. The treatment goals were to cover $95% and 99% of the PTV with 100% and $95% of the prescribed dose , respectively, whilst keeping the maximum point dose to optic nerves, chiasm and brain stem #54 Gy. Based on review by experienced radiation oncologist, a clinically accepted plan from each modality was selected for comparison. The parameters used for comparison were the ability of each plan to achieve the predetermined treatment goals along with the conformity index (CI), homogeneity index (HI), and target coverage index (Cov. I). Direct comparison of the DVH data for the PTV coverage and OAR sparing was done along with the repeated measures ANOVA with Tukey’s multiple comparison post hoc tests for CI, HI, and Cov. I comparison. Results: The eight meningiomas of the skull base (6 cavernous sinus, 1 suprasellar, and 1 olfactory groove tumors) had a median PTV of 20.3 cc (range, 7.4-50.7 cc). The PTV coverage goals has been achieved in all HT plans, compared to 7 and 6 plans for fixed-field IMRT and 3DCRT , respectively, with 1-1.5% of the PTV missing the goals by 1-3% of the prescribed dose. The PTV coverage index for HT plans was significantly higher compared to fixed-field IMRT (p = 0.004), with no significant difference between either HT and 3DCRT or fixed-field IMRT and 3DCRT. The HT plans achieved the highest HI followed by fixed-field IMRT then 3DCRT (p = 0.002). In contrast, 3DCRT plans had higher CI than both IMRT modalities (p \ 0.001). The treatment goals for the optic chiasm and optic nerves were achieved in all IMRT plans while it has been violated in 5 3DCRT (by 0.8-1.2 Gy). The treatment goal for the brainstem was achieved in all plans with no significant differences. Conclusions: When treating base of skull meningiomas, HT resulted in the best target coverage and dose homogeneity. When compared to 3DCRT, sparing of organs at risk was improved with either HT or fixed-field IMRT at the expense of a lower CI. Author Disclosure: H.S. Elhateer, None; R. Ruo, None; T. Muanza, None; D. Roberge, None; C. Lambert, None; L. Souhami, None; G. Shenouda, None.
2147
Radiotherapy with Concomitant Temozolomide in WHO Grade III Glial Tumors
F. Zorlu1, M. Gurkaynak1, U. Selek1, S. Ulger1, A. Turker2, A. Kars2 1 Hacettepe University Oncology Hospital, Radiation Oncology Department, Ankara, Turkey, 2Hacettepe University Oncology Hospital, Medical Oncology Division, Ankara, Turkey
Purpose/Objective(s): Concomitant chemoradiotherapy with Temozolomide (CRT) is the current standard for glioblastoma multiforme. As CRT literature is evolving for Grade III glial tumors, here we present our experience in Grade III glial tumors. Materials/Methods: Twenty-five patients with Grade III glial tumors treated between November 2003 and March 2007 in our center were evaluated. Inclusion criteria required histopathologic diagnosis, normal creatinine clearance, liver enzymes, and blood count. Exclusion criteria were age over 60-years-old and KPS less than 70. The 3DCRT was a total of 60 Gy (2 Gy/fractions/day) and initial CTV was based on a 2-cm margin on GTV in T1 postcontrast MRI images rather than on peritumoral edema to 40 Gy and 20 Gy boost was applied with CTV of 1 cm. Concomitant Temozolomide was prescribed with two schedules: 150 mg/m2 /day in 5 days in each cycle in the first and fifth weeks of radiotherapy (protocol week 1 and 5) and 75 mg/m2 /day given 7 days per week from the first to last day of RT (protocol daily). Ten patients in protocol week 1 and 5 and 15 in protocol daily were treated. Results: Grade III histopathology was as follows; astrocytoma, 15; mixed-oligoastrocytoma, 5; and oligodendroglioma 5. Median age was 40 (range, 19-56 years) and median KPS were 90 (range, 80-100). Surgical excision was gross total in 24 patients, and only biopsy in 1 patient. Median follow-up period was 15.4 months (range, 3 -42 months) after CRT. No acute Grade 3-4 toxicity was recorded for radiotherapy and chemotherapy. Eleven patients had local progression/recurrence and successful salvage was only possible in 3 (2 resection, 1 reirradiation with CyberKnife) while other 8 died following second-line chemotherapy. Fourteen patients are radiological and clinical progression-free on last follow-up (astrocytoma, 7 alive/15; oligodendrogliomas, 3 alive/5; mixed- oligoastrocytoma, 4 alive/ 5 patients). Progression-free survival (PFS) was 62.4% (SE 10.6%) and 42.8% (SE 11.9%) at 1 and 2 year, respectively. Median progression-free survival was 19.6 months. Overall survival (OS) was 86.1% (SE 7.6%) and 61.8% (SE 11.7%) at 1 and 2 year, respectively. Concomitant chemotherapy protocol did not significantly affect PFS or OS. Two-year overall survival for Grade III astrocytoma, Grade III oligodendroglioma, Grade III oligoastrocytoma were as follows: 51.3% (SE 16.6%), 66.7% (SE 27.2%), and 80% (SE 17.9%), respectively. No prognostic factor was found significant in univariate and multivariate analysis for survival. Conclusions: Radiotherapy with concomitant Temozolomide was well-tolerated in our limited number cohort with no apparent superior outcome in comparison to literature with radiotherapy alone series. Long-term follow-up will highlight the final outcome. Author Disclosure: F. Zorlu, None; M. Gurkaynak, None; U. Selek, None; S. Ulger, None; A. Turker, None; A. Kars, None.
2148
Stereotactic Radiosurgery with or without Whole Brain Radiotherapy for Patients with a Single Radioresistant Brain Metastasis
J. W. Clarke, J. McGregor, J. C. Grecula, N. A. Mayr, J. Z. Wang, K. Li, N. Gupta, R. Cavaliere, S. Register, S. S. Lo Arthur G. James Cancer Hospital, The Ohio State University Medical Center, Columbus, OH Purpose/Objective(s): To examine the outcomes of patients with a single brain metastasis from radioresistant histologies (renal cell carcinoma and melanoma) treated with stereotactic radiosurgery (SRS) with or without whole-brain radiotherapy (WBRT).
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