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Evaluation of Hippocampal Dose for Patients Undergoing Intensity Modulated Radiotherapy for Nasopharyngeal Cancer
I. J. Radiation Oncology d Biology d Physics
S508
2622
Volume 81, Number 2, Supplement, 2011
Evaluation of Hippocampal Dose for Patients Undergoing Intensity Modulated Radiotherapy for Nasopharyngeal Cancer
B. Khodayari, S. Stanic, O. H. Wooten, A. Dublin, J. A. Purdy, A. M. Chen University of California Davis, Sacramento, CA Purpose/Objective(s): The proximity of the nasopharynx to the medial temporal lobe may place nasopharyngeal carcinoma patients at relatively high risk of radiation-induced injury to the hippocampus if treated with intensity-modulated radiotherapy (IMRT). Due to the importance of the HPC with respect to memory and cognitive functioning, the objective of this study was to evaluate the dose to the HPC among patients undergoing IMRT for this disease. Materials/Methods: Five patients with biopsy-proven, locally advanced nasopharyngeal cancer comprised the study population. Total prescribed dose to the planning target volume (PTV) was 70 Gy (D95%)delivered in 2.12 Gy daily fractions using IMRT for all patients. For each patient, the HPC was retrospectively delineated on axial images from computed tomography obtained at the time of simulation. Using established anatomical guidelines, MRI co-registration, and the assistance of a board certified neuroradiologist, the right and left HPC was contoured beginning at the most anterior portion of the lateral ventricle, where the medial, lateral and anterior portions of the HPC were identified. Superior boundaries of the HPC consisted of the most medial region of the temporal lobe. Inferior boundaries of the HPC were defined at the level of the pons and pituitary gland. IMRT treatment plans were generated without dose-volume constraints to the HPC. A range of dose-volume statistics for each patient’s HPC was calculated. Results: The mean HPC volume ranged from 3.4 to 4.0 cm3 (median, 3.78 cm3). The average maximum dose to the HPC was 52.5 Gy (range, 35.6 to 74.1 Gy) and the average mean dose was 28.3 Gy (range, 20.2 to 48.0 Gy). The mean volume of the HPC receiving at least 40 Gy, 50 Gy, and 60 Gy was 21.0 ± 29.7% (range, 0 - 72%), 8.6 ± 14.3 % (range, 0 - 33%), and 5.5 ± 9.1% (range, 0 - 21%), respectively. Conclusions: Our dosimetric analysis suggests that for patients undergoing IMRT for nasopharyngeal cancer, the HPC routinely receives significantly high doses. Given the improved long-term survival of these patients, our current policy is to contour the HPC as a critical organ at risk. A prospective trial incorporating neurocognitive testing is under design. Author Disclosure: B. Khodayari: None. S. Stanic: None. O.H. Wooten: None. A. Dublin: None. J.A. Purdy: None. A.M. Chen: None.
2623
The Study of Dosimetry Comparison between Volumetric Modulated Arc Therapy with RapidArc and Fixed Field Dynamic IMRT for Local-Regionally Advanced Nasopharyngeal Carcinoma
S. Yan Beijing Cancer Hospital, Beijing 100142, China Purpose/Objective(s): A dosimetric study was performed to evaluate the performance of volumetric modulated arc radiotherapy with RapidArc on locally advanced nasopharyngeal carcinoma (NPC). Materials/Methods: The CT scan data sets of 20 patients of locally advanced NPC were selected randomly. The plans were managed using volumetric modulated arc with RapidArc and fixed nine-field coplanar dynamic intensity-modulated Radiotherapy (IMRT) for these patients, respectively. The dosimetry of the planning target volumes (PTV), the organs at risk (OARs) and the healthy tissue was evaluated. The dose prescription was set to 70Gy to the primary tumor and 60Gy to the clinical target volumes (CTV) in 33 fractions. Each fraction applied daily, five fractions per week. The monitor units (MU) values and the delivery time were scored to evaluate the expected treatment efficiency. Results: Both techniques had reached clinical treatment’s requirement. The mean dose (Dmean), maximum dose (Dmax) and minimum dose (Dmin) in RapidArc and fixed field IMRT for PTV were 68.4 ± 0.6Gy, 74.8 ± 0.9Gy and 56.8 ± 1.1Gy; 67.6 ± 0.6Gy, 73.8 ± 0.4Gy and 57.5 ± 0.6Gy (p\0.05), respectively. Homogeneity index was 78.85 ± 1.29 in RapidArc and 80.34 ± 0.54 (p\0.05) in IMRT. The conformity index (CI: 95%) was 0.78 ± 0.01 for both techniques(p.0.05). Comparing to IMRT, RapidArc allowed a reduction of Dmean to the brain stem, mandible, optic nerves of 14.1%(p\0.05), 5.6%(p\0.05)and 12.2%(p\0.05), respectively. For the healthy tissue and the whole absorbed dose, Dmean of RapidArc was reduced by 3.6%(p\0.05), 3.7%(p\0.05), respectively. The mean dose to the parotids, the spinal cord and lens has no statistical difference between them. The mean MU value of RapidArc and IMRT was 550 and 1379;The mean treatment time of RapidArc and IMRT was 165s and 447s .Compared to IMRT, the delivery time and the MU value of RapidArc were reduced by 63% and 60% respectively. Conclusions: For locally advanced NPC, both RapidArc and IMRT reached the clinic requirement. The target volume coverage was similar for the different techniques. The RapidArc technique showed some improvements in organs at risk and other tissue sparing while using reduced monitor units and delivery time. Author Disclosure: S. Yan: None.
2624
Three-Dimensional Conformal Radiation Therapy in the Salvage of 212 Locally Recurrent Nasopharyngeal Carcinoma Cases
S. F. Qiu1,2, J. D. J. Lu1, S. J. Lin3, I. W. K. Tham1, J. Lu4, J. J. Pan3 1 National University Cancer Institute Singapore, Singapore 119228, Singapore, 2Department of Radiation Oncology, Cancer Hospital of Fujian Medical University, Fuzhou, China, 3Department of Radiation Oncology, Cancer Hospital of Fujian Medical University, Fuzhou, China, 4of Radiation Oncology, Cancer Hospital of Fujian Medical University, Fuzhou, China
Purpose/Objective(s): Local recurrences of nasopharyngeal carcinoma (NPC) may be salvaged by re-irradiation using conventional techniques, but with significant morbidity. Three-dimensional conformal radiation therapy (3D-CRT) including intensity
S508
2622
Volume 81, Number 2, Supplement, 2011
Evaluation of Hippocampal Dose for Patients Undergoing Intensity Modulated Radiotherapy for Nasopharyngeal Cancer
B. Khodayari, S. Stanic, O. H. Wooten, A. Dublin, J. A. Purdy, A. M. Chen University of California Davis, Sacramento, CA Purpose/Objective(s): The proximity of the nasopharynx to the medial temporal lobe may place nasopharyngeal carcinoma patients at relatively high risk of radiation-induced injury to the hippocampus if treated with intensity-modulated radiotherapy (IMRT). Due to the importance of the HPC with respect to memory and cognitive functioning, the objective of this study was to evaluate the dose to the HPC among patients undergoing IMRT for this disease. Materials/Methods: Five patients with biopsy-proven, locally advanced nasopharyngeal cancer comprised the study population. Total prescribed dose to the planning target volume (PTV) was 70 Gy (D95%)delivered in 2.12 Gy daily fractions using IMRT for all patients. For each patient, the HPC was retrospectively delineated on axial images from computed tomography obtained at the time of simulation. Using established anatomical guidelines, MRI co-registration, and the assistance of a board certified neuroradiologist, the right and left HPC was contoured beginning at the most anterior portion of the lateral ventricle, where the medial, lateral and anterior portions of the HPC were identified. Superior boundaries of the HPC consisted of the most medial region of the temporal lobe. Inferior boundaries of the HPC were defined at the level of the pons and pituitary gland. IMRT treatment plans were generated without dose-volume constraints to the HPC. A range of dose-volume statistics for each patient’s HPC was calculated. Results: The mean HPC volume ranged from 3.4 to 4.0 cm3 (median, 3.78 cm3). The average maximum dose to the HPC was 52.5 Gy (range, 35.6 to 74.1 Gy) and the average mean dose was 28.3 Gy (range, 20.2 to 48.0 Gy). The mean volume of the HPC receiving at least 40 Gy, 50 Gy, and 60 Gy was 21.0 ± 29.7% (range, 0 - 72%), 8.6 ± 14.3 % (range, 0 - 33%), and 5.5 ± 9.1% (range, 0 - 21%), respectively. Conclusions: Our dosimetric analysis suggests that for patients undergoing IMRT for nasopharyngeal cancer, the HPC routinely receives significantly high doses. Given the improved long-term survival of these patients, our current policy is to contour the HPC as a critical organ at risk. A prospective trial incorporating neurocognitive testing is under design. Author Disclosure: B. Khodayari: None. S. Stanic: None. O.H. Wooten: None. A. Dublin: None. J.A. Purdy: None. A.M. Chen: None.
2623
The Study of Dosimetry Comparison between Volumetric Modulated Arc Therapy with RapidArc and Fixed Field Dynamic IMRT for Local-Regionally Advanced Nasopharyngeal Carcinoma
S. Yan Beijing Cancer Hospital, Beijing 100142, China Purpose/Objective(s): A dosimetric study was performed to evaluate the performance of volumetric modulated arc radiotherapy with RapidArc on locally advanced nasopharyngeal carcinoma (NPC). Materials/Methods: The CT scan data sets of 20 patients of locally advanced NPC were selected randomly. The plans were managed using volumetric modulated arc with RapidArc and fixed nine-field coplanar dynamic intensity-modulated Radiotherapy (IMRT) for these patients, respectively. The dosimetry of the planning target volumes (PTV), the organs at risk (OARs) and the healthy tissue was evaluated. The dose prescription was set to 70Gy to the primary tumor and 60Gy to the clinical target volumes (CTV) in 33 fractions. Each fraction applied daily, five fractions per week. The monitor units (MU) values and the delivery time were scored to evaluate the expected treatment efficiency. Results: Both techniques had reached clinical treatment’s requirement. The mean dose (Dmean), maximum dose (Dmax) and minimum dose (Dmin) in RapidArc and fixed field IMRT for PTV were 68.4 ± 0.6Gy, 74.8 ± 0.9Gy and 56.8 ± 1.1Gy; 67.6 ± 0.6Gy, 73.8 ± 0.4Gy and 57.5 ± 0.6Gy (p\0.05), respectively. Homogeneity index was 78.85 ± 1.29 in RapidArc and 80.34 ± 0.54 (p\0.05) in IMRT. The conformity index (CI: 95%) was 0.78 ± 0.01 for both techniques(p.0.05). Comparing to IMRT, RapidArc allowed a reduction of Dmean to the brain stem, mandible, optic nerves of 14.1%(p\0.05), 5.6%(p\0.05)and 12.2%(p\0.05), respectively. For the healthy tissue and the whole absorbed dose, Dmean of RapidArc was reduced by 3.6%(p\0.05), 3.7%(p\0.05), respectively. The mean dose to the parotids, the spinal cord and lens has no statistical difference between them. The mean MU value of RapidArc and IMRT was 550 and 1379;The mean treatment time of RapidArc and IMRT was 165s and 447s .Compared to IMRT, the delivery time and the MU value of RapidArc were reduced by 63% and 60% respectively. Conclusions: For locally advanced NPC, both RapidArc and IMRT reached the clinic requirement. The target volume coverage was similar for the different techniques. The RapidArc technique showed some improvements in organs at risk and other tissue sparing while using reduced monitor units and delivery time. Author Disclosure: S. Yan: None.
2624
Three-Dimensional Conformal Radiation Therapy in the Salvage of 212 Locally Recurrent Nasopharyngeal Carcinoma Cases
S. F. Qiu1,2, J. D. J. Lu1, S. J. Lin3, I. W. K. Tham1, J. Lu4, J. J. Pan3 1 National University Cancer Institute Singapore, Singapore 119228, Singapore, 2Department of Radiation Oncology, Cancer Hospital of Fujian Medical University, Fuzhou, China, 3Department of Radiation Oncology, Cancer Hospital of Fujian Medical University, Fuzhou, China, 4of Radiation Oncology, Cancer Hospital of Fujian Medical University, Fuzhou, China
Purpose/Objective(s): Local recurrences of nasopharyngeal carcinoma (NPC) may be salvaged by re-irradiation using conventional techniques, but with significant morbidity. Three-dimensional conformal radiation therapy (3D-CRT) including intensity