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The evaluation of the 3D treatment planning in stereotactic hypofractionated single high dose radiotherapy for lung tumor
Proceedings of the 43rd Annual ASTRO Meeting
significant predictor of brain metastasis. However, there is evidence from the survival analysis that high Ki-67 expression does predict lower disease free survival. Low p53 expression predicted poor prognosis, affecting overall survival and non-brain DM failure. However, bcl-2 expression was difficult to interpret because of negative staining for the majority of patients in this study. SCC cases had high Ki-67 and p53 expression, whereas AC cases had low Ki-67 and p53 expression. Additional biomarker staining and multivariate analysis of biomarkers to predict brain metastasis among patients with NSCLC is underway.
2249
The Evaluation of the 3D Treatment Planning in Stereotactic Hypofractionated Single High Dose Radiotherapy for Lung Tumor
Y. Negoro, Y. Nagata, T. Mizowaki, M. Kokubo, T. Aoki, N. Araki, M. Mitsumori, Y. Shibamoto, M. Hiraoka Therapeutic Radiation and Oncology, Kyoto University, Kyoto city, Japan Purpose: In July 1998, we started administrating the stereotactic hypofractionated single high dose radiotherapy for solitary lung tumor using a stereotactic body frame. The treatment planning was performed using the non-coplanar multiple static fields. When using the method, the range of the couch angle and the gantry angle of the linear accelerator was limitted in order to avoid a collision between the couch and the gantry. The purpose of this study was to analyze the DVH of the CTV and OARs in treatment planning of the non-coplanar multiple static fields using a body frame. Materials and Methods: Treatment planning and dose distributions were analyzed in 41 patients with a solitary lung tumor who and underwent stereotactic radiotherapy between July 1998 and November 2000. The 3D treatment plannings were made with a 3D RTP ( radiation treatment planning ) machine - CADPLAN (Varian) - using the non-coplanar multiple static port method. In regard to the patient immobilization, the stereotactic body frame (ELEKTA) was used for tratment planning and treatment delivery in all these cases. A total dose of 48 Gy in 4 fractions at the isocenter of the beam was delivered with 6MV X-ray over 5 to 13 (median : 12) days. Treatment planning was established to maintain the target dose homogeneity within 15%, and to decrease the lung volume irradiated over 20 Gy to less than 25%. To avoid collision between the couch and the gantry of the linear accelerator, 3 or 4 ports were selected as coplanar - that is the couch angle of the ports were 0 - and the remaining 3 or 4 ports were selected to be non-coplanar with a couch angle between -40 deg. and 40 deg. The port in which the spinal cord would be directly irradiated was avoided in this study. The number of ports selected was between 5 and 10. Results: The volume of the CTV ranged from 0.3 to 37.9 cc (mean : 12cc). The number of ports used in each case ranged from 5 to 10 (median : 6). The gantry angle was between -60 deg. and 60 deg. in 69% of non-coplanar ports, while it was 54% of all ports used. The couch angle was described above. The maximum and minimum dose to the target was between 100% and 108% of the isocenter dose , and was between 78% and 99%, respectively. The lung volume irradiated with more than 20 Gy ranged from 0.3% to 11.6% (mean : 4.3%) of the whole lung volume. The maximum dose to the spinal cord ranged from 0.3 to 2.0 Gy per fraction (mean : 0.68Gy). The maximum dose of the ipsilateral main bronchus was greater than 6 Gy in 3 cases. However, its volume was less than 1.5cc. The maximum dose of the ipsilateral pulmonary artery trunk was greater than 10 Gy in 6 cases, in which the volume over 10 Gy was less than 2 cc. There were no significant complications such as cough, fever, hemosputa or symptomatic radiation pneumonitis observed clinically to date. Conclusion: Using the non-coplanar multiple static port method, homogenous target dose distribution avoiding high dose to normal tissue could be obtained. The planning method was acceptable. Further studies are being designed using dynamic arc conformal therapy, and a simpler algorithm to optimize treatment planning is being developed.
2250
Radiotherapy for Lung Cancer: Can IMRT Decrease the Risk of Esophagitis
1
P. Giraud , K.E. Rosenzweig1, E. Yorke2, J. Yahalom1, N. Fournier-Bidoz2, S. Spirou2, G. Mageras2, H. Amols2, S.A. Leibel1 1 Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY, 2Medical Physics, Memorial SloanKettering Cancer Center, New York, NY Purpose: Esophagitis is a main dose limiting toxicity of radiation therapy for lung cancer. Studies have shown esophagitis rates as high as 50% when concomitant chemotherapy and radiation therapy are used. Currently there is no way to avoid irradiating the esophagus during thoracic radiation. This study evaluates the potential of intensity modulated radiation therapy (IMRT) to spare the esophagus in lung radiotherapy. Materials and Methods: To confidently protect the esophagus, its change in location due to day-to day variation and respiration was quantified. Thirteen patients underwent two thoracic CT scans about one week apart in the same treatment position with arms raised. The esophagus was contoured on each CT scan. Fixed bony anatomy was used to register the two CT sets. Day-to-day variations between these two CT sets were quantified by calculating the shift in the position of the center of mass of the esophagus. Six patients underwent breath-synchronized CT scanning, using a commercial respiratory gating system (Varian Medical Inc). An end-inspiration and an end-expiration CT scan were performed in the same supine-arms-up position as in the previous study. The change in the location of the esophagus was quantified by the same methodology as previously described. To evaluate esophagus sparing by inverse-planned sliding window IMRT vs three-dimensional conformal radiation therapy (3D-CRT), plans were generated for ten non-small cell lung cancer patients with different tumor locations. Maximum allowed cord and esophagus doses were 45Gy and 80Gy respectively. We also required 75% of the lung to be below 25Gy and 50% of the esophagus to be below 32Gy. Beam directions and prescription doses were the same for IMRT and 3D-CRT. Results: The mean day-to-day change in the position of the center of mass was 2, 1.5 and 7.8mm in the lateral (LAT), anterior-posterior (AP) and superior-inferior (SI) directions, respectively. Breathing caused mean center of mass shifts of 2.6, 2.8 and 11.5mm in the LAT, AP and SI directions, respectively. Based on these measurements, and the systematic errors measured in a separate study, the total margins added in AP and LAT directions to the cervical, mid and lower esophagus were 5, 6 and 5mm, respectively, so that there was an 85% probability that the entire esophagus would lie within the margin.
355
significant predictor of brain metastasis. However, there is evidence from the survival analysis that high Ki-67 expression does predict lower disease free survival. Low p53 expression predicted poor prognosis, affecting overall survival and non-brain DM failure. However, bcl-2 expression was difficult to interpret because of negative staining for the majority of patients in this study. SCC cases had high Ki-67 and p53 expression, whereas AC cases had low Ki-67 and p53 expression. Additional biomarker staining and multivariate analysis of biomarkers to predict brain metastasis among patients with NSCLC is underway.
2249
The Evaluation of the 3D Treatment Planning in Stereotactic Hypofractionated Single High Dose Radiotherapy for Lung Tumor
Y. Negoro, Y. Nagata, T. Mizowaki, M. Kokubo, T. Aoki, N. Araki, M. Mitsumori, Y. Shibamoto, M. Hiraoka Therapeutic Radiation and Oncology, Kyoto University, Kyoto city, Japan Purpose: In July 1998, we started administrating the stereotactic hypofractionated single high dose radiotherapy for solitary lung tumor using a stereotactic body frame. The treatment planning was performed using the non-coplanar multiple static fields. When using the method, the range of the couch angle and the gantry angle of the linear accelerator was limitted in order to avoid a collision between the couch and the gantry. The purpose of this study was to analyze the DVH of the CTV and OARs in treatment planning of the non-coplanar multiple static fields using a body frame. Materials and Methods: Treatment planning and dose distributions were analyzed in 41 patients with a solitary lung tumor who and underwent stereotactic radiotherapy between July 1998 and November 2000. The 3D treatment plannings were made with a 3D RTP ( radiation treatment planning ) machine - CADPLAN (Varian) - using the non-coplanar multiple static port method. In regard to the patient immobilization, the stereotactic body frame (ELEKTA) was used for tratment planning and treatment delivery in all these cases. A total dose of 48 Gy in 4 fractions at the isocenter of the beam was delivered with 6MV X-ray over 5 to 13 (median : 12) days. Treatment planning was established to maintain the target dose homogeneity within 15%, and to decrease the lung volume irradiated over 20 Gy to less than 25%. To avoid collision between the couch and the gantry of the linear accelerator, 3 or 4 ports were selected as coplanar - that is the couch angle of the ports were 0 - and the remaining 3 or 4 ports were selected to be non-coplanar with a couch angle between -40 deg. and 40 deg. The port in which the spinal cord would be directly irradiated was avoided in this study. The number of ports selected was between 5 and 10. Results: The volume of the CTV ranged from 0.3 to 37.9 cc (mean : 12cc). The number of ports used in each case ranged from 5 to 10 (median : 6). The gantry angle was between -60 deg. and 60 deg. in 69% of non-coplanar ports, while it was 54% of all ports used. The couch angle was described above. The maximum and minimum dose to the target was between 100% and 108% of the isocenter dose , and was between 78% and 99%, respectively. The lung volume irradiated with more than 20 Gy ranged from 0.3% to 11.6% (mean : 4.3%) of the whole lung volume. The maximum dose to the spinal cord ranged from 0.3 to 2.0 Gy per fraction (mean : 0.68Gy). The maximum dose of the ipsilateral main bronchus was greater than 6 Gy in 3 cases. However, its volume was less than 1.5cc. The maximum dose of the ipsilateral pulmonary artery trunk was greater than 10 Gy in 6 cases, in which the volume over 10 Gy was less than 2 cc. There were no significant complications such as cough, fever, hemosputa or symptomatic radiation pneumonitis observed clinically to date. Conclusion: Using the non-coplanar multiple static port method, homogenous target dose distribution avoiding high dose to normal tissue could be obtained. The planning method was acceptable. Further studies are being designed using dynamic arc conformal therapy, and a simpler algorithm to optimize treatment planning is being developed.
2250
Radiotherapy for Lung Cancer: Can IMRT Decrease the Risk of Esophagitis
1
P. Giraud , K.E. Rosenzweig1, E. Yorke2, J. Yahalom1, N. Fournier-Bidoz2, S. Spirou2, G. Mageras2, H. Amols2, S.A. Leibel1 1 Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY, 2Medical Physics, Memorial SloanKettering Cancer Center, New York, NY Purpose: Esophagitis is a main dose limiting toxicity of radiation therapy for lung cancer. Studies have shown esophagitis rates as high as 50% when concomitant chemotherapy and radiation therapy are used. Currently there is no way to avoid irradiating the esophagus during thoracic radiation. This study evaluates the potential of intensity modulated radiation therapy (IMRT) to spare the esophagus in lung radiotherapy. Materials and Methods: To confidently protect the esophagus, its change in location due to day-to day variation and respiration was quantified. Thirteen patients underwent two thoracic CT scans about one week apart in the same treatment position with arms raised. The esophagus was contoured on each CT scan. Fixed bony anatomy was used to register the two CT sets. Day-to-day variations between these two CT sets were quantified by calculating the shift in the position of the center of mass of the esophagus. Six patients underwent breath-synchronized CT scanning, using a commercial respiratory gating system (Varian Medical Inc). An end-inspiration and an end-expiration CT scan were performed in the same supine-arms-up position as in the previous study. The change in the location of the esophagus was quantified by the same methodology as previously described. To evaluate esophagus sparing by inverse-planned sliding window IMRT vs three-dimensional conformal radiation therapy (3D-CRT), plans were generated for ten non-small cell lung cancer patients with different tumor locations. Maximum allowed cord and esophagus doses were 45Gy and 80Gy respectively. We also required 75% of the lung to be below 25Gy and 50% of the esophagus to be below 32Gy. Beam directions and prescription doses were the same for IMRT and 3D-CRT. Results: The mean day-to-day change in the position of the center of mass was 2, 1.5 and 7.8mm in the lateral (LAT), anterior-posterior (AP) and superior-inferior (SI) directions, respectively. Breathing caused mean center of mass shifts of 2.6, 2.8 and 11.5mm in the LAT, AP and SI directions, respectively. Based on these measurements, and the systematic errors measured in a separate study, the total margins added in AP and LAT directions to the cervical, mid and lower esophagus were 5, 6 and 5mm, respectively, so that there was an 85% probability that the entire esophagus would lie within the margin.
355