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Radiation Re-treatment of the Spine Using CyberKnife Radiosurgery
Proceedings of the 47th Annual ASTRO Meeting
head. More recently wide bore (85 cm) CT scanners permit planning in both treatment positions. To determine whether arm position affects dosimetry and the relationship of target nodal groups to anatomic landmarks traditionally used for planning axillary node radiation treatment fields. Materials/Methods: Fourteen patients were scanned in a wide-bore CT in both the historic position with the ipsilateral arm held at 90 degrees by an arm board and in the narrow bore CT treatment planning position with both arms resting above the head in a custom vacuum-lock mold. Level I, II, III nodes were contoured on both CT’s for each patient. Target depths and relationship to the coracoid process were measured for each nodal group and optimized dose distributions were compared. In addition, four patients had clips placed at the top of their Level I and II node dissections and the position of these clips relative to anatomic landmarks was compared in each position. Results: The average difference between the historic and narrow bore CT positions in target depth was 8.5 mm (range ⫺4.7 mm to 24.9 mm) for level II nodes and 7.5 mm (range ⫺2.2mm to 27.4 mm) for level III nodes. The depth of nodes relative to skin surface was usually greater in the CT position with arms above the head. The average distance from the lateral border of the coracoid process to the lateral anatomic boundary of level II nodes was 11.8 mm (range 1.6 mm to 20.2 mm) in the historic position and 8.1 mm (range of ⫺4.7 mm to 25.7 mm) in the CT position. It was noted that standard historic posterior axillary boost fields that included only a small margin of lung tissue frequently excluded some Level II and III nodes. In plans optimized for adequate coverage of Level II and III, the mean dose for the deltopectoral nodal group, to which lymphatics of the arm drain, received 116.4% of the prescribed dose in the historical position and 112.4% in the narrow-bore CT position. Conclusions: Changes in arm position result in changes in the relationship between target nodes and anatomic landmarks used historically in treatment planning for breast cancer patients. Such changes could significantly impact the dose distribution unless treatment planning was based on 3D nodal contours. Clips placed at the top of Level I and II dissections are frequently lateral to the coracoid process in both treatment planning positions indicating that historical fields based on anatomic landmarks may well have underdosed or missed high level II and III nodes. The results of historical trials of postmastectomy radiation therapy may need reinterpretation as 3D treatment planning sheds light on the adequacy of historical treatment techniques.
2355
Radiation Re-treatment of the Spine Using CyberKnife Radiosurgery
G.J. Gagnon,1 F.C. Henderson,2,1 J. Liau,1 E. Balfour,1 B.T. Collins,1 K.W. Harter,1 D. McRae1 Radiation Medicine, Georgetown University Hospital, Washington, DC, 2Neurosurgery, Georgetown University Hospital, Washington, DC
1
Purpose/Objective: Although primary tumors of the spine are uncommon, metastatic involvement is a common occurrence. Morbidity associated with spinal involvement can leave these patients with functional limitations, pain, and poor quality of life. Because of the necessity of preserving the integrity of the spinal column and the proximal critical structures, treatments are limited. As a consequence, local recurrences, either symptomatic, clinical, or radiographic are all too common. When the primary mode of treatment has been radiotherapy, tumor recurrence creates a therapeutic dilemma, as further treatment carries a high complication risk. We have been treating patients who have failed prior radiotherapy with fractionated CyberKnife radiosurgery as retreatment. We feel that this technology is of considerable interest because of its precision, conformity, homogeneity, and ease of fractionation. Materials/Methods: 108 patients who had received prior external beam radiation to the spine were included if there was evidence of recurrent or progressive spinal disease. 700 cGy ⫻ 3 fractions (2100 cGy total) was given to a peripheral isodose contour. Outcome measures included follow-up neurological exams and MRI’s at 2, 6, 12, 18, and 24 months, pain assessment by the Visual Analog Scale (VAS), and quality of life measurement by the SF-12 Short Form Survey. Results: Acceptable treatment plans were designed on all patients, with the goal of limiting spinal cord dose to 900 cGy total to a small volume. Mean Conformality Index was 1.35 and mean Homogeneity Index was 1.30. Median survival was 15 months for the entire group. Pain scores were significantly decreased and this decrease was evident within 2 months. Duration of pain relief was prolonged, with a minority reporting recurrence of pain in the treated region during the duration of this study (see accompanying figure). Significant quality of life improvements were also seen by the SF-12 scores for both physical and mental domains. No complications have been observed. Conclusions: Stereotactic radiosurgery with the CyberKnife has been an effective treatment capable of delivering high-dose radiation to recurrent spinal tumors. Follow-up data including pain assessments and quality of life surveys appear quite favorable, considering the poor prognoses of these patients. This modality appears ideally suited for retreatment of these spinal lesions.
Duration of pain relief after CyberKnife radiosurgery as re-treatment of symptomatic spinal malignancy.
S439
head. More recently wide bore (85 cm) CT scanners permit planning in both treatment positions. To determine whether arm position affects dosimetry and the relationship of target nodal groups to anatomic landmarks traditionally used for planning axillary node radiation treatment fields. Materials/Methods: Fourteen patients were scanned in a wide-bore CT in both the historic position with the ipsilateral arm held at 90 degrees by an arm board and in the narrow bore CT treatment planning position with both arms resting above the head in a custom vacuum-lock mold. Level I, II, III nodes were contoured on both CT’s for each patient. Target depths and relationship to the coracoid process were measured for each nodal group and optimized dose distributions were compared. In addition, four patients had clips placed at the top of their Level I and II node dissections and the position of these clips relative to anatomic landmarks was compared in each position. Results: The average difference between the historic and narrow bore CT positions in target depth was 8.5 mm (range ⫺4.7 mm to 24.9 mm) for level II nodes and 7.5 mm (range ⫺2.2mm to 27.4 mm) for level III nodes. The depth of nodes relative to skin surface was usually greater in the CT position with arms above the head. The average distance from the lateral border of the coracoid process to the lateral anatomic boundary of level II nodes was 11.8 mm (range 1.6 mm to 20.2 mm) in the historic position and 8.1 mm (range of ⫺4.7 mm to 25.7 mm) in the CT position. It was noted that standard historic posterior axillary boost fields that included only a small margin of lung tissue frequently excluded some Level II and III nodes. In plans optimized for adequate coverage of Level II and III, the mean dose for the deltopectoral nodal group, to which lymphatics of the arm drain, received 116.4% of the prescribed dose in the historical position and 112.4% in the narrow-bore CT position. Conclusions: Changes in arm position result in changes in the relationship between target nodes and anatomic landmarks used historically in treatment planning for breast cancer patients. Such changes could significantly impact the dose distribution unless treatment planning was based on 3D nodal contours. Clips placed at the top of Level I and II dissections are frequently lateral to the coracoid process in both treatment planning positions indicating that historical fields based on anatomic landmarks may well have underdosed or missed high level II and III nodes. The results of historical trials of postmastectomy radiation therapy may need reinterpretation as 3D treatment planning sheds light on the adequacy of historical treatment techniques.
2355
Radiation Re-treatment of the Spine Using CyberKnife Radiosurgery
G.J. Gagnon,1 F.C. Henderson,2,1 J. Liau,1 E. Balfour,1 B.T. Collins,1 K.W. Harter,1 D. McRae1 Radiation Medicine, Georgetown University Hospital, Washington, DC, 2Neurosurgery, Georgetown University Hospital, Washington, DC
1
Purpose/Objective: Although primary tumors of the spine are uncommon, metastatic involvement is a common occurrence. Morbidity associated with spinal involvement can leave these patients with functional limitations, pain, and poor quality of life. Because of the necessity of preserving the integrity of the spinal column and the proximal critical structures, treatments are limited. As a consequence, local recurrences, either symptomatic, clinical, or radiographic are all too common. When the primary mode of treatment has been radiotherapy, tumor recurrence creates a therapeutic dilemma, as further treatment carries a high complication risk. We have been treating patients who have failed prior radiotherapy with fractionated CyberKnife radiosurgery as retreatment. We feel that this technology is of considerable interest because of its precision, conformity, homogeneity, and ease of fractionation. Materials/Methods: 108 patients who had received prior external beam radiation to the spine were included if there was evidence of recurrent or progressive spinal disease. 700 cGy ⫻ 3 fractions (2100 cGy total) was given to a peripheral isodose contour. Outcome measures included follow-up neurological exams and MRI’s at 2, 6, 12, 18, and 24 months, pain assessment by the Visual Analog Scale (VAS), and quality of life measurement by the SF-12 Short Form Survey. Results: Acceptable treatment plans were designed on all patients, with the goal of limiting spinal cord dose to 900 cGy total to a small volume. Mean Conformality Index was 1.35 and mean Homogeneity Index was 1.30. Median survival was 15 months for the entire group. Pain scores were significantly decreased and this decrease was evident within 2 months. Duration of pain relief was prolonged, with a minority reporting recurrence of pain in the treated region during the duration of this study (see accompanying figure). Significant quality of life improvements were also seen by the SF-12 scores for both physical and mental domains. No complications have been observed. Conclusions: Stereotactic radiosurgery with the CyberKnife has been an effective treatment capable of delivering high-dose radiation to recurrent spinal tumors. Follow-up data including pain assessments and quality of life surveys appear quite favorable, considering the poor prognoses of these patients. This modality appears ideally suited for retreatment of these spinal lesions.
Duration of pain relief after CyberKnife radiosurgery as re-treatment of symptomatic spinal malignancy.
S439