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Surgery plus Postoperative Radiation Therapy for Thymic Epithelial Tumor
S496
I. J. Radiation Oncology
2449
● Biology ● Physics
Volume 63, Number 2, Supplement, 2005
Surgery plus Postoperative Radiation Therapy for Thymic Epithelial Tumor
1
D. Oh, Y. Ahn,1 Y. Park,1 H. Nam,1 S. Yoon,1 K. Kim,2 J. Kim,2 Y. Shim,2 J. Han3 Radiation Oncology, Samsung Medical Center, Sungkyunkwan University, School of Medicine, Seoul, South Korea, 2 Thoracic surgery, Samsung Medical Center, Sungkyunkwan University, School of Medicine, Seoul, South Korea, 3 Pathology, Samsung Medical Center, Sungkyunkwan University, School of Medicine, Seoul, South Korea 1
Purpose/Objective: This study was conducted to analyze prognostic significance of World Health Organization (WHO) thymic epithelial tumor (TET) subtype and to assess optimal radiation target volume in patients receiving surgery and adjuvant radiation therapy. Materials/Methods: The records of 160 TET patients, who received surgical resection at Samsung Medical Center, from Dec. 1994 till June 2004, were retrospectively reviewed. Postoperative radiation therapy (PORT) was delivered to 98 patients who had one or more of the risk factors, which included (1) the suspicion in the completeness of resection, (2) positive resection margin, (3) Masaoka stage II⬃IV, and (4) WHO type B2⬃C. Using 6 or 10 MV photons, a mean of 54.0 Gy by 1.8 or 2.0 Gy per fraction was focused to the volume confined to the primary tumor bed only that did not include the regional lymphatics nor pleuro-pericardial spaces electively. The prognostic factor and pattern of failure were analyzed. Results: Seven patients suffered from symptomatic radiation pneumonitis needing steroid medication, while only one did symptomatic radiation esophagitis. Recurrence was observed in 9 patients, none of which was within the PORT volume: pleuro-pericardial seeding in six; distant metastases in two; and mediastinal recurrence in one who were with WHO type C. Overall survival rate was 87.3% at 5 years. Age (more than 60 years 77.8%, less than 60 years 91.1%; p⫽0.03), Masaoka stage (I 92.2%, II 95.4%, III 82.1%, IV 67.5%; p⫽0.001), WHO type (A-B1 96.0%, B2-C 82.3%; p⫽0.001), and extent of resection (R0 resection 92.3%, R1 or R2 resection 72.6%; p⫽0.001) were the significant prognostic factors according to the univariate analyses. Only WHO type, however, proved to be significant according to the multivariate analyses. Conclusions: WHO type was confirmed as a very important prognostic factor with respect to survival. PORT confined to the primary tumor bed only is suggested to be optimal considering excellent in-field control and acceptable radiation-related morbidity. Development of effective systemic chemotherapy to reduce the pleuro-pericardial seeding may be warranted.
2450
The Dosimetric Impact of Respiration Motion on 3D, IMRT, and Tomotherapy Treatment Delivery
T. Byrne, C. Ramsey, S. Mahan, D. Chase Thompson Cancer Center, Knoxville, TN Purpose/Objective: The accuracy of delivered dose distributions in patients is sensitive to respiration motion during treatment delivery. First and foremost, motion during treatment delivery blurs the edges of the delivered dose distribution. For intensity modulated radiation therapy (IMRT), there is an additional error that arises from the interplay between the motion of the target and the motion of the multileaf collimator sequence. This error could potentially be larger in helical tomotherapy treatment delivery where the treatment is delivered slice-by-slice. The purpose of this work was to experimentally measure the impact of respiration motion for helical tomotherapy treatment delivery. Materials/Methods: Five lung cancer patients that were treated with helical tomotherapy were selected for this study. Treatments plans were created for 3D conformal, IMRT, and helical tomotherapy treatment delivery. All treatment plans used the same beam energy (6 MV), the same planning target volume (PTV), and a prescribed dose of 2 Gy per fraction to 90 percent of the PTV. A custom build motion phantom was used to simulate respiration motion. The motion phantom consisted of a motor driven platform that supported a homogenous 30 ⫻ 30 ⫻ 20 cm water equivalent phantom. The motion phantom has variable superior-inferior range of motion from 0.5 to 2.0-cm and period of 7 seconds. The dosimetric effects of respiration motion were evaluated by placing Kodak EDR2 film at 10-cm depth inside the motion phantom. The film was positioned in the coronal plane (parallel to the couch tabletop) and centered through the PTV. This measurement geometry was selected to measure the maximum respiration induced error. Composite dose distributions were obtained for treatment delivery with and without respiration motion for APPA, IMRT, and tomotherapy delivery. Each film was then scanned and analyzed for dosimetric differences using a commercially available film dosimetry system (Radiological Imaging Technologies, Inc., Colorado Springs, CO). Results: Dose difference statistics and profile statistic between the stationary and moving films showed the greatest motion error for IMRT delivery, and the least dose difference with AP/PA delivery. Tomotherapy delivery consistently fell between the two other delivery techniques. This trend was noted in dose tolerance levels 3%, 5%, 8%, and 10% throughout the study. Conclusions: Respiration motion can induce errors into any non-gated treatment delivery technique. If respiratory management techniques are not utilized, then the magnitude of this error should be measured as part of the patient specific IMRT quality assurance.
2451
Validation of Planned Surface and Build-Up Dose in Head and Neck Intensity Modulated Radiation Therapy
K.J. Hirmiz, J. Robar, M. Rajaraman, L. Mulroy, D. Wilke Radiation Oncology, Nova Scotia Cancer Centre, Dalhousie University, Halifax, NS, Canada Purpose/Objective: The accuracy of absorbed dose at the skin surface is crucial in head and neck IMRT, given the importance of either dose coverage of superficial nodal target volumes, or skin sparing, depending on the treatment geometry. However, accurate dose calculation in this region is difficult due to the complex mechanisms of surface dose, including electron
I. J. Radiation Oncology
2449
● Biology ● Physics
Volume 63, Number 2, Supplement, 2005
Surgery plus Postoperative Radiation Therapy for Thymic Epithelial Tumor
1
D. Oh, Y. Ahn,1 Y. Park,1 H. Nam,1 S. Yoon,1 K. Kim,2 J. Kim,2 Y. Shim,2 J. Han3 Radiation Oncology, Samsung Medical Center, Sungkyunkwan University, School of Medicine, Seoul, South Korea, 2 Thoracic surgery, Samsung Medical Center, Sungkyunkwan University, School of Medicine, Seoul, South Korea, 3 Pathology, Samsung Medical Center, Sungkyunkwan University, School of Medicine, Seoul, South Korea 1
Purpose/Objective: This study was conducted to analyze prognostic significance of World Health Organization (WHO) thymic epithelial tumor (TET) subtype and to assess optimal radiation target volume in patients receiving surgery and adjuvant radiation therapy. Materials/Methods: The records of 160 TET patients, who received surgical resection at Samsung Medical Center, from Dec. 1994 till June 2004, were retrospectively reviewed. Postoperative radiation therapy (PORT) was delivered to 98 patients who had one or more of the risk factors, which included (1) the suspicion in the completeness of resection, (2) positive resection margin, (3) Masaoka stage II⬃IV, and (4) WHO type B2⬃C. Using 6 or 10 MV photons, a mean of 54.0 Gy by 1.8 or 2.0 Gy per fraction was focused to the volume confined to the primary tumor bed only that did not include the regional lymphatics nor pleuro-pericardial spaces electively. The prognostic factor and pattern of failure were analyzed. Results: Seven patients suffered from symptomatic radiation pneumonitis needing steroid medication, while only one did symptomatic radiation esophagitis. Recurrence was observed in 9 patients, none of which was within the PORT volume: pleuro-pericardial seeding in six; distant metastases in two; and mediastinal recurrence in one who were with WHO type C. Overall survival rate was 87.3% at 5 years. Age (more than 60 years 77.8%, less than 60 years 91.1%; p⫽0.03), Masaoka stage (I 92.2%, II 95.4%, III 82.1%, IV 67.5%; p⫽0.001), WHO type (A-B1 96.0%, B2-C 82.3%; p⫽0.001), and extent of resection (R0 resection 92.3%, R1 or R2 resection 72.6%; p⫽0.001) were the significant prognostic factors according to the univariate analyses. Only WHO type, however, proved to be significant according to the multivariate analyses. Conclusions: WHO type was confirmed as a very important prognostic factor with respect to survival. PORT confined to the primary tumor bed only is suggested to be optimal considering excellent in-field control and acceptable radiation-related morbidity. Development of effective systemic chemotherapy to reduce the pleuro-pericardial seeding may be warranted.
2450
The Dosimetric Impact of Respiration Motion on 3D, IMRT, and Tomotherapy Treatment Delivery
T. Byrne, C. Ramsey, S. Mahan, D. Chase Thompson Cancer Center, Knoxville, TN Purpose/Objective: The accuracy of delivered dose distributions in patients is sensitive to respiration motion during treatment delivery. First and foremost, motion during treatment delivery blurs the edges of the delivered dose distribution. For intensity modulated radiation therapy (IMRT), there is an additional error that arises from the interplay between the motion of the target and the motion of the multileaf collimator sequence. This error could potentially be larger in helical tomotherapy treatment delivery where the treatment is delivered slice-by-slice. The purpose of this work was to experimentally measure the impact of respiration motion for helical tomotherapy treatment delivery. Materials/Methods: Five lung cancer patients that were treated with helical tomotherapy were selected for this study. Treatments plans were created for 3D conformal, IMRT, and helical tomotherapy treatment delivery. All treatment plans used the same beam energy (6 MV), the same planning target volume (PTV), and a prescribed dose of 2 Gy per fraction to 90 percent of the PTV. A custom build motion phantom was used to simulate respiration motion. The motion phantom consisted of a motor driven platform that supported a homogenous 30 ⫻ 30 ⫻ 20 cm water equivalent phantom. The motion phantom has variable superior-inferior range of motion from 0.5 to 2.0-cm and period of 7 seconds. The dosimetric effects of respiration motion were evaluated by placing Kodak EDR2 film at 10-cm depth inside the motion phantom. The film was positioned in the coronal plane (parallel to the couch tabletop) and centered through the PTV. This measurement geometry was selected to measure the maximum respiration induced error. Composite dose distributions were obtained for treatment delivery with and without respiration motion for APPA, IMRT, and tomotherapy delivery. Each film was then scanned and analyzed for dosimetric differences using a commercially available film dosimetry system (Radiological Imaging Technologies, Inc., Colorado Springs, CO). Results: Dose difference statistics and profile statistic between the stationary and moving films showed the greatest motion error for IMRT delivery, and the least dose difference with AP/PA delivery. Tomotherapy delivery consistently fell between the two other delivery techniques. This trend was noted in dose tolerance levels 3%, 5%, 8%, and 10% throughout the study. Conclusions: Respiration motion can induce errors into any non-gated treatment delivery technique. If respiratory management techniques are not utilized, then the magnitude of this error should be measured as part of the patient specific IMRT quality assurance.
2451
Validation of Planned Surface and Build-Up Dose in Head and Neck Intensity Modulated Radiation Therapy
K.J. Hirmiz, J. Robar, M. Rajaraman, L. Mulroy, D. Wilke Radiation Oncology, Nova Scotia Cancer Centre, Dalhousie University, Halifax, NS, Canada Purpose/Objective: The accuracy of absorbed dose at the skin surface is crucial in head and neck IMRT, given the importance of either dose coverage of superficial nodal target volumes, or skin sparing, depending on the treatment geometry. However, accurate dose calculation in this region is difficult due to the complex mechanisms of surface dose, including electron