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Comparison of Dose Escalation to Lung Tumors via IMRT Approaches to Conventional Treatment Plans with or without Prophylactic Nodal Irradiation
S508
I. J. Radiation Oncology
2467
● Biology ● Physics
Volume 63, Number 2, Supplement, 2005
Comparison of Dose Escalation to Lung Tumors via IMRT Approaches to Conventional Treatment Plans with or without Prophylactic Nodal Irradiation
J.M. Varlotto,1 J.C. Flickinger,2 E. Holupka,1 S. Berman,1 G. Cryan1 1
Radiation Oncology, Beth Israel Deaconess Medical Center, Boston, MA, 2Radiation Oncology, University of Pittsburgh Cancer Institute, Pittsburgh, PA Purpose/Objective: 1.To determine whether two different IMRT approaches delivered to a dose of 70Gy⫹ can be given with similar normal tissue toxicity as per conventional radiotherapy treatments with or without prophylactic nodal irradiation. 2. To determine the difference in monitor units, tumor and normal tissue doses when the best IMRT technique is calculated with and without lung heterogeneity corrections. Materials/Methods: Ten randomly selected CT Scans from lung cancer patients were chosen for testing. Conventional treatment plans included enlarged lymph nodes and tumor volumes with (CPNI) or without (CNO) prophylactic treatment of hilar and mediastinal lymph nodes. Patients were treated with AP/PA fields to 40Gy and then received off-cord oblique fields to 60Gy. IMRT plans were created with either five equally-spaced axial fields(A-IMRT) or a six-field approach using non-axial fields(NA-IMRT). The NA-IMRT Plans were then run using the same dose constraints with lung heterogeneity corrections (NA-IMRT-H). The IMRT plans were set to administer 70Gy⫹ to the CTV using the following idealized dose constraints: ⬍30% of the lung volume exceeding 20Gy (V20 ⬍30%), ⬍28% of the esophagus receiving 55Gy (V55 ⬍28%), ⬍20% of the heart receiving 40Gy (V40 ⬍ 20%), and a maximum spinal cord dose of 40Gy. However, constraints for the IMRT plans were often relaxed depending upon tumor volume and location. IMRT plans were aborted when a CTV dose of 70Gy could not be given without exceeding one of the following dose constraints: esophageal V62Gy ⬎ 30%, cardiac V40Gy ⬎50%, pulmonary 20Gy ⬎40%, and a maximum spinal cord dose exceeding 50Gy. Results: Median CTV Volume was noted to be 205.33cc(88.48 – 469.21). Although all NA-IMRT plans were able to be completed, five A-IMRT plans could not be completed. The completed A-IMRT plans had significantly smaller mean CTVs (122.78cc) than the incomplete plans(312.14cc). Comparing the completed A-IMRT plans to the NA-IMRT plans, the A-IMRT plans had a significantly higher mean esophageal V55 (29.83% vs. 28.34%), mean pulmonary V20(38.01% vs. 30.07%) and mean heart doses (25.64Gy vs. 22.23Gy). Mean and minimum CTV doses using NA-IMRT were 75.27Gy and 70.28Gy and were demonstrated to be significantly higher than the three other techniques. However, the increased tumor dose came at the expense of a significantly higher mean heart dose (22.23Gy) as compared to CNO(17.05Gy) and significantly higher mean esophageal, lung doses (32.03Gy,25.38Gy) than both the CNO (17.21Gy, 12.05Gy)and CPNI(28.46Gy, 21.33Gy) approaches. Similarly, the mean pulmonary V20 and the mean esophageal V55 were significantly higher with the NA-IMRT treatments as compared to CNO and CPNI techniques. The difference in the MU, minimal and mean tumor doses between NA-IMRT and NA-IMRT-H were not significantly different with values of 443.0 and 453.3, 70.28Gy and 71.67Gy, and 75.27Gy and 75.77Gy, respectively. Interestingly, all mean normal tissue doses were significantly lower with NA-IMRT-H as compared to the NA-IMRT plans including mean heart doses (18.04Gy and 22.23Gy), mean esophageal doses (30.63Gy and 32.03Gy), and mean lung doses (17.14Gy and 25.38Gy). Conclusions: The NA-IMRT approach was more feasible compared to the A-IMRT technique, especially in larger tumor volumes. Although NA-IMRT yielded significantly higher mean and median tumor doses than all other techniques, almost all normal tissue doses were significantly higher as compared to the conventional plans. By using lung heterogeneity corrections with the NA-IMRT technique, equivalent tumor doses and monitor units were maintained while normal tissues doses were significantly reduced.
2468
Image Guided Radiotherapy Plan Evaluation based on Deformable Dose Registration from Daily On-line Positioning Images
G. Olivera,1,3 W. Lu,1 K. Ruchala,1 Q. Chen,1 K. Langen,2 S. Meeks,2 P. Kupelian3 1
Tomotherapy Inc, Madison, WI, 2Radiation Oncology, M. D. Anderson Cancer Center Orlando, Orlando, FL, 3Medical Physics, University of Wisconsin, Madison, WI
Purpose/Objective: Apply a fast deformable registration (DR) technique to accumulate radiation dose and quantitatively evaluate treatment results. Generate daily contours automatically using deformation maps and the original planning structures set as a template. Evaluate daily volumes changes using automatic techniques. Materials/Methods: We retrospectively studied different anatomical sites using the daily TomoTherapy MVCT generated for daily patient positioning. These data sets include 3 lung cases, 5 head-neck cases, 3 prostate cases and 2 pelvis cases. Each case has one KVCT image and typically 30 – 40 MVCT images. We registered the MVCT images with the corresponding planning KVCT. Based on the DR, the daily delivered doses are registered to the reference frame and accumulated. The planning DVH and the accumulated delivery DVH are compared. The daily structures are automatically re-contoured using deformation maps for each daily MVCT. Results: When analyzing the DVHs for the head and neck cases it is typical to find different target hot and cold spots if deformable dose evaluation is used. For cases such as prostate, where the anatomy changes can be significant for the sensitive structures such as rectum or bladder, the DVH results can change very noticeable if DR is used to accumulate dose.
I. J. Radiation Oncology
2467
● Biology ● Physics
Volume 63, Number 2, Supplement, 2005
Comparison of Dose Escalation to Lung Tumors via IMRT Approaches to Conventional Treatment Plans with or without Prophylactic Nodal Irradiation
J.M. Varlotto,1 J.C. Flickinger,2 E. Holupka,1 S. Berman,1 G. Cryan1 1
Radiation Oncology, Beth Israel Deaconess Medical Center, Boston, MA, 2Radiation Oncology, University of Pittsburgh Cancer Institute, Pittsburgh, PA Purpose/Objective: 1.To determine whether two different IMRT approaches delivered to a dose of 70Gy⫹ can be given with similar normal tissue toxicity as per conventional radiotherapy treatments with or without prophylactic nodal irradiation. 2. To determine the difference in monitor units, tumor and normal tissue doses when the best IMRT technique is calculated with and without lung heterogeneity corrections. Materials/Methods: Ten randomly selected CT Scans from lung cancer patients were chosen for testing. Conventional treatment plans included enlarged lymph nodes and tumor volumes with (CPNI) or without (CNO) prophylactic treatment of hilar and mediastinal lymph nodes. Patients were treated with AP/PA fields to 40Gy and then received off-cord oblique fields to 60Gy. IMRT plans were created with either five equally-spaced axial fields(A-IMRT) or a six-field approach using non-axial fields(NA-IMRT). The NA-IMRT Plans were then run using the same dose constraints with lung heterogeneity corrections (NA-IMRT-H). The IMRT plans were set to administer 70Gy⫹ to the CTV using the following idealized dose constraints: ⬍30% of the lung volume exceeding 20Gy (V20 ⬍30%), ⬍28% of the esophagus receiving 55Gy (V55 ⬍28%), ⬍20% of the heart receiving 40Gy (V40 ⬍ 20%), and a maximum spinal cord dose of 40Gy. However, constraints for the IMRT plans were often relaxed depending upon tumor volume and location. IMRT plans were aborted when a CTV dose of 70Gy could not be given without exceeding one of the following dose constraints: esophageal V62Gy ⬎ 30%, cardiac V40Gy ⬎50%, pulmonary 20Gy ⬎40%, and a maximum spinal cord dose exceeding 50Gy. Results: Median CTV Volume was noted to be 205.33cc(88.48 – 469.21). Although all NA-IMRT plans were able to be completed, five A-IMRT plans could not be completed. The completed A-IMRT plans had significantly smaller mean CTVs (122.78cc) than the incomplete plans(312.14cc). Comparing the completed A-IMRT plans to the NA-IMRT plans, the A-IMRT plans had a significantly higher mean esophageal V55 (29.83% vs. 28.34%), mean pulmonary V20(38.01% vs. 30.07%) and mean heart doses (25.64Gy vs. 22.23Gy). Mean and minimum CTV doses using NA-IMRT were 75.27Gy and 70.28Gy and were demonstrated to be significantly higher than the three other techniques. However, the increased tumor dose came at the expense of a significantly higher mean heart dose (22.23Gy) as compared to CNO(17.05Gy) and significantly higher mean esophageal, lung doses (32.03Gy,25.38Gy) than both the CNO (17.21Gy, 12.05Gy)and CPNI(28.46Gy, 21.33Gy) approaches. Similarly, the mean pulmonary V20 and the mean esophageal V55 were significantly higher with the NA-IMRT treatments as compared to CNO and CPNI techniques. The difference in the MU, minimal and mean tumor doses between NA-IMRT and NA-IMRT-H were not significantly different with values of 443.0 and 453.3, 70.28Gy and 71.67Gy, and 75.27Gy and 75.77Gy, respectively. Interestingly, all mean normal tissue doses were significantly lower with NA-IMRT-H as compared to the NA-IMRT plans including mean heart doses (18.04Gy and 22.23Gy), mean esophageal doses (30.63Gy and 32.03Gy), and mean lung doses (17.14Gy and 25.38Gy). Conclusions: The NA-IMRT approach was more feasible compared to the A-IMRT technique, especially in larger tumor volumes. Although NA-IMRT yielded significantly higher mean and median tumor doses than all other techniques, almost all normal tissue doses were significantly higher as compared to the conventional plans. By using lung heterogeneity corrections with the NA-IMRT technique, equivalent tumor doses and monitor units were maintained while normal tissues doses were significantly reduced.
2468
Image Guided Radiotherapy Plan Evaluation based on Deformable Dose Registration from Daily On-line Positioning Images
G. Olivera,1,3 W. Lu,1 K. Ruchala,1 Q. Chen,1 K. Langen,2 S. Meeks,2 P. Kupelian3 1
Tomotherapy Inc, Madison, WI, 2Radiation Oncology, M. D. Anderson Cancer Center Orlando, Orlando, FL, 3Medical Physics, University of Wisconsin, Madison, WI
Purpose/Objective: Apply a fast deformable registration (DR) technique to accumulate radiation dose and quantitatively evaluate treatment results. Generate daily contours automatically using deformation maps and the original planning structures set as a template. Evaluate daily volumes changes using automatic techniques. Materials/Methods: We retrospectively studied different anatomical sites using the daily TomoTherapy MVCT generated for daily patient positioning. These data sets include 3 lung cases, 5 head-neck cases, 3 prostate cases and 2 pelvis cases. Each case has one KVCT image and typically 30 – 40 MVCT images. We registered the MVCT images with the corresponding planning KVCT. Based on the DR, the daily delivered doses are registered to the reference frame and accumulated. The planning DVH and the accumulated delivery DVH are compared. The daily structures are automatically re-contoured using deformation maps for each daily MVCT. Results: When analyzing the DVHs for the head and neck cases it is typical to find different target hot and cold spots if deformable dose evaluation is used. For cases such as prostate, where the anatomy changes can be significant for the sensitive structures such as rectum or bladder, the DVH results can change very noticeable if DR is used to accumulate dose.