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Quantitative Assessment of Lung Function in Stage I and Stage III Lung Radiation Therapy Patients Using 4DCT-based Ventilation Imaging
S754
International Journal of Radiation Oncology Biology Physics
3425
cancer patients, calculating ventilation maps from 4DCTs provides spatial lung function information at no extra dosimetric cost to the patient. Studies are underway to validate 4DCT-based ventilation and to use existing 4DCT data to study lung function and optimize treatment plans based on ventilation. The purpose of the current study was to use 4DCT-based ventilation imaging to quantitatively compare lung function between stage I and stage III lung cancer patients. Materials/Methods: Twenty-eight stage I lung cancer patients and 69 stage III lung cancer patients were analyzed. Stage I patients were treated using SBRT and the stage III group were treated using IMRT or 3D-CRT. Each patient had a pre-treatment 4DCT simulation performed as part of treatment planning. The 4DCT data were used to calculate pre-treatment ventilation maps. For each case, a deformable image registration algorithm was used to link corresponding lung volume elements between the inhale and exhale phase of the 4DCT dataset. Following spatial registration, corresponding Hounsfield Units were input into a density-change-based model for quantifying the local ventilation. For each patient, the visually observed ventilation defects were evaluated, the ipsilateral to contralateral ventilation ratio was calculated, and the standard deviation of the ventilation throughout the entire lung was computed. Ventilation metrics were compared between the stage I and stage III groups. Results: Out of 69 stage III patients, 24 (34%) had a visually observed ventilation defect, while 6 (21%) stage I patients had an observed defect. The ipsilateral to contralateral ventilation ratio was 0.97 0.09 for stage I patients, indicating evenly distributed lung function. For stage III patients, the ratio was 0.83 0.05 indicating compromised lung function in the ipsilateral lung. The differences between the groups approached statistical significance (p Z 0.11). The average standard deviation was 0.19 and 0.16 for stage III and stage I patients respectively. The results approached statistical significance (p Z 0.135). Conclusions: Our study uses a new form of ventilation imaging to quantitatively compare lung function between stage I and stage III lung cancer patients. Our data showed differences in lung function between stage I and stage III lung cancer patients. Better understanding of the normal lung function in patients prior to receiving IMRT or SBRT may provide opportunities to lessen the risk of radiation toxicity and assist in personalizing treatment plans in cases where the patient’s baseline lung function is compromised. Author Disclosure: Y. Vinogradskiy: None. G. Gan: None. R. Castillo: None. E. Castillo: None. M. Martel: None. T. Guerrero: None. M. Miften: None.
Analysis of Radiation-induced Toxicity in Patients Receiving Stereotactic Body Radiation Therapy (SBRT) for Lung Tumors J. Chang,1 B. Wen,2 P. Singh,1 R. Bassalow,1 B. Parashar,1 A.M. Sabbas,1 G.A. Wernicke,1 and K.C. Chao1; 1New York Presbyterian - Weill Cornell Medical College, New York, NY, 2Sun Yat-Sen University First Affiliated Hospital, Guangzhou, China Purpose/Objective(s): To analyze and model the treatment complications of hypofractionated lung SBRT patients at our institution. Materials/Methods: From 2002 to 2010, 44 patients with small primary lung cancer or oligometastasis were treated with SBRT at our institution. All patients were immobilized using a stereotactic body frame, simulated with CT scan and treated with multiple static 6 MV beams. A total of 48 (30 right lung, 17 left lung, 1 mediastinal) lesions were treated, among which 2 patients had 2 lesions and 1 patient had 3 lesions. The median follow-up was 12 (from 1 to 72) months. We exported the composite dose volume histograms (DVHs) of gross target volume (GTV), planning target volume (PTV) and normal lung tissue (whole lung-GTV). For each patient, normal tissue complication probability (NTCP) based on the Poisson model was calculated using the normal lung DVH, and normalized total dose (NTD) volume histograms were generated at 2 Gy fractions with a/ b Z 3.7 Gy to account for different fractionations. Mean dose and V20 (% volume receiving 20Gy) of GTV, PTV and normal lung derived from DVH/ NTDVH were correlated with clinical follow-up. Variable importance for projection (VIP) and correlation coefficient (R) were calculated for each variable using partial least squares regression (PLSR) and logistic regression (LR) to identify the prediction factors for normal tissue complications. Results: There were 2 (4.2%) local failures, 4 (9.1%) grade 2 pneumonitis and 3 (6.8%) radiation-induced fibrosis. The <10% pneumonitis rate is in line with the QUANTEC report for lung SBRT. 5/13 (38.5%) of the lesions in right lower lobe developed complications, in comparison to 1/17 (5.9%) in right upper and middle lobes, 1/5 (20%) in left lower lobe and 0/12 (0%) in left upper lobe. The most influential VIP for predicting the complications were mean GTV dose (VIP Z 1.500, R Z 0.145) and GTV volume (VIP Z 1.451, R Z -0.140), followed by NTCP (VIP Z 1.106, R Z 0.107) although the calculated probability was much higher than the frequency of complications. LR was able to produce a reasonable NTCP curve for these three variables. The predictions factors used for conventional lung RT complications, i.e., V20, VNTD20, mean dose and mean NTD of normal lung had only moderate or low VIP (<0.894), were negatively correlated (R between -0.044 and -0.086) and could not be fit to a NTCP logistic curve. Conclusions: The incidence of radiation induced complications for SBRT increases with the mean GTV dose and cannot be predicted with the known prediction factors for conventional lung RT. The cause for higher probability of complications for right lower lobe is unclear and needs further investigations. NTCP based on Poisson model might be applied to lung SBRT but requires different modeling parameters than that used for conventional lung RT. Author Disclosure: J. Chang: None. B. Wen: None. P. Singh: None. R. Bassalow: None. B. Parashar: None. A.M. Sabbas: None. G.A. Wernicke: None. K.C. Chao: None.
3426 Quantitative Assessment of Lung Function in Stage I and Stage III Lung Radiation Therapy Patients Using 4DCT-based Ventilation Imaging Y. Vinogradskiy,1 G. Gan,1 R. Castillo,2 E. Castillo,2 M. Martel,2 T. Guerrero,2 and M. Miften1; 1University of Colorado School of Medicine, Aurora, CO, 2University of Texas MD Anderson Cancer Center, Houston, TX Purpose/Objective(s): A new and exciting form of imaging is being developed that uses 4-dimensional CT (4DCT) data to create lung ventilation maps. Because 4DCTs are acquired as part of clinical care for lung
3427 Integral Dose Delivered to Normal Brain With Conventional IMRT and Helical Tomotherapy IMRT During Partial Brain Radiation Therapy for High-Grade Gliomas With and Without Selective Sparing of the Hippocampus, Limbic Circuit, and Neural Stem Cell Compartment E. Ziel, A. Diaz, J.C. Marsh, J.A. Wendt, R. Godbole, and J.V. Turian; Rush University Medical Center, Chicago, IL Purpose/Objective(s): To compare the integral dose in joules delivered to normal/uninvolved brain [Jbrain ] during partial brain radiation therapy [PBRT] for high grade glioma patients using helical tomotherapy and 7field traditional inverse planned IMRT using a treatment planning system with and without selective sparing of the contralateral hippocampus, neural stem cell compartment [NSC], and limbic circuit. Materials/Methods: We prepared 4 PBRT plans each for 4 patients with high grade gliomas (46Gy in 23 fractions to PTV46Gy, plus a sequential cone down boost of 14Gy in 7 fractions to PTV60Gy). For all plans a structure denoted “uninvolved brain” was created which included all brain tissue not part of PTV46Gy, PTV60Gy, or standard OAR (eyes, optic nerves, optic chiasm, brainstem). No constraints were included to try to reduce the dose to uninvolved brain in any plan. Selective sparing [SS] plans were prepared with both traditional inverse planned IMRT and helical tomotherapy. In these plans, the contralateral hippocampus, NSC, and limbic circuit were contoured, and constraints
International Journal of Radiation Oncology Biology Physics
3425
cancer patients, calculating ventilation maps from 4DCTs provides spatial lung function information at no extra dosimetric cost to the patient. Studies are underway to validate 4DCT-based ventilation and to use existing 4DCT data to study lung function and optimize treatment plans based on ventilation. The purpose of the current study was to use 4DCT-based ventilation imaging to quantitatively compare lung function between stage I and stage III lung cancer patients. Materials/Methods: Twenty-eight stage I lung cancer patients and 69 stage III lung cancer patients were analyzed. Stage I patients were treated using SBRT and the stage III group were treated using IMRT or 3D-CRT. Each patient had a pre-treatment 4DCT simulation performed as part of treatment planning. The 4DCT data were used to calculate pre-treatment ventilation maps. For each case, a deformable image registration algorithm was used to link corresponding lung volume elements between the inhale and exhale phase of the 4DCT dataset. Following spatial registration, corresponding Hounsfield Units were input into a density-change-based model for quantifying the local ventilation. For each patient, the visually observed ventilation defects were evaluated, the ipsilateral to contralateral ventilation ratio was calculated, and the standard deviation of the ventilation throughout the entire lung was computed. Ventilation metrics were compared between the stage I and stage III groups. Results: Out of 69 stage III patients, 24 (34%) had a visually observed ventilation defect, while 6 (21%) stage I patients had an observed defect. The ipsilateral to contralateral ventilation ratio was 0.97 0.09 for stage I patients, indicating evenly distributed lung function. For stage III patients, the ratio was 0.83 0.05 indicating compromised lung function in the ipsilateral lung. The differences between the groups approached statistical significance (p Z 0.11). The average standard deviation was 0.19 and 0.16 for stage III and stage I patients respectively. The results approached statistical significance (p Z 0.135). Conclusions: Our study uses a new form of ventilation imaging to quantitatively compare lung function between stage I and stage III lung cancer patients. Our data showed differences in lung function between stage I and stage III lung cancer patients. Better understanding of the normal lung function in patients prior to receiving IMRT or SBRT may provide opportunities to lessen the risk of radiation toxicity and assist in personalizing treatment plans in cases where the patient’s baseline lung function is compromised. Author Disclosure: Y. Vinogradskiy: None. G. Gan: None. R. Castillo: None. E. Castillo: None. M. Martel: None. T. Guerrero: None. M. Miften: None.
Analysis of Radiation-induced Toxicity in Patients Receiving Stereotactic Body Radiation Therapy (SBRT) for Lung Tumors J. Chang,1 B. Wen,2 P. Singh,1 R. Bassalow,1 B. Parashar,1 A.M. Sabbas,1 G.A. Wernicke,1 and K.C. Chao1; 1New York Presbyterian - Weill Cornell Medical College, New York, NY, 2Sun Yat-Sen University First Affiliated Hospital, Guangzhou, China Purpose/Objective(s): To analyze and model the treatment complications of hypofractionated lung SBRT patients at our institution. Materials/Methods: From 2002 to 2010, 44 patients with small primary lung cancer or oligometastasis were treated with SBRT at our institution. All patients were immobilized using a stereotactic body frame, simulated with CT scan and treated with multiple static 6 MV beams. A total of 48 (30 right lung, 17 left lung, 1 mediastinal) lesions were treated, among which 2 patients had 2 lesions and 1 patient had 3 lesions. The median follow-up was 12 (from 1 to 72) months. We exported the composite dose volume histograms (DVHs) of gross target volume (GTV), planning target volume (PTV) and normal lung tissue (whole lung-GTV). For each patient, normal tissue complication probability (NTCP) based on the Poisson model was calculated using the normal lung DVH, and normalized total dose (NTD) volume histograms were generated at 2 Gy fractions with a/ b Z 3.7 Gy to account for different fractionations. Mean dose and V20 (% volume receiving 20Gy) of GTV, PTV and normal lung derived from DVH/ NTDVH were correlated with clinical follow-up. Variable importance for projection (VIP) and correlation coefficient (R) were calculated for each variable using partial least squares regression (PLSR) and logistic regression (LR) to identify the prediction factors for normal tissue complications. Results: There were 2 (4.2%) local failures, 4 (9.1%) grade 2 pneumonitis and 3 (6.8%) radiation-induced fibrosis. The <10% pneumonitis rate is in line with the QUANTEC report for lung SBRT. 5/13 (38.5%) of the lesions in right lower lobe developed complications, in comparison to 1/17 (5.9%) in right upper and middle lobes, 1/5 (20%) in left lower lobe and 0/12 (0%) in left upper lobe. The most influential VIP for predicting the complications were mean GTV dose (VIP Z 1.500, R Z 0.145) and GTV volume (VIP Z 1.451, R Z -0.140), followed by NTCP (VIP Z 1.106, R Z 0.107) although the calculated probability was much higher than the frequency of complications. LR was able to produce a reasonable NTCP curve for these three variables. The predictions factors used for conventional lung RT complications, i.e., V20, VNTD20, mean dose and mean NTD of normal lung had only moderate or low VIP (<0.894), were negatively correlated (R between -0.044 and -0.086) and could not be fit to a NTCP logistic curve. Conclusions: The incidence of radiation induced complications for SBRT increases with the mean GTV dose and cannot be predicted with the known prediction factors for conventional lung RT. The cause for higher probability of complications for right lower lobe is unclear and needs further investigations. NTCP based on Poisson model might be applied to lung SBRT but requires different modeling parameters than that used for conventional lung RT. Author Disclosure: J. Chang: None. B. Wen: None. P. Singh: None. R. Bassalow: None. B. Parashar: None. A.M. Sabbas: None. G.A. Wernicke: None. K.C. Chao: None.
3426 Quantitative Assessment of Lung Function in Stage I and Stage III Lung Radiation Therapy Patients Using 4DCT-based Ventilation Imaging Y. Vinogradskiy,1 G. Gan,1 R. Castillo,2 E. Castillo,2 M. Martel,2 T. Guerrero,2 and M. Miften1; 1University of Colorado School of Medicine, Aurora, CO, 2University of Texas MD Anderson Cancer Center, Houston, TX Purpose/Objective(s): A new and exciting form of imaging is being developed that uses 4-dimensional CT (4DCT) data to create lung ventilation maps. Because 4DCTs are acquired as part of clinical care for lung
3427 Integral Dose Delivered to Normal Brain With Conventional IMRT and Helical Tomotherapy IMRT During Partial Brain Radiation Therapy for High-Grade Gliomas With and Without Selective Sparing of the Hippocampus, Limbic Circuit, and Neural Stem Cell Compartment E. Ziel, A. Diaz, J.C. Marsh, J.A. Wendt, R. Godbole, and J.V. Turian; Rush University Medical Center, Chicago, IL Purpose/Objective(s): To compare the integral dose in joules delivered to normal/uninvolved brain [Jbrain ] during partial brain radiation therapy [PBRT] for high grade glioma patients using helical tomotherapy and 7field traditional inverse planned IMRT using a treatment planning system with and without selective sparing of the contralateral hippocampus, neural stem cell compartment [NSC], and limbic circuit. Materials/Methods: We prepared 4 PBRT plans each for 4 patients with high grade gliomas (46Gy in 23 fractions to PTV46Gy, plus a sequential cone down boost of 14Gy in 7 fractions to PTV60Gy). For all plans a structure denoted “uninvolved brain” was created which included all brain tissue not part of PTV46Gy, PTV60Gy, or standard OAR (eyes, optic nerves, optic chiasm, brainstem). No constraints were included to try to reduce the dose to uninvolved brain in any plan. Selective sparing [SS] plans were prepared with both traditional inverse planned IMRT and helical tomotherapy. In these plans, the contralateral hippocampus, NSC, and limbic circuit were contoured, and constraints