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Predictors of Rib Fracture and Nonfracture Chest Wall Pain After Lung Stereotactic Body Radiation Therapy (SBRT)
Volume 84 Number 3S Supplement 2012
Poster Viewing Abstracts S601
volumes covered by the 5Gy and 20Gy isodose lines (i.e. V5 and V20, respectively). Materials/Methods: Five patients with lower lobe tumors (greatest excursion due to respiratory motion) previously treated with SBRT at our institution were chosen for this study. A dynamic conformal arc technique was employed through the MM3 collimator on a linear accelerator. The PTV in the original plan had an average of 90.4cc (7.7 cc - 221.9cc). The original planned V20 averaged 4.1% (1%-11.6%) while V5 averaged 19.9% (6.7% - 37.5%) of normal lung volumes. Based on a survey of published data and the reported mean reductions in cranio-caudal ITV extent second to application of abdominal compression, we systematically reduced the ITV/PTV for each patient along the cranio-caudal (CC) direction by 6, 8 and 10 mm (i.e., 3, 4 and 5mm at each end). No change was made in the anterior-posterior or left-right directions. Plans were then created for each of the new PTVs using the same conformal arc extent as the original plan, and all plans were normalized such that 95% of the PTV received the prescription dose. In each case, the value of V5 and V20 for the new plan was compared with those from the original plan. Poster Viewing Abstract 3017; Table Effects of Decreasing ITV/PTV Size on the Values of V5 and V20 for the Lung ITV/PTV ITV/PTV ITV/PTV ITV/PTV ITV/PTV ITV/PTV shrunk by shrunk by shrunk by shrunk by shrunk by shrunk by 10 mm 10 mm 8 mm 8 mm 6 mm 6 mm
Average Minimum Maximum
Decrease in V5 (%)
Decrease in V20 (%)
Decrease in V5 (%)
Decrease in V20 (%)
Decrease in V5 (%)
Decrease in V20 (%)
1.7 0.9 3.1
0.4 0.0 1.1
2.6 1.3 4.7
1.0 0.3 2.0
3.5 2.0 5.9
1.1 0.4 2.5
Results: The Table shows the average, minimum and maximum decrease in V5 and V20 for each of the 3 scenarios investigated here. Conclusions: As expected, the value of V5 and V20 decreased when the PTV was reduced, with the magnitude of the decrease being larger the more the PTV size was decreased. However, the observed reduction of V5 and V20 was modest, even when the PTV was reduced by 10 mm, with the maximum drop in V5 and V20 being 5.9% and 2.5% respectively. This suggests that, for the conformal arc technique evaluated here, anticipation of significant reduction in V5 and V20 may not be a reasonable sole motivation for application of abdominal compression. Author Disclosure: V. Sarkar: None. B. Wang: None. P. Rassiah-Szegedi: None. H. Zhao: None. J.Y. Huang: None. M.W. Szegedi: None. Y.J. Hitchcock: None. K.E. Kokeny: None. B.J. Salter: None.
3018 Quantitative Evaluation of Impact Upon Tumor Control Probability (TCP) From Quality Assurance Criteria for Non-small Cell Lung Cancer From RTOG 1106 Study W. Chen,1 Y. Cui,1 F. Kong,2 M. Machtay,3 G. Videtic,4 B. Loo,5 E. Gore,6 J. Galvin,7 Y. Yan,1 and Y. Xiao7; 1Thomas Jefferson University Hospital, Philadelphia, PA, 2University of Michigan, Ann Arbor, MI, 3Case Medical Center, Cleveland, OH, 4Cleveland Clinic, Cleveland, OH, 5Department of Radiation Oncology and Stanford Cancer Institute, Stanford University, Stanford, CA, 6Medical College Wisconsin, Milwaukee, WI, 7Radiation Therapy Oncology Group, Philadelphia, PA Purpose/Objective(s): Adaptive radiation therapy (ART), which involves modifying the radiation plan for the target as it changes during therapy, is being explored for diseases such as lung cancer. Approximations are made in the protocol that organs-at-risk (OARs) remain constant in shape and relative location during ART. In this study, we investigate the accuracy of this assumption, volumetrically and dosimetrically. Materials/Methods: RTOG 1106 is a randomized Phase II Trial of Individualized Radiation therapy Using During-Treatment FDG-PET/CT (DurCT) and Modern Technology in Locally Advanced Non-Small Cell Lung Cancer (NSCLC). In the lead up to the study pre-clinical planning test
cases were given to several institutions to study feasibility and consistency in contouring the target and OARs, and to generate treatment plans meeting predefined criteria. After the initial plan of around 50Gy, a “highest achievable dose” adaptive plan was generated using the target defined on CT acquired during the course of the treatment (Dur-CT). Targets are re-defined but not the OARs. In this study, we generate OARs for the adaptive course by deforming OAR contours from the Pre-CT to Dur-CT with visual validation. These contours were then transferred back to Pre-CT for dosimetry assessments. Results: We evaluated dosimetric and volumetric parameters for three major OARs - cord, heart and lung from four institutions between pre-CT and dur-CT. There were significant volumetric variations: for cord, the volume difference ranged from 2.11% to 3.25% (2.51%0.45%). For heart, it ranged from 25.73% to 28.84% (26.82%1.34%). For lung, it ranges from 10.5% to 11.9% (11.06%0.53%). There were also significant dosimetric variations when we applied the adaptive plan to the deformed and non-deformed OARs. For cord, the mean dose percentage change ranged from 16.07% to 19.63% (17.65%1.53%); for heart, that ranged from 8.62% to 13.14% (9.78%2.02%); for lung, that ranged from 8.01% to 11.04% (10.53%0.44%). For cord, the max dose percentage change ranged from 6.04% to 16.14% (11.39%3.64%); for heart, that ranged from 0.36% to 3.15% (1.45%1.08%); for lung, that ranged from 0.59% to 2.86% (1.48%0.86%). Conclusions: Significant TCP variations were observed even from dosimetric variations meeting heuristic QA criteria. The target definition variation between clinicians is still a significant factor. The PTV expansion mitigates the dosimetric variations within QA tolerances. The solutions may be to require more stringent QA criteria and/or take these uncertainties into consideration explicitly in the PTV design. This work is supported by RTOG grant U10 CA21661 from the NCI and Pennsylvania Department of Health 2008 Formula Grant 4100047624. Author Disclosure: W. Chen: None. Y. Cui: None. F. Kong: None. M. Machtay: None. G. Videtic: None. B. Loo: None. E. Gore: None. J. Galvin: None. Y. Yan: None. Y. Xiao: None.
3019 Predictors of Rib Fracture and Nonfracture Chest Wall Pain After Lung Stereotactic Body Radiation Therapy (SBRT) J. Lee, K. Creach, A. Bierhals, T. DeWees, D. Mullen, P. Parikh, J. Bradley, and C. Robinson; Washington University, St Louis, MO Purpose/Objective(s): Rib fracture (fracture) and non-fracture related chest wall pain (CW pain) have been described after lung SBRT, but are typically combined for purposes of toxicity analysis despite having potentially different mechanisms for development. We sought to describe the natural history of fracture vs CW pain after lung SBRT, and identify patient, tumor, dosimetric and radiologic factors associated with their development. Materials/Methods: From an IRB approved institutional registry, we identified 123 lung lesions in 118 patients treated with SBRT to 54 Gy in 3 fractions from 2004-2009. Fracture and CW pain were identified by medical chart review. An independent radiologist verified fractures on chest CT and noted any findings of chest wall edema or rib radiation necrosis. Electronic treatment plans were available for 74 CWs, which were contoured as a 3 cm expansion from involved lung. Cox and Kaplan Meier (KM) log-rank uni/multivariate analyses evaluated patient (age, sex, Zubrod, diabetes, BMI, smoking, connective tissue disorder [CTD]), tumor (PTV volume and max dimension) and dosimetric factors (conformality index, gradient, max CW dose, absolute/relative CW V20 to 65Gy) for association with CW toxicity. Results: Median follow-up was 30.4 mo. CW pain occurred in 32 patients (27.7%) at a median of 8.2 mo. Of these, 22 had G1, 8 had G2 and 2 had G3 CW pain. Fractures occurred in 24 patients (20.3%) at a median of 14.5 mo. Nine had asymptomatic fractures, 10 had G1, 4 had G2 and 1 had G3 fracture pain. Of those with fractures, 20 (83.3%) had radiographic chest wall edema and 11 (45.8%) had rib radiation necrosis on chest CT. Chest wall edema predated fracture by a median of 6.9 mo. Rib radiation necrosis
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tended to appear after fractures a median of 12.8 mo later. Female sex (pZ0.05), CTD (pZ0.004), and PTV volume (pZ0.03) were associated with CW pain on univariate analysis. Likewise, a trend was noted for the relative CW V20Gy (pZ0.085), V25Gy (pZ0.06) and V30Gy (pZ0.074). On multivariate analysis, female sex (pZ0.013) and PTV volume (pZ0.005) remained significantly associated with CW pain. Only female sex (pZ0.007) was significantly associated with fracture. Of the 60 women in this study, 21 (35%) had CW pain and 19 (31.7%) had fracture after SBRT. Of the 63 men, 11 (17.5%) had CW pain and 5 (7.9%) had fracture. Conclusions: After lung SBRT, rib fracture occurs a median of 6 months after non-fracture related CW pain. While both are associated with female sex, CW pain is additionally correlated with CTD and PTV volume and trended towards significance for V20-30Gy to the CW. Most fractures are preceded by radiographic chest wall edema by > 6 months. Our results demonstrate that fracture and CW pain after lung SBRT often occur independently, possibly with distinct pathophysiologies. Author Disclosure: J. Lee: None. K. Creach: None. A. Bierhals: None. T. DeWees: None. D. Mullen: None. P. Parikh: None. J. Bradley: None. C. Robinson: None.
Conclusions: There are significant variations between initial OARs and OARs contoured from subsequent images, resulting in substantial deviations in dosimetry. Therefore, for precise adaptive planning, re-segmentation of OARs on subsequent images is recommended. Deformable registration can be used to facilitate the process. Acknowledgment: This work is supported by RTOG grant U10 CA21661 from the NCI and Pennsylvania Department of Health 2008 Formula Grant 4100047624. Author Disclosure: W. Chen: None. Y. Cui: None. F. Kong: None. M. Machtay: None. G. Videtic: None. B. Loo: None. E. Gore: None. J. Galvin: None. Y. Yu: None. Y. Xiao: None.
3020 Is Recontouring Organs-at-Risk (OAR) for Adaptive Radiation Therapy Plans for Locally Advanced Lung Cancer Necessary? A Preactivation Analysis From Radiation Therapy Oncology Group (RTOG) 1106 W. Chen,1 Y. Cui,1 F. Kong,2 M. Machtay,3 G. Videtic,4 B. Loo,5 E. Gore,6 J. Galvin,7 Y. Yu,1 and Y. Xiao7; 1Thomas Jefferson University Hospital, Philadelphia, PA, 2University of Michigan, Ann Arbor, MI, 3Case Medical Center, Cleveland, OH, 4Cleveland Clinic, Cleveland, OH, 5Department of Radiation Oncology and Stanford Cancer Institute, Stanford University, Stanford, CA, 6Medical College Wisconsin, Milwaukee, WI, 7Radiation Therapy Oncology Group, Philadelphia, PA Purpose/Objective(s): Adaptive radiation therapy (ART), which involves modifying the radiation plan for the target as it changes during therapy, is being explored for diseases such as lung cancer. Approximations are made in the protocol that organs-at-risk (OARs) remain constant in shape and relative location during ART. In this study, we investigate the accuracy of this assumption, volumetrically and dosimetrically. Materials/Methods: RTOG 1106 is a randomized Phase II Trial of Individualized Radiation therapy Using During-Treatment FDG-PET/CT (DurCT) and Modern Technology in Locally Advanced Non-Small Cell Lung Cancer (NSCLC). In the lead up to the study pre-clinical planning test cases were given to several institutions to study feasibility and consistency in contouring the target and OARs, and to generate treatment plans meeting predefined criteria. After the initial plan of around 50Gy, a “highest achievable dose” adaptive plan was generated using the target defined on CT acquired during the course of the treatment (Dur-CT). Targets are re-defined but not the OARs. In this study, we generate OARs for the adaptive course by deforming OAR contours from the Pre-CT to Dur-CT with visual validation. These contours were then transferred back to Pre-CT for dosimetry assessments. Results: We evaluated dosimetric and volumetric parameters for three major OARs - cord, heart and lung from four institutions between pre-CT and dur-CT. There were significant volumetric variations: for cord, the volume difference ranged from 2.11% to 3.25% (2.51%0.45%). For heart, it ranged from 25.73% to 28.84% (26.82%1.34%). For lung, it ranges from 10.5% to 11.9% (11.06%0.53%). There were also significant dosimetric variations when we applied the adaptive plan to the deformed and non-deformed OARs. For cord, the mean dose percentage change ranged from 16.07% to 19.63% (17.65%1.53%); for heart, that ranged from 8.62% to 13.14% (9.78%2.02%); for lung, that ranged from 8.01% to 11.04% (10.53%0.44%). For cord, the max dose percentage change ranged from 6.04% to 16.14% (11.39%3.64%); for heart, that ranged from 0.36% to 3.15% (1.45%1.08%); for lung, that ranged from 0.59% to 2.86% (1.48%0.86%).
3021 Salvage Stereotactic Body Radiation Therapy (SBRT) for Local Failure After Upfront Lung SBRT: If at First you Don’t Succeed. J. Hearn, G.M. Videtic, T. Djemil, and K.L. Stephans; Cleveland Clinic, Cleveland, OH Purpose/Objective(s): When local failure occurs after definitive stereotactic body radiation therapy (SBRT) for medically inoperable patients with early-stage non-small cell lung cancer (NSCLC) the optimal treatment strategy is unclear. Surgical salvage is not indicated given the patient’s de facto inoperable status. In select cases we have used repeat SBRT as salvage therapy. The purpose of the present report is to review the results of our experience to date. Materials/Methods: For the interval from August 2004 through October 2010 we reviewed our IRB-approved lung SBRT registry and selected all patients with local failure only. Failure was defined by PET with or without biopsy. All patients were treated on a system using Exactrac for IGRT. Tumor motion control involved a Bodyfix vacuum system for immobilization along with abdominal compression. SBRT schedules employed were at the physician’s discretion and all had a BED>100 Gy10. Results: Of 350 lesions treated, 17 lesions in 17 patients demonstrated isolated local failure (4.9%). Of these, 6 received repeat SBRT as salvage therapy, whereas the remaining 11 did not, due to excessive lesion size (>8cm), proximity to esophagus or chest wall, pre-SBRT conventional radiation, severe medical comorbidity/rapid clinical deterioration, or persistent chest wall pain from initial SBRT. Initial SBRT schedule for 5 patients was 50 Gy/5 fractions (fx) and 30 Gy/1 fx for one. Salvage SBRT schedule for 5 patients was 50 Gy/5 fx and 60 Gy/3 fx for one. One patient received adjuvant chemotherapy after salvage SBRT. Median tumor size at initial treatment and at recurrence was 2.7 cm (range: 1.3-4.5 cm) and 3.55 cm (range: 1.7-4.8 cm), respectively. Two lesions were central, while the remainder were peripheral. At salvage SBRT, median age was 70 with median KPS of 80. At analysis, two patients have died from progressive disease, one 5.3 months after salvage SBRT and the other after 31.7 months. Of the remaining 4 patients, 1 has persistent local-only disease 9.5 months after salvage SBRT, while 3 are disease-free as of last follow up (9.1-18.2 months from salvage). Concerning toxicity from salvage SBRT, 2 patients had grade 2 chest wall pain and 1 patient had grade 2 fatigue. There were no grade 3 or higher toxicities. Conclusions: Repeat SBRT with BED >100 Gy10 after local failure in patients with early-stage NSCLC appears to be well tolerated and may be a reasonable salvage strategy for post-SBRT local failures. Author Disclosure: J. Hearn: None. G.M. Videtic: None. T. Djemil: None. K.L. Stephans: None.
3022 The Role of Pretreatment PET/CT Parameters in Predicting Response After Lung Cancer Treatment A. Lavaf, A. Tejwani, P. Daya, M. Atia, and H. Ashamalla; New York Methodist Hospital, Brooklyn, NY Purpose/Objective(s): While PET/CT has been validated in lung cancer staging, its utility in radiation therapy treatment planning and predicting response are still investigational. The objective of this study was to
Poster Viewing Abstracts S601
volumes covered by the 5Gy and 20Gy isodose lines (i.e. V5 and V20, respectively). Materials/Methods: Five patients with lower lobe tumors (greatest excursion due to respiratory motion) previously treated with SBRT at our institution were chosen for this study. A dynamic conformal arc technique was employed through the MM3 collimator on a linear accelerator. The PTV in the original plan had an average of 90.4cc (7.7 cc - 221.9cc). The original planned V20 averaged 4.1% (1%-11.6%) while V5 averaged 19.9% (6.7% - 37.5%) of normal lung volumes. Based on a survey of published data and the reported mean reductions in cranio-caudal ITV extent second to application of abdominal compression, we systematically reduced the ITV/PTV for each patient along the cranio-caudal (CC) direction by 6, 8 and 10 mm (i.e., 3, 4 and 5mm at each end). No change was made in the anterior-posterior or left-right directions. Plans were then created for each of the new PTVs using the same conformal arc extent as the original plan, and all plans were normalized such that 95% of the PTV received the prescription dose. In each case, the value of V5 and V20 for the new plan was compared with those from the original plan. Poster Viewing Abstract 3017; Table Effects of Decreasing ITV/PTV Size on the Values of V5 and V20 for the Lung ITV/PTV ITV/PTV ITV/PTV ITV/PTV ITV/PTV ITV/PTV shrunk by shrunk by shrunk by shrunk by shrunk by shrunk by 10 mm 10 mm 8 mm 8 mm 6 mm 6 mm
Average Minimum Maximum
Decrease in V5 (%)
Decrease in V20 (%)
Decrease in V5 (%)
Decrease in V20 (%)
Decrease in V5 (%)
Decrease in V20 (%)
1.7 0.9 3.1
0.4 0.0 1.1
2.6 1.3 4.7
1.0 0.3 2.0
3.5 2.0 5.9
1.1 0.4 2.5
Results: The Table shows the average, minimum and maximum decrease in V5 and V20 for each of the 3 scenarios investigated here. Conclusions: As expected, the value of V5 and V20 decreased when the PTV was reduced, with the magnitude of the decrease being larger the more the PTV size was decreased. However, the observed reduction of V5 and V20 was modest, even when the PTV was reduced by 10 mm, with the maximum drop in V5 and V20 being 5.9% and 2.5% respectively. This suggests that, for the conformal arc technique evaluated here, anticipation of significant reduction in V5 and V20 may not be a reasonable sole motivation for application of abdominal compression. Author Disclosure: V. Sarkar: None. B. Wang: None. P. Rassiah-Szegedi: None. H. Zhao: None. J.Y. Huang: None. M.W. Szegedi: None. Y.J. Hitchcock: None. K.E. Kokeny: None. B.J. Salter: None.
3018 Quantitative Evaluation of Impact Upon Tumor Control Probability (TCP) From Quality Assurance Criteria for Non-small Cell Lung Cancer From RTOG 1106 Study W. Chen,1 Y. Cui,1 F. Kong,2 M. Machtay,3 G. Videtic,4 B. Loo,5 E. Gore,6 J. Galvin,7 Y. Yan,1 and Y. Xiao7; 1Thomas Jefferson University Hospital, Philadelphia, PA, 2University of Michigan, Ann Arbor, MI, 3Case Medical Center, Cleveland, OH, 4Cleveland Clinic, Cleveland, OH, 5Department of Radiation Oncology and Stanford Cancer Institute, Stanford University, Stanford, CA, 6Medical College Wisconsin, Milwaukee, WI, 7Radiation Therapy Oncology Group, Philadelphia, PA Purpose/Objective(s): Adaptive radiation therapy (ART), which involves modifying the radiation plan for the target as it changes during therapy, is being explored for diseases such as lung cancer. Approximations are made in the protocol that organs-at-risk (OARs) remain constant in shape and relative location during ART. In this study, we investigate the accuracy of this assumption, volumetrically and dosimetrically. Materials/Methods: RTOG 1106 is a randomized Phase II Trial of Individualized Radiation therapy Using During-Treatment FDG-PET/CT (DurCT) and Modern Technology in Locally Advanced Non-Small Cell Lung Cancer (NSCLC). In the lead up to the study pre-clinical planning test
cases were given to several institutions to study feasibility and consistency in contouring the target and OARs, and to generate treatment plans meeting predefined criteria. After the initial plan of around 50Gy, a “highest achievable dose” adaptive plan was generated using the target defined on CT acquired during the course of the treatment (Dur-CT). Targets are re-defined but not the OARs. In this study, we generate OARs for the adaptive course by deforming OAR contours from the Pre-CT to Dur-CT with visual validation. These contours were then transferred back to Pre-CT for dosimetry assessments. Results: We evaluated dosimetric and volumetric parameters for three major OARs - cord, heart and lung from four institutions between pre-CT and dur-CT. There were significant volumetric variations: for cord, the volume difference ranged from 2.11% to 3.25% (2.51%0.45%). For heart, it ranged from 25.73% to 28.84% (26.82%1.34%). For lung, it ranges from 10.5% to 11.9% (11.06%0.53%). There were also significant dosimetric variations when we applied the adaptive plan to the deformed and non-deformed OARs. For cord, the mean dose percentage change ranged from 16.07% to 19.63% (17.65%1.53%); for heart, that ranged from 8.62% to 13.14% (9.78%2.02%); for lung, that ranged from 8.01% to 11.04% (10.53%0.44%). For cord, the max dose percentage change ranged from 6.04% to 16.14% (11.39%3.64%); for heart, that ranged from 0.36% to 3.15% (1.45%1.08%); for lung, that ranged from 0.59% to 2.86% (1.48%0.86%). Conclusions: Significant TCP variations were observed even from dosimetric variations meeting heuristic QA criteria. The target definition variation between clinicians is still a significant factor. The PTV expansion mitigates the dosimetric variations within QA tolerances. The solutions may be to require more stringent QA criteria and/or take these uncertainties into consideration explicitly in the PTV design. This work is supported by RTOG grant U10 CA21661 from the NCI and Pennsylvania Department of Health 2008 Formula Grant 4100047624. Author Disclosure: W. Chen: None. Y. Cui: None. F. Kong: None. M. Machtay: None. G. Videtic: None. B. Loo: None. E. Gore: None. J. Galvin: None. Y. Yan: None. Y. Xiao: None.
3019 Predictors of Rib Fracture and Nonfracture Chest Wall Pain After Lung Stereotactic Body Radiation Therapy (SBRT) J. Lee, K. Creach, A. Bierhals, T. DeWees, D. Mullen, P. Parikh, J. Bradley, and C. Robinson; Washington University, St Louis, MO Purpose/Objective(s): Rib fracture (fracture) and non-fracture related chest wall pain (CW pain) have been described after lung SBRT, but are typically combined for purposes of toxicity analysis despite having potentially different mechanisms for development. We sought to describe the natural history of fracture vs CW pain after lung SBRT, and identify patient, tumor, dosimetric and radiologic factors associated with their development. Materials/Methods: From an IRB approved institutional registry, we identified 123 lung lesions in 118 patients treated with SBRT to 54 Gy in 3 fractions from 2004-2009. Fracture and CW pain were identified by medical chart review. An independent radiologist verified fractures on chest CT and noted any findings of chest wall edema or rib radiation necrosis. Electronic treatment plans were available for 74 CWs, which were contoured as a 3 cm expansion from involved lung. Cox and Kaplan Meier (KM) log-rank uni/multivariate analyses evaluated patient (age, sex, Zubrod, diabetes, BMI, smoking, connective tissue disorder [CTD]), tumor (PTV volume and max dimension) and dosimetric factors (conformality index, gradient, max CW dose, absolute/relative CW V20 to 65Gy) for association with CW toxicity. Results: Median follow-up was 30.4 mo. CW pain occurred in 32 patients (27.7%) at a median of 8.2 mo. Of these, 22 had G1, 8 had G2 and 2 had G3 CW pain. Fractures occurred in 24 patients (20.3%) at a median of 14.5 mo. Nine had asymptomatic fractures, 10 had G1, 4 had G2 and 1 had G3 fracture pain. Of those with fractures, 20 (83.3%) had radiographic chest wall edema and 11 (45.8%) had rib radiation necrosis on chest CT. Chest wall edema predated fracture by a median of 6.9 mo. Rib radiation necrosis
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tended to appear after fractures a median of 12.8 mo later. Female sex (pZ0.05), CTD (pZ0.004), and PTV volume (pZ0.03) were associated with CW pain on univariate analysis. Likewise, a trend was noted for the relative CW V20Gy (pZ0.085), V25Gy (pZ0.06) and V30Gy (pZ0.074). On multivariate analysis, female sex (pZ0.013) and PTV volume (pZ0.005) remained significantly associated with CW pain. Only female sex (pZ0.007) was significantly associated with fracture. Of the 60 women in this study, 21 (35%) had CW pain and 19 (31.7%) had fracture after SBRT. Of the 63 men, 11 (17.5%) had CW pain and 5 (7.9%) had fracture. Conclusions: After lung SBRT, rib fracture occurs a median of 6 months after non-fracture related CW pain. While both are associated with female sex, CW pain is additionally correlated with CTD and PTV volume and trended towards significance for V20-30Gy to the CW. Most fractures are preceded by radiographic chest wall edema by > 6 months. Our results demonstrate that fracture and CW pain after lung SBRT often occur independently, possibly with distinct pathophysiologies. Author Disclosure: J. Lee: None. K. Creach: None. A. Bierhals: None. T. DeWees: None. D. Mullen: None. P. Parikh: None. J. Bradley: None. C. Robinson: None.
Conclusions: There are significant variations between initial OARs and OARs contoured from subsequent images, resulting in substantial deviations in dosimetry. Therefore, for precise adaptive planning, re-segmentation of OARs on subsequent images is recommended. Deformable registration can be used to facilitate the process. Acknowledgment: This work is supported by RTOG grant U10 CA21661 from the NCI and Pennsylvania Department of Health 2008 Formula Grant 4100047624. Author Disclosure: W. Chen: None. Y. Cui: None. F. Kong: None. M. Machtay: None. G. Videtic: None. B. Loo: None. E. Gore: None. J. Galvin: None. Y. Yu: None. Y. Xiao: None.
3020 Is Recontouring Organs-at-Risk (OAR) for Adaptive Radiation Therapy Plans for Locally Advanced Lung Cancer Necessary? A Preactivation Analysis From Radiation Therapy Oncology Group (RTOG) 1106 W. Chen,1 Y. Cui,1 F. Kong,2 M. Machtay,3 G. Videtic,4 B. Loo,5 E. Gore,6 J. Galvin,7 Y. Yu,1 and Y. Xiao7; 1Thomas Jefferson University Hospital, Philadelphia, PA, 2University of Michigan, Ann Arbor, MI, 3Case Medical Center, Cleveland, OH, 4Cleveland Clinic, Cleveland, OH, 5Department of Radiation Oncology and Stanford Cancer Institute, Stanford University, Stanford, CA, 6Medical College Wisconsin, Milwaukee, WI, 7Radiation Therapy Oncology Group, Philadelphia, PA Purpose/Objective(s): Adaptive radiation therapy (ART), which involves modifying the radiation plan for the target as it changes during therapy, is being explored for diseases such as lung cancer. Approximations are made in the protocol that organs-at-risk (OARs) remain constant in shape and relative location during ART. In this study, we investigate the accuracy of this assumption, volumetrically and dosimetrically. Materials/Methods: RTOG 1106 is a randomized Phase II Trial of Individualized Radiation therapy Using During-Treatment FDG-PET/CT (DurCT) and Modern Technology in Locally Advanced Non-Small Cell Lung Cancer (NSCLC). In the lead up to the study pre-clinical planning test cases were given to several institutions to study feasibility and consistency in contouring the target and OARs, and to generate treatment plans meeting predefined criteria. After the initial plan of around 50Gy, a “highest achievable dose” adaptive plan was generated using the target defined on CT acquired during the course of the treatment (Dur-CT). Targets are re-defined but not the OARs. In this study, we generate OARs for the adaptive course by deforming OAR contours from the Pre-CT to Dur-CT with visual validation. These contours were then transferred back to Pre-CT for dosimetry assessments. Results: We evaluated dosimetric and volumetric parameters for three major OARs - cord, heart and lung from four institutions between pre-CT and dur-CT. There were significant volumetric variations: for cord, the volume difference ranged from 2.11% to 3.25% (2.51%0.45%). For heart, it ranged from 25.73% to 28.84% (26.82%1.34%). For lung, it ranges from 10.5% to 11.9% (11.06%0.53%). There were also significant dosimetric variations when we applied the adaptive plan to the deformed and non-deformed OARs. For cord, the mean dose percentage change ranged from 16.07% to 19.63% (17.65%1.53%); for heart, that ranged from 8.62% to 13.14% (9.78%2.02%); for lung, that ranged from 8.01% to 11.04% (10.53%0.44%). For cord, the max dose percentage change ranged from 6.04% to 16.14% (11.39%3.64%); for heart, that ranged from 0.36% to 3.15% (1.45%1.08%); for lung, that ranged from 0.59% to 2.86% (1.48%0.86%).
3021 Salvage Stereotactic Body Radiation Therapy (SBRT) for Local Failure After Upfront Lung SBRT: If at First you Don’t Succeed. J. Hearn, G.M. Videtic, T. Djemil, and K.L. Stephans; Cleveland Clinic, Cleveland, OH Purpose/Objective(s): When local failure occurs after definitive stereotactic body radiation therapy (SBRT) for medically inoperable patients with early-stage non-small cell lung cancer (NSCLC) the optimal treatment strategy is unclear. Surgical salvage is not indicated given the patient’s de facto inoperable status. In select cases we have used repeat SBRT as salvage therapy. The purpose of the present report is to review the results of our experience to date. Materials/Methods: For the interval from August 2004 through October 2010 we reviewed our IRB-approved lung SBRT registry and selected all patients with local failure only. Failure was defined by PET with or without biopsy. All patients were treated on a system using Exactrac for IGRT. Tumor motion control involved a Bodyfix vacuum system for immobilization along with abdominal compression. SBRT schedules employed were at the physician’s discretion and all had a BED>100 Gy10. Results: Of 350 lesions treated, 17 lesions in 17 patients demonstrated isolated local failure (4.9%). Of these, 6 received repeat SBRT as salvage therapy, whereas the remaining 11 did not, due to excessive lesion size (>8cm), proximity to esophagus or chest wall, pre-SBRT conventional radiation, severe medical comorbidity/rapid clinical deterioration, or persistent chest wall pain from initial SBRT. Initial SBRT schedule for 5 patients was 50 Gy/5 fractions (fx) and 30 Gy/1 fx for one. Salvage SBRT schedule for 5 patients was 50 Gy/5 fx and 60 Gy/3 fx for one. One patient received adjuvant chemotherapy after salvage SBRT. Median tumor size at initial treatment and at recurrence was 2.7 cm (range: 1.3-4.5 cm) and 3.55 cm (range: 1.7-4.8 cm), respectively. Two lesions were central, while the remainder were peripheral. At salvage SBRT, median age was 70 with median KPS of 80. At analysis, two patients have died from progressive disease, one 5.3 months after salvage SBRT and the other after 31.7 months. Of the remaining 4 patients, 1 has persistent local-only disease 9.5 months after salvage SBRT, while 3 are disease-free as of last follow up (9.1-18.2 months from salvage). Concerning toxicity from salvage SBRT, 2 patients had grade 2 chest wall pain and 1 patient had grade 2 fatigue. There were no grade 3 or higher toxicities. Conclusions: Repeat SBRT with BED >100 Gy10 after local failure in patients with early-stage NSCLC appears to be well tolerated and may be a reasonable salvage strategy for post-SBRT local failures. Author Disclosure: J. Hearn: None. G.M. Videtic: None. T. Djemil: None. K.L. Stephans: None.
3022 The Role of Pretreatment PET/CT Parameters in Predicting Response After Lung Cancer Treatment A. Lavaf, A. Tejwani, P. Daya, M. Atia, and H. Ashamalla; New York Methodist Hospital, Brooklyn, NY Purpose/Objective(s): While PET/CT has been validated in lung cancer staging, its utility in radiation therapy treatment planning and predicting response are still investigational. The objective of this study was to