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Risk of Pneumonitis After Stereotactic Body Radiation Therapy for Non-Small Cell Lung Cancer in Patients With Prior Anatomic Resection
S662
International Journal of Radiation Oncology Biology Physics
offering an acceptable overlap with expert drawn contours and almost halving the target volumes segmentation time. Author Disclosure: C. Valentini: None. L. Boldrini: None. G. Chiloiro: None. G.C. Mattiucci: None. G. Mantini: None. D. Pasini: None. N. Dinapoli: None. S. Chiesa: None. N. Caria: None. V. Valentini: None.
known to decrease treatment time as compared to treatments with the flattening filter (FF) due to a higher dose rate. FFF beams are also thought to have a sharper penumbra, less collimator scatter, reduced leaf transmission, and reduced head leakage. Due to the addition of low energy bremsstrahlung tail, the number of degrees of freedom allowed in planning is also increased. We performed an inter-institutional dosimetric study of FFF versus FF beams for patients eligible for either RTOG 0915 (20 patients) or RTOG 0813 (10 patients) within established protocol criteria to determine if any statistically significant dosimetric advantages/disadvantages were seen. Materials/Methods: Both FFF and FF SBRT plans were generated for thirty lung cancer patients from two institutions with a mean PTV volume of 55.5 cc (STD 46.1 cc). All patient plans consisted of two to four full or partial arcs with up to 15 couch kicks. Parameters of interest included prescription isodose surface coverage, target dose heterogeneity, high dose spillage (location and volume), low dose spillage (location and volume), lung dose spillage, and critical structure maximum and volumetric dose limits. Results: For conformality criteria, we observed equivalent or higher conformality for FFF plans with both 0915 and 0813 patient cohorts. However, statistically significant results for conformality were observed in the 0915 patient group. Observed percentage reductions (mean, STD, p-value) were: High dose spillage location (0.09%, 0.17%, 0.029), high dose spillage volume (0.98%, 1.67%, 0.016), and low dose spillage volume (2.83%, 3.42%, 0.001). Furthermore, both 0915 and 0813 patient cohorts had statistically significant reductions to the total lung volume receiving doses between 11.6 -20.0 Gy. Observed percentage reductions (mean, STD, p-value) were: 0915-V20 (2.25%, 3.12%, 0.004), 0915-V12.4 (2.1%, 1.8%, 0.001), 0915-V11.6 (2.1%, 1.53%, 0.001), 0813-V20 (3.63%, 2.97%, 0.004), 0813-V13.5 (4.47%, 4.48%, 0.04), and 0813-V12.5 (4.29%, 4.61%, 0.04). As expected, skin dose was higher in the FFF plans for both groups (2.34%, 3.0%, 0.02). Conclusions: Our work represents the first comparison of FFF and FF modes using complete RTOG lung SBRT dosimetric parameters. We demonstrate that in addition to shorter treatment times, there are statistically significant dosimetric advantages to using FFF beams for lung SBRT, namely increased dose conformality and decreased low dose lung spillage. Author Disclosure: B.W. Maidment III: None. C. Geesey: None. C. Xie: None. J. Chinault: None. R. Best: None. J.M. Larner: None. K. Wijesooriya: None.
3144 Risk of Pneumonitis After Stereotactic Body Radiation Therapy for Non-Small Cell Lung Cancer in Patients With Prior Anatomic Resection J.T. Hayes,1 A.M. Chen,2 and M.E. Daly1; 1UC Davis Cancer Center, Sacramento, CA, 2University of California, Los Angeles, Los Angeles, CA Purpose/Objective(s): Stereotactic body radiation therapy (SBRT) has emerged as a standard treatment option for early stage, medically inoperable non-small cell lung cancer (NSCLC). Dosimetric factors including lung volume receiving 20 Gy (V20) >10%and mean lung dose (MLD) >4 Gy are established risk factors for radiation pneumonitis (RP) following SBRT, but limited data evaluate the relative risk of RP in patients undergoing SBRT following prior anatomic lung resection (ALR). This study assessed the incidence of RP and all grade 2+ pulmonary toxicity in patients treated with SBRT for NSCLC following ALR and compare toxicity rates to patients without prior ALR. Materials/Methods: The medical records of 83 consecutive patients with T1-T3 NSCLC treated with 87 courses of SBRT for 93 lung tumors (16 central, 77 peripheral) between January 2007 and September 2013 were reviewed. Sixteen patients with a history of prior ALR were identified, including lobectomy (n Z 12), bilobectomy (n Z 1), and pneumonectomy (n Z 3), with 67 patients without history of prior ALD. The most commonly used fractionation regimen was 50Gy in 5 fractions. Toxicities were graded according to the Common Terminology Criteria for Adverse Events (CTCAE) v.4.0. Rates of grade 2+ RP and any grade 2+ pulmonary toxicity were compared between patients with and without prior ALR. Crude rates of RP and all grade 2+ pulmonary toxicity were compared using Fisher’s exact test. Actuarial estimates of freedom from RP (FFRP), in-lobe control (ILC), and overall survival (OS) were calculated with the Kaplan-Meier method and compared between cohorts via the log rank method. Results: At a median follow up of 11.9 months (range 1.2 to 81 months), 3 patients developed grade 2+ RP at a median of 4.0 months (range: 1.0-14.8 months). The crude rates of RP were 6.3% and 2.9% for patients with and without prior ALD, respectively (p>0.05). The 2 year Kaplan-Meier estimates of freedom from RP were 86% and 97% (p>0.05). Crude rates of all grade 2+ pulmonary toxicity were 11.8% and 2.9%, respectively, with associated 2 year estimates of 97% and 81%, respectively (p>0.05). The 2 cohorts were well matched by mean lung dose (4.67 Gy vs 4.15 Gy), lung V20 (5.16% vs 4.35%), mean PTV (30.63 cc vs 36.16 cc), and median prescribed dose (50 Gy vs 54) (p>0.05 for all). Conclusions: Observed rates of pulmonary toxicity were low among patients treated by SBRT after ALR. These data provide reassurances that SBRT can be performed safely for patients with prior ALR when conventional lung DVH constraints are utilized. Author Disclosure: J.T. Hayes: None. A.M. Chen: None. M.E. Daly: None.
3145 Dosimetric Comparison of VMAT-Based Lung SBRT Treatments With and Without a Flattening Filter: An Interinstitutional Study B.W. Maidment III,1 C. Geesey,1 C. Xie,2 J. Chinault,2 R. Best,1 J.M. Larner,1 and K. Wijesooriya1; 1University of Virginia Health System, Charlottesville, VA, 2Mary Washington Hospital, Fredericksburg, VA Purpose/Objective(s): SBRT (stereotactic body radiation therapy) is frequently used for the treatment of medically inoperable early stage nonsmall cell lung cancer. Flattening filter free (FFF) beams for SBRT are
3146 Is Molecular Remission as Detected by 18F-FDG PET/CT and Regression Grade After Neoadjuvant Treatment in the Primary Tumor and the Involved Mediastinal Lymph Nodes a Prognostic Factor in Patients With NSCLC Stage III? N.D. Klass,1 M. Schmuecking,1 S.C. Schaefer,2 E. Fritz,1 R.P. Baum,3 N. Cihoric,1 D. Leiser,1 N. Presselt,4 A. Schmid,5 B. Hoksch,6 K.M. Mueller,7 T.G. Wendt,8 B. Klaeser,9 and R. Bonnet10; 1Department of Radiation Oncology, Inselspital, University of Bern, Bern, Switzerland, 2 Institute of Pathology, University of Bern, Bern, Switzerland, 3Department of Nuclear Medicine, Zentralklinik Bad Berka, Bad Berka, Germany, 4 Department of Thoracic Surgery, Zentralklinik Bad Berka, Bad Berka, Germany, 5Department of Medical Oncology, Inselspital, University of Bern, Bern, Switzerland, 6Department of Thoracic Surgery, Inselspital, University of Bern, Bern, Switzerland, 7Institute of Pathology, University of Muenster, Muenster, Germany, 8Department of Radiation Oncology, University of Jena, Jena, Germany, 9Department of Nuclear Medicine, University of Bern, Bern, Switzerland, 10Department of Pneumology, Zentralklinik Bad Berka, Bad Berka, Germany Purpose/Objective(s): To evaluate the role of molecular remission as detected by 18F-FDG PET/CT and regression grade after neoadjuvant treatment followed by surgical resection of pts with NSCLC stage III.
International Journal of Radiation Oncology Biology Physics
offering an acceptable overlap with expert drawn contours and almost halving the target volumes segmentation time. Author Disclosure: C. Valentini: None. L. Boldrini: None. G. Chiloiro: None. G.C. Mattiucci: None. G. Mantini: None. D. Pasini: None. N. Dinapoli: None. S. Chiesa: None. N. Caria: None. V. Valentini: None.
known to decrease treatment time as compared to treatments with the flattening filter (FF) due to a higher dose rate. FFF beams are also thought to have a sharper penumbra, less collimator scatter, reduced leaf transmission, and reduced head leakage. Due to the addition of low energy bremsstrahlung tail, the number of degrees of freedom allowed in planning is also increased. We performed an inter-institutional dosimetric study of FFF versus FF beams for patients eligible for either RTOG 0915 (20 patients) or RTOG 0813 (10 patients) within established protocol criteria to determine if any statistically significant dosimetric advantages/disadvantages were seen. Materials/Methods: Both FFF and FF SBRT plans were generated for thirty lung cancer patients from two institutions with a mean PTV volume of 55.5 cc (STD 46.1 cc). All patient plans consisted of two to four full or partial arcs with up to 15 couch kicks. Parameters of interest included prescription isodose surface coverage, target dose heterogeneity, high dose spillage (location and volume), low dose spillage (location and volume), lung dose spillage, and critical structure maximum and volumetric dose limits. Results: For conformality criteria, we observed equivalent or higher conformality for FFF plans with both 0915 and 0813 patient cohorts. However, statistically significant results for conformality were observed in the 0915 patient group. Observed percentage reductions (mean, STD, p-value) were: High dose spillage location (0.09%, 0.17%, 0.029), high dose spillage volume (0.98%, 1.67%, 0.016), and low dose spillage volume (2.83%, 3.42%, 0.001). Furthermore, both 0915 and 0813 patient cohorts had statistically significant reductions to the total lung volume receiving doses between 11.6 -20.0 Gy. Observed percentage reductions (mean, STD, p-value) were: 0915-V20 (2.25%, 3.12%, 0.004), 0915-V12.4 (2.1%, 1.8%, 0.001), 0915-V11.6 (2.1%, 1.53%, 0.001), 0813-V20 (3.63%, 2.97%, 0.004), 0813-V13.5 (4.47%, 4.48%, 0.04), and 0813-V12.5 (4.29%, 4.61%, 0.04). As expected, skin dose was higher in the FFF plans for both groups (2.34%, 3.0%, 0.02). Conclusions: Our work represents the first comparison of FFF and FF modes using complete RTOG lung SBRT dosimetric parameters. We demonstrate that in addition to shorter treatment times, there are statistically significant dosimetric advantages to using FFF beams for lung SBRT, namely increased dose conformality and decreased low dose lung spillage. Author Disclosure: B.W. Maidment III: None. C. Geesey: None. C. Xie: None. J. Chinault: None. R. Best: None. J.M. Larner: None. K. Wijesooriya: None.
3144 Risk of Pneumonitis After Stereotactic Body Radiation Therapy for Non-Small Cell Lung Cancer in Patients With Prior Anatomic Resection J.T. Hayes,1 A.M. Chen,2 and M.E. Daly1; 1UC Davis Cancer Center, Sacramento, CA, 2University of California, Los Angeles, Los Angeles, CA Purpose/Objective(s): Stereotactic body radiation therapy (SBRT) has emerged as a standard treatment option for early stage, medically inoperable non-small cell lung cancer (NSCLC). Dosimetric factors including lung volume receiving 20 Gy (V20) >10%and mean lung dose (MLD) >4 Gy are established risk factors for radiation pneumonitis (RP) following SBRT, but limited data evaluate the relative risk of RP in patients undergoing SBRT following prior anatomic lung resection (ALR). This study assessed the incidence of RP and all grade 2+ pulmonary toxicity in patients treated with SBRT for NSCLC following ALR and compare toxicity rates to patients without prior ALR. Materials/Methods: The medical records of 83 consecutive patients with T1-T3 NSCLC treated with 87 courses of SBRT for 93 lung tumors (16 central, 77 peripheral) between January 2007 and September 2013 were reviewed. Sixteen patients with a history of prior ALR were identified, including lobectomy (n Z 12), bilobectomy (n Z 1), and pneumonectomy (n Z 3), with 67 patients without history of prior ALD. The most commonly used fractionation regimen was 50Gy in 5 fractions. Toxicities were graded according to the Common Terminology Criteria for Adverse Events (CTCAE) v.4.0. Rates of grade 2+ RP and any grade 2+ pulmonary toxicity were compared between patients with and without prior ALR. Crude rates of RP and all grade 2+ pulmonary toxicity were compared using Fisher’s exact test. Actuarial estimates of freedom from RP (FFRP), in-lobe control (ILC), and overall survival (OS) were calculated with the Kaplan-Meier method and compared between cohorts via the log rank method. Results: At a median follow up of 11.9 months (range 1.2 to 81 months), 3 patients developed grade 2+ RP at a median of 4.0 months (range: 1.0-14.8 months). The crude rates of RP were 6.3% and 2.9% for patients with and without prior ALD, respectively (p>0.05). The 2 year Kaplan-Meier estimates of freedom from RP were 86% and 97% (p>0.05). Crude rates of all grade 2+ pulmonary toxicity were 11.8% and 2.9%, respectively, with associated 2 year estimates of 97% and 81%, respectively (p>0.05). The 2 cohorts were well matched by mean lung dose (4.67 Gy vs 4.15 Gy), lung V20 (5.16% vs 4.35%), mean PTV (30.63 cc vs 36.16 cc), and median prescribed dose (50 Gy vs 54) (p>0.05 for all). Conclusions: Observed rates of pulmonary toxicity were low among patients treated by SBRT after ALR. These data provide reassurances that SBRT can be performed safely for patients with prior ALR when conventional lung DVH constraints are utilized. Author Disclosure: J.T. Hayes: None. A.M. Chen: None. M.E. Daly: None.
3145 Dosimetric Comparison of VMAT-Based Lung SBRT Treatments With and Without a Flattening Filter: An Interinstitutional Study B.W. Maidment III,1 C. Geesey,1 C. Xie,2 J. Chinault,2 R. Best,1 J.M. Larner,1 and K. Wijesooriya1; 1University of Virginia Health System, Charlottesville, VA, 2Mary Washington Hospital, Fredericksburg, VA Purpose/Objective(s): SBRT (stereotactic body radiation therapy) is frequently used for the treatment of medically inoperable early stage nonsmall cell lung cancer. Flattening filter free (FFF) beams for SBRT are
3146 Is Molecular Remission as Detected by 18F-FDG PET/CT and Regression Grade After Neoadjuvant Treatment in the Primary Tumor and the Involved Mediastinal Lymph Nodes a Prognostic Factor in Patients With NSCLC Stage III? N.D. Klass,1 M. Schmuecking,1 S.C. Schaefer,2 E. Fritz,1 R.P. Baum,3 N. Cihoric,1 D. Leiser,1 N. Presselt,4 A. Schmid,5 B. Hoksch,6 K.M. Mueller,7 T.G. Wendt,8 B. Klaeser,9 and R. Bonnet10; 1Department of Radiation Oncology, Inselspital, University of Bern, Bern, Switzerland, 2 Institute of Pathology, University of Bern, Bern, Switzerland, 3Department of Nuclear Medicine, Zentralklinik Bad Berka, Bad Berka, Germany, 4 Department of Thoracic Surgery, Zentralklinik Bad Berka, Bad Berka, Germany, 5Department of Medical Oncology, Inselspital, University of Bern, Bern, Switzerland, 6Department of Thoracic Surgery, Inselspital, University of Bern, Bern, Switzerland, 7Institute of Pathology, University of Muenster, Muenster, Germany, 8Department of Radiation Oncology, University of Jena, Jena, Germany, 9Department of Nuclear Medicine, University of Bern, Bern, Switzerland, 10Department of Pneumology, Zentralklinik Bad Berka, Bad Berka, Germany Purpose/Objective(s): To evaluate the role of molecular remission as detected by 18F-FDG PET/CT and regression grade after neoadjuvant treatment followed by surgical resection of pts with NSCLC stage III.