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Assessing Inter- and Intrafraction Liver Motion During Radiation Therapy in Patients With Obesity or Ascites
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Volume 99 Number 2S Supplement 2017 did not significantly correlate with PFS or OS. 6-month post-treatment SUVmax and SUVpeak correlated with both OS and PFS (all HR 1.2, p0.005). 100% of treatment failures were detectable by the combination of clinical exam and PET/CT; however, when used in isolation, clinical exam, PET/CT, or CT failed to detect some recurrences. The 3and 6-month post-treatment PET/CT in isolation detected 3 and 5 unique recurrences, respectively. Conclusion: Although pre-treatment PET/CT increased detection of nodal metastases, metabolic tumour characteristics did not predict survival outcomes in ACC following radical CRT. Post-treatment, the combination of clinical exam and PET/CT effectively detected all treatment failures; however the optimal timing of post-treatment PET/CT imaging remains unclear. Author Disclosure: A. Duimering: None. T. Riauka: None. A. McEwan: None. S. Ghosh: None. Y. Nijjar: None. J. Jacobs: None. R. Reif: None. T. Nijjar: None. D.M. Severin: None. K. Tankel: None. N.H. Usmani: None. A.M. Fairchild: Independent Contractor; Alberta Health Services. R. MacEwan: None. E. Hudson: None. C. Wong: None. D. Schiller: None. K. Mulder: None. C.M. Doll: None. K. Joseph: None.
2349 Assessing Inter- and Intrafraction Liver Motion During Radiation Therapy in Patients With Obesity or Ascites S.W. Dutta, J.N. Tehrani, H. Nourzadeh, B.D. Camarata, E.M. Janowski, and K. Wijesooriya; Department of Radiation Oncology, University of Virginia, Charlottesville, VA Purpose/Objective(s): Limited data exists evaluating set-up reproducibility in obese patients treated with intensity modulated, volumetric modulated arc, or stereotactic radiotherapy to liver tumors. For liver tumors treated at our institution, deep inspiratory breath hold (DIBH) during radiation treatments is utilized for motion management. Cone beam computed tomography (CBCT) scans are performed before and, if needed, during each fraction to ensure proper alignment. The purpose of this study is to quantify the liver motion with DIBH compared to free breathing (FB) at CT simulation and to assess reproducibility of liver position on DIBH CBCTs across the patient’s radiation treatment course with respect to the planning DIBH CT. How these errors give rise to dosimetric uncertainties were also quantified. Materials/Methods: Patients treated with DIBH were selected for analysis, and clinical characteristics were collected, including body mass index (BMI). The liver was contoured on the FB simulation CT, DIBH simulation CT, and DIBH CBCT datasets. Mean liver motion in all directions, with standard deviation (SD) and confidence interval (CI), was calculated using the Velocity system (Varian Medical Systems) after rigidly registering the planning CT dataset to each CBCT dataset by bony anatomy. The robustness analysis of important ROIs was performed using in-house GPU-accelerated software. The software simulated 1000 different virtual treatments each sampled from uncertainty model governing daily patient variations. Results: Six patients treated from October 2016 to December 2016 were analyzed. Mean BMI was 34.3 kg/m2 (range 31.6-35.5 kg/m2). Four patients were severely obese, and two patients were moderately obese, according to WHO BMI classification. Mean liver shift from FB to DIBH in the superior/inferior direction was 32.1 mm (range 25.245.7 mm) and 16.8 mm (range 9.7-22.0 mm) anteriorly/posteriorly. A total of 36 DIBH CBCT datasets were obtained prior to treatment, during treatment, and at the end of treatment. The mean of the absolute value of liver shift between daily CBCT acquisitions and planning DIBH CT was 2.6 mm (SD 1.7 mm) in the anterior/posterior direction, 3.5 mm laterally (SD 1.8 mm), and 4.4 mm (SD 1.9 mm) superiorly/ inferiorly. Two out of six patients received paracenteses prior to
simulation and each fraction. The mean 3-D vector-based deviations for the patients who received paracenteses for ascites was 2.3 mm (95% CI: 0.7-3.9 mm) and 1.6 mm (95% CI: 0.7-2.5 mm) for those who did not. Esophagus, liver, heart, stomach, and spinal cord ranked from highest to lowest in terms of the variance of dosimetric indices within 95th confidence interval. Conclusion: DIBH is an effective technique in minimizing intra-fraction liver motion in obese patients, and minimal inter- and intra-fraction variability is seen in these patients when daily CBCT imaging is utilized for alignment. Pre-treatment paracenteses followed by CBCT may minimize inter-treatment variation in patients with ascites. Author Disclosure: S.W. Dutta: None. J.N. Tehrani: None. H. Nourzadeh: None. B.D. Camarata: None. E. Janowski: None. K. Wijesooriya: None.
2350 Surgical Resection of Clinical Lymph Node Positive Esophageal Cancer after Chemoradiotherapy: A National Cancer Database Analysis G. Eastwick, D. Wang, and J.A. Bogart; SUNY Upstate Medical University, Syracuse, NY Purpose/Objective(s): Though surgical resection (SR) is the mainstay of treatment for early stage esophageal cancer and impacts local tumor control, prospective trials have not demonstrated an overall survival (OS) benefit for SR after combined chemotherapy and radiotherapy (ChRT) in locally advanced disease. We hypothesized that the impact of SR on OS may thus be limited in patients with clinical lymph node positive (CN+) esophageal cancer in the setting of ChRT. Materials/Methods: The National Cancer Database (NCDB) was queried for patients diagnosed with clinical or pathologic lymph node positive nonmetastatic esophageal cancer from 2004-2014. Patient demographics, tumor characteristics, treatment parameters, and survival outcomes were analyzed. Kaplan-Meier methods and multivariate Cox models were used to compare survivals for statistical analysis. Results: Overall, 18,251 patients had CN+ disease. Mean age was 67 years; 75% were male. The majority were adenocarcinoma with onethird squamous cell carcinoma. Both median OS and 5-yr OS were higher with ChRT plus SR (nZ1,338) compared with ChRT alone (nZ8,403); 33.8 months and 37.9% versus 13 months and 14.4%, respectively. On multivariate analysis including facility type, age, gender, race, grade, histology, and performance status, the hazard ratio for death was 0.43 (95% confidence interval: 0.42 e 0.44) in favor of the ChRT plus SR group. The cohort (nZ13,763) of patients with pathologic lymph nodes (PN+) that were clinically negative (CN-) was used for comparison. In the population treated with ChRT alone, CN+ patients had worse 5-year OS compared with CN- patients (14.4% versus 17.2%). However, 5-yr OS in was similar for CN+ and CNpatients treated with ChRT plus SR (37.9% versus 34.7%). The hazard ratio for death is 0.56 (95% CI 0.54 e 0.58) for CN-, PN+ disease in favor of ChRT plus SR. Conclusion: Long-term survival is a possibility in patients with clinical lymph node positive esophageal cancer. This NCDB analysis shows better OS with ChRT plus SR compared with ChRT alone, although this observation is limited by patient selection bias. The benefit of SR after ChRT appears as least as great in CN+ esophageal cancer compared to those with only pathologically involved lymph nodes. These data suggest SR should be strongly considered in appropriate patients with clinical lymph node positive esophageal cancer. Author Disclosure: G. Eastwick: None. D. Wang: None. J.A. Bogart: Partner; Upstate University Radiation Oncology. Travel Expenses; Alliance Clinical Trials. Chair, radiation oncology committee; Alliance.
Volume 99 Number 2S Supplement 2017 did not significantly correlate with PFS or OS. 6-month post-treatment SUVmax and SUVpeak correlated with both OS and PFS (all HR 1.2, p0.005). 100% of treatment failures were detectable by the combination of clinical exam and PET/CT; however, when used in isolation, clinical exam, PET/CT, or CT failed to detect some recurrences. The 3and 6-month post-treatment PET/CT in isolation detected 3 and 5 unique recurrences, respectively. Conclusion: Although pre-treatment PET/CT increased detection of nodal metastases, metabolic tumour characteristics did not predict survival outcomes in ACC following radical CRT. Post-treatment, the combination of clinical exam and PET/CT effectively detected all treatment failures; however the optimal timing of post-treatment PET/CT imaging remains unclear. Author Disclosure: A. Duimering: None. T. Riauka: None. A. McEwan: None. S. Ghosh: None. Y. Nijjar: None. J. Jacobs: None. R. Reif: None. T. Nijjar: None. D.M. Severin: None. K. Tankel: None. N.H. Usmani: None. A.M. Fairchild: Independent Contractor; Alberta Health Services. R. MacEwan: None. E. Hudson: None. C. Wong: None. D. Schiller: None. K. Mulder: None. C.M. Doll: None. K. Joseph: None.
2349 Assessing Inter- and Intrafraction Liver Motion During Radiation Therapy in Patients With Obesity or Ascites S.W. Dutta, J.N. Tehrani, H. Nourzadeh, B.D. Camarata, E.M. Janowski, and K. Wijesooriya; Department of Radiation Oncology, University of Virginia, Charlottesville, VA Purpose/Objective(s): Limited data exists evaluating set-up reproducibility in obese patients treated with intensity modulated, volumetric modulated arc, or stereotactic radiotherapy to liver tumors. For liver tumors treated at our institution, deep inspiratory breath hold (DIBH) during radiation treatments is utilized for motion management. Cone beam computed tomography (CBCT) scans are performed before and, if needed, during each fraction to ensure proper alignment. The purpose of this study is to quantify the liver motion with DIBH compared to free breathing (FB) at CT simulation and to assess reproducibility of liver position on DIBH CBCTs across the patient’s radiation treatment course with respect to the planning DIBH CT. How these errors give rise to dosimetric uncertainties were also quantified. Materials/Methods: Patients treated with DIBH were selected for analysis, and clinical characteristics were collected, including body mass index (BMI). The liver was contoured on the FB simulation CT, DIBH simulation CT, and DIBH CBCT datasets. Mean liver motion in all directions, with standard deviation (SD) and confidence interval (CI), was calculated using the Velocity system (Varian Medical Systems) after rigidly registering the planning CT dataset to each CBCT dataset by bony anatomy. The robustness analysis of important ROIs was performed using in-house GPU-accelerated software. The software simulated 1000 different virtual treatments each sampled from uncertainty model governing daily patient variations. Results: Six patients treated from October 2016 to December 2016 were analyzed. Mean BMI was 34.3 kg/m2 (range 31.6-35.5 kg/m2). Four patients were severely obese, and two patients were moderately obese, according to WHO BMI classification. Mean liver shift from FB to DIBH in the superior/inferior direction was 32.1 mm (range 25.245.7 mm) and 16.8 mm (range 9.7-22.0 mm) anteriorly/posteriorly. A total of 36 DIBH CBCT datasets were obtained prior to treatment, during treatment, and at the end of treatment. The mean of the absolute value of liver shift between daily CBCT acquisitions and planning DIBH CT was 2.6 mm (SD 1.7 mm) in the anterior/posterior direction, 3.5 mm laterally (SD 1.8 mm), and 4.4 mm (SD 1.9 mm) superiorly/ inferiorly. Two out of six patients received paracenteses prior to
simulation and each fraction. The mean 3-D vector-based deviations for the patients who received paracenteses for ascites was 2.3 mm (95% CI: 0.7-3.9 mm) and 1.6 mm (95% CI: 0.7-2.5 mm) for those who did not. Esophagus, liver, heart, stomach, and spinal cord ranked from highest to lowest in terms of the variance of dosimetric indices within 95th confidence interval. Conclusion: DIBH is an effective technique in minimizing intra-fraction liver motion in obese patients, and minimal inter- and intra-fraction variability is seen in these patients when daily CBCT imaging is utilized for alignment. Pre-treatment paracenteses followed by CBCT may minimize inter-treatment variation in patients with ascites. Author Disclosure: S.W. Dutta: None. J.N. Tehrani: None. H. Nourzadeh: None. B.D. Camarata: None. E. Janowski: None. K. Wijesooriya: None.
2350 Surgical Resection of Clinical Lymph Node Positive Esophageal Cancer after Chemoradiotherapy: A National Cancer Database Analysis G. Eastwick, D. Wang, and J.A. Bogart; SUNY Upstate Medical University, Syracuse, NY Purpose/Objective(s): Though surgical resection (SR) is the mainstay of treatment for early stage esophageal cancer and impacts local tumor control, prospective trials have not demonstrated an overall survival (OS) benefit for SR after combined chemotherapy and radiotherapy (ChRT) in locally advanced disease. We hypothesized that the impact of SR on OS may thus be limited in patients with clinical lymph node positive (CN+) esophageal cancer in the setting of ChRT. Materials/Methods: The National Cancer Database (NCDB) was queried for patients diagnosed with clinical or pathologic lymph node positive nonmetastatic esophageal cancer from 2004-2014. Patient demographics, tumor characteristics, treatment parameters, and survival outcomes were analyzed. Kaplan-Meier methods and multivariate Cox models were used to compare survivals for statistical analysis. Results: Overall, 18,251 patients had CN+ disease. Mean age was 67 years; 75% were male. The majority were adenocarcinoma with onethird squamous cell carcinoma. Both median OS and 5-yr OS were higher with ChRT plus SR (nZ1,338) compared with ChRT alone (nZ8,403); 33.8 months and 37.9% versus 13 months and 14.4%, respectively. On multivariate analysis including facility type, age, gender, race, grade, histology, and performance status, the hazard ratio for death was 0.43 (95% confidence interval: 0.42 e 0.44) in favor of the ChRT plus SR group. The cohort (nZ13,763) of patients with pathologic lymph nodes (PN+) that were clinically negative (CN-) was used for comparison. In the population treated with ChRT alone, CN+ patients had worse 5-year OS compared with CN- patients (14.4% versus 17.2%). However, 5-yr OS in was similar for CN+ and CNpatients treated with ChRT plus SR (37.9% versus 34.7%). The hazard ratio for death is 0.56 (95% CI 0.54 e 0.58) for CN-, PN+ disease in favor of ChRT plus SR. Conclusion: Long-term survival is a possibility in patients with clinical lymph node positive esophageal cancer. This NCDB analysis shows better OS with ChRT plus SR compared with ChRT alone, although this observation is limited by patient selection bias. The benefit of SR after ChRT appears as least as great in CN+ esophageal cancer compared to those with only pathologically involved lymph nodes. These data suggest SR should be strongly considered in appropriate patients with clinical lymph node positive esophageal cancer. Author Disclosure: G. Eastwick: None. D. Wang: None. J.A. Bogart: Partner; Upstate University Radiation Oncology. Travel Expenses; Alliance Clinical Trials. Chair, radiation oncology committee; Alliance.