- Email: [email protected]
Optimal Definition of Target Volumes in Lung-Sparing Pleural Radiotherapy for Malignant Pleural Mesothelioma (Mpm)
Annals of Oncology 25 (Supplement 4): iv542–iv545, 2014 doi:10.1093/annonc/mdu357.6
thoracic malignancies, other 1562P
OPTIMAL DEFINITION OF TARGET VOLUMES IN LUNG-SPARING PLEURAL RADIOTHERAPY FOR MALIGNANT PLEURAL MESOTHELIOMA (MPM)
Pairwise comparison with the Jaccard Index PAIRWISE COMPARISON
JI
CT vs. CT+CT-PET CT vs. CT+MRI CT vs. CT+PET+MRI CT+CT-PET vs. CT+MRI CT+CT-PET vs. CT+PET+MRI CT+MRI vs. CT+PET+MRI
0.97 0.91 0.91 0.91 0.91 0.99
Mean GTV CT was the smallest volume (655.9+322.1 cc): when compared with CT/PET-based, CT/MRI-based and CT/PET/MRI-based volumes, they were respectively 1.26%, 5.33% and 5.9% larger. COV was lower in MRI-based contours (0.43 vs 0.48-0.49), indicating a lower dispersion of the values. Mean JI ranges from 0.91 and 0.99: a lower concordance was registered between CT/ MRI-based contours versus all the others. “Geographical miss” was identified in 11/12 patients in CT/MRI-based contours and in 4/12 patients in CT/ PET-based volumes.
Conclusions: To the best of our knowledge, this is the first study showing that the integration of MRI into the target volume definition in hemithoracic radiotherapy in MPM may allow to improve the accuracy of target delineation and reduce the likelihood of geographical misses. Disclosure: All authors have declared no conflicts of interest.
abstracts
Aim: High dose lung-sparing pleural radiotherapy for malignant mesothelioma is difficult. Accurate target delineation is critical. The optimal imaging modality to define radiotherapy target volumes has not been studied in depth. This is the aim of the present study. Methods: Twelve consecutive patients with a histopathological diagnosis of stage I-III MPM (6 left-sided and 6 right-sided) were included. CT scans with iv contrast, 18 FDG-CT/PET scans and MRI scans were obtained. CT scans were rigidly co-registered with 18FDG-CT-PET and with MRI scans. Four sets of pleural GTVs were defined: based on CT, on CT/PET, on CT/MRI and on CT/PET/MRI. The pleural tumour was contoured; mediastinal nodes were excluded. “Quantitative” evaluation of the volumesincluded the coefficient of variation [COV, defined as the ratio between the standard deviation and the mean]) and pairwise comparison of the overlap index with the Jaccard index (JI, defined as the ratio of the intersection between two volumes and
Table: 1562P
© European Society for Medical Oncology 2014. Published by Oxford University Press on behalf of the European Society for Medical Oncology. All rights reserved. For permissions, please email: [email protected].
Downloaded from http://annonc.oxfordjournals.org/ by guest on December 31, 2015
A. Botticella1, G. Defraene1, K. Nackaerts2, C. Deroose3, J. Coolen4, P. Nafteux5, S. Peeters1, D. De Ruysscher1 1 Radiation Oncology, University Hospitals Leuven - Campus Gasthuisberg, Leuven, BELGIUM 2 Respiratory Oncology Unit, University Hospital Leuven, Leuven, BELGIUM 3 Nuclear Medicine, University Hospitals Leuven - Campus Gasthuisberg, Leuven, BELGIUM 4 Department of Radiology, University Hospitals Leuven - Campus Gasthuisberg, Leuven, BELGIUM 5 Thoracic Surgery, University Hospitals Leuven - Campus Gasthuisberg, Leuven, BELGIUM
their union). “Qualitative” (visual) assessment of the different volumes was also performed, in order to evaluate the “geographical miss”. Results:
thoracic malignancies, other 1562P
OPTIMAL DEFINITION OF TARGET VOLUMES IN LUNG-SPARING PLEURAL RADIOTHERAPY FOR MALIGNANT PLEURAL MESOTHELIOMA (MPM)
Pairwise comparison with the Jaccard Index PAIRWISE COMPARISON
JI
CT vs. CT+CT-PET CT vs. CT+MRI CT vs. CT+PET+MRI CT+CT-PET vs. CT+MRI CT+CT-PET vs. CT+PET+MRI CT+MRI vs. CT+PET+MRI
0.97 0.91 0.91 0.91 0.91 0.99
Mean GTV CT was the smallest volume (655.9+322.1 cc): when compared with CT/PET-based, CT/MRI-based and CT/PET/MRI-based volumes, they were respectively 1.26%, 5.33% and 5.9% larger. COV was lower in MRI-based contours (0.43 vs 0.48-0.49), indicating a lower dispersion of the values. Mean JI ranges from 0.91 and 0.99: a lower concordance was registered between CT/ MRI-based contours versus all the others. “Geographical miss” was identified in 11/12 patients in CT/MRI-based contours and in 4/12 patients in CT/ PET-based volumes.
Conclusions: To the best of our knowledge, this is the first study showing that the integration of MRI into the target volume definition in hemithoracic radiotherapy in MPM may allow to improve the accuracy of target delineation and reduce the likelihood of geographical misses. Disclosure: All authors have declared no conflicts of interest.
abstracts
Aim: High dose lung-sparing pleural radiotherapy for malignant mesothelioma is difficult. Accurate target delineation is critical. The optimal imaging modality to define radiotherapy target volumes has not been studied in depth. This is the aim of the present study. Methods: Twelve consecutive patients with a histopathological diagnosis of stage I-III MPM (6 left-sided and 6 right-sided) were included. CT scans with iv contrast, 18 FDG-CT/PET scans and MRI scans were obtained. CT scans were rigidly co-registered with 18FDG-CT-PET and with MRI scans. Four sets of pleural GTVs were defined: based on CT, on CT/PET, on CT/MRI and on CT/PET/MRI. The pleural tumour was contoured; mediastinal nodes were excluded. “Quantitative” evaluation of the volumesincluded the coefficient of variation [COV, defined as the ratio between the standard deviation and the mean]) and pairwise comparison of the overlap index with the Jaccard index (JI, defined as the ratio of the intersection between two volumes and
Table: 1562P
© European Society for Medical Oncology 2014. Published by Oxford University Press on behalf of the European Society for Medical Oncology. All rights reserved. For permissions, please email: [email protected].
Downloaded from http://annonc.oxfordjournals.org/ by guest on December 31, 2015
A. Botticella1, G. Defraene1, K. Nackaerts2, C. Deroose3, J. Coolen4, P. Nafteux5, S. Peeters1, D. De Ruysscher1 1 Radiation Oncology, University Hospitals Leuven - Campus Gasthuisberg, Leuven, BELGIUM 2 Respiratory Oncology Unit, University Hospital Leuven, Leuven, BELGIUM 3 Nuclear Medicine, University Hospitals Leuven - Campus Gasthuisberg, Leuven, BELGIUM 4 Department of Radiology, University Hospitals Leuven - Campus Gasthuisberg, Leuven, BELGIUM 5 Thoracic Surgery, University Hospitals Leuven - Campus Gasthuisberg, Leuven, BELGIUM
their union). “Qualitative” (visual) assessment of the different volumes was also performed, in order to evaluate the “geographical miss”. Results: