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J. Coolen
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MINI 25 - Trials, Radiation and Other (ID 142)
- Event: WCLC 2015
- Type: Mini Oral
- Track: Thymoma, Mesothelioma and Other Thoracic Malignancies
- Presentations: 1
- Moderators:J.M. Clavero, R. Hassan
- Coordinates: 9/08/2015, 16:45 - 18:15, 702+704+706
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MINI25.11 - Optimization of Gross Tumour Volume Definition in Lung-Sparing Volumetric Modulated Arc Therapy for Pleural Mesothelioma (ID 2860)
17:45 - 17:50 | Author(s): J. Coolen
- Abstract
- Presentation
Background:
High dose lung-sparing pleural radiotherapy for malignant pleural mesothelioma (MPM) is difficult. Given the steep dose gradient with volumetric modulated arc therapy (VMAT), 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-IV MPM (6 left-sided and 6 right-sided) were included. CT scans with intravenous (IV) contrast, [18]F-FDG PET/CT scans, MRI scans (post-contrast T1-weighted and T2-weighted) and diffusion-weighted images (DWI) were obtained and downloaded from the institutional database onto a standalone image fusion workstation (MIM Software Inc., Cleveland, OH, USA) for image registration and contouring. CT scans were rigidly co-registered with ~18~FDG-CT-PET, with MRI scans and with DWI scans. Four sets of pleural GTVs were defined: 1) a CT-based GTV (GTV~CT~); 2) a PET/CT-based GTV (GTV~CT+PET/CT~); 3) a T1/T2-weighted MRI-based GTV (GTV~CT+MRI~); 4) a DWI-based GTV (GTV~CT+DWI~). Only the pleural tumor was contoured; mediastinal nodes were excluded. In each of the 4 co-registrations, a “quantitative” and a “qualitative” (visual) evaluation of the volumes were performed. “Quantitative” evaluation was carried out through the coefficient of variation (COV; the ratio between the standard deviation [SD] and the mean: a measure of the dispersion of a distribution) and the Jaccard index (the ratio between the union and the intersection between two volumes: a measure of overlap). “Qualitative” evaluation consisted of a visual identification of any additional tumor site in each of the 4 obtained co-registrations.
Results:
Compared to CT-based GTV definition, PET/CT identified additional tumour sites in 12/16 patients. Compared to either CT or PET/CT, MRI and DWI identified additional tumour sites in 15/16 patients. Additional tumour sites were mainly the parietal pleura, the diaphragm and the chest wall. Mean GTV~CT~, GTV~CT+PET/CT~, GTV~CT+MRI~ and GTV~CT+DWI~ (+SD) were respectively 630.1 mL (+302.81), 640.23 (+302.83), 660.8 (+290.8) and 655.2 mL (+290.7). Mean Jaccard index was lower in MRI-based contours versus all the others.
Conclusion:
To the best of our knowledge, this is the first study showing that the integration of the MRI (T1/T2-weighted) and DWI into the target volume definition in lung-sparing hemi-thoracic VMAT in MPM may allow to improve the accuracy of target delineation and reduce the likelihood of geographical misses.
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P1.08 - Poster Session/ Thymoma, Mesothelioma and Other Thoracic Malignancies (ID 224)
- Event: WCLC 2015
- Type: Poster
- Track: Thymoma, Mesothelioma and Other Thoracic Malignancies
- Presentations: 1
- Moderators:
- Coordinates: 9/07/2015, 09:30 - 17:00, Exhibit Hall (Hall B+C)
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P1.08-006 - Lung Toxicity after Post-Operative Radiotherapy after EPP for Mesothelioma and Pneumonectomy for Non-Small Cell Lung Cancer (ID 2863)
09:30 - 09:30 | Author(s): J. Coolen
- Abstract
Background:
Our hypothesis is that MPM patients treated with post-operative RT after EPP are more prone to develop lung toxicity compared to non-small cell lung cancer (NCSLC) patients treated with post-operative RT after pneumonectomy, since their higher baseline inflammation status.
Methods:
We retrospectively reviewed the records of 39 consecutive patients with MPM who received post-operative RT after extrapleural pneumonectomy (EPP), and of 10 consecutive patients with non-small cell lung cancer who received post-operative RT after pneumonectomy between March 2003 and March 2012 at the University Hospitals of Leuven. For MPM patients, the planning target volume was defined as the entire hemi-thorax, chest wall incisions, drain sites, and involved nodal stations. Prescription dose was 54 Gy in 2-Gy fractions delivered to the planning target volume (PTV). For NSCLC patients, the planning target volume was defined as mediastinal nodal stations according to the pathologic nodal involvement. Prescription dose was 54-66 Gy in 2-Gy fractions delivered to the PTV. Both cohorts received induction systemic chemotherapy before surgery. Primary endpoint was lung toxicity. Dyspnea was graded using the Common Toxicity Criteria (CTC) v. 4.03 and was recorded before RT, 45 days after the completion of RT and every 3 months thereafter until the completion of the follow up. Dosimetric dose-volume parameters (lung V5, lung V20, mean lung dose [MLD], mean heart dose, heart V45) were retrieved for both cohorts. The correlation between the dosimetric parameters and the toxicity (dyspnea score) was investigated.
Results:
In MPM patients, the dyspnea score was 0-1 in 24/39 patients (61.5%), 2 in 11/39 patients (28.2%), 3 in 3/39 patients (7.7%) and 4 in 1/39 patients (2.5%). No grade 5 toxicity was recorded. In NSCLC patients, only grade 0-1 dyspnea was registered (grade 0: 4/10 patients; grade 1: 6/10 patients). Mean MLD was 7.56 Gy (range: 1.60-14.80; SD: 3.65) for the MPM group and 5.96 Gy (range: 3.2-14.5; SD: 3.57) for the NSCLC group. Univariate analysis showed a significant correlation between grade > 2 dyspnea and MLD, lung V5 and lung V20.
Conclusion:
Post-operative radiotherapy after EPP is well-tolerated, with 10% of patients experiencing grade > 3 dyspnea. Strict dose-constraints should be applied when radiotherapy is administered in multimodality treatment.
