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ORAL 36 - Translational Science/Radiation (ID 151)
- Event: WCLC 2015
- Type: Oral Session
- Track: Treatment of Locoregional Disease – NSCLC
- Presentations: 1
ORAL36.07 - Results of a National Test Run of Treatment Plans for the Standard Arm of a Dose Escalation Trial for Locally Advanced NSCLC (ID 1766)
16:45 - 18:15 | Author(s): W. Ottoson
A national quality assurance program was conducted in order to compare standard radiation treatment plans for locally advanced non-small cell lung cancer (NSCLC) patients in Denmark.
The five participating centres represented 71% of all radiotherapy centres in Denmark. They were provided with the CT images and delineations of GTV, CTV, PTV and organs at risks for five different NSCLC patients. Each centre created treatment plans based on the following optimization objectives: required dose distribution for target coverage 95%-107% of the prescribed dose of 66Gy/33fr to at least 95% of the PTV volume (90% for volume located in lung tissue); constraints for organs at risks D(max) < 50Gy to the spinal cord, D(max) < 70Gy to the oesophagus, V50 < 20% to the heart, V20 < 35% and D(mean) < 20Gy for the total lung volume (excluding the GTV). The treatment planning was done in accordance with the local centre practice; i.e. choice of IMRT versus VMAT, coplanar vs. non-coplanar technique, feasible functionalities for treatment planning optimisation (mean value versus different points at the DVH curve), and any additional local dose constraints (e.g. D(max) < 45Gy to spinal cord and/or V5 < 60% to the total lung volume). Finally, all treatment plans were collected and analysed cooperatively.
All objectives for target coverage and organs at risk were met. There was a wide variability in the dose volume histograms (DVHs) for some of the organs at risk, especially the lungs. This is illustrated in the figure, where the lung DVH from seven different treatment plans, created for the same patient by the five participating centres, is shown. The lung DVHs are overlapping around 20Gy, as all centres had a dose constraint on V20. Some centres had an additional local dose constraint on V5, which resulted in decreased doses to the lungs and increased doses to the mediastinal structures compared with centres that had no dose constraints on V5 for the lungs. Figure 1
Differences in the dose distribution to the organs at risk can have an impact on treatment morbidity (e.g. pneumonitis, oesophagitis). These differences were seen for standard treatment plans, which are often used in multicentre clinical trials as the baseline compared to an experimental arm, where such differences can be even more pronounced. It is highly recommended to perform test runs across centres prior to entering clinical trials in order to uncover differences as the ones presented.
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