DE-CT in Lung Cancer Proton Therapy (DE-CT)
|Study Design:||Intervention Model: Single Group Assignment
Masking: No masking
Primary Purpose: Other
|Official Title:||DE-CT vs. SE-CT as Optimal Imaging During Treatment for Adaptive Proton Therapy in Stage III Non Small Cell Lung Cancer (NSCLC)|
- Dose distribution on the CTV (measured in Gy) [ Time Frame: Measured during 2nd and 4th week of radiation treatment ]Dose distribution on the CTV (clinical target volume) of the tumour and the lymph nodes of DE-CT vs. SE-CT
- Dose distribution on the OAR (measured in Gy) [ Time Frame: Measured during 2nd and 4th week of radiation treatment ]Dose distribution on the OAR (organs at risk), lungs, heart, aorta, pulmonary artery, superior vena cava, oesophagus, spinal cord, vertebral body, of DE-CT vs. SE-CT
|Study Start Date:||September 2016|
|Estimated Study Completion Date:||December 2017|
|Estimated Primary Completion Date:||September 2017 (Final data collection date for primary outcome measure)|
Patients included in the trial will receive DE-CT in stead of SE-CT's.
Procedure: DE-CT's and SE-CT
Patients included in the trial will receive 3 extra DE-CT's and 3 extra SE-CT's
In order to calculate the dose distribution of protons adequately, accurate estimations of the stopping power ratio (SPR) medium to water, are required. Using a conversion from single energy CT (SE-CT) images results in an uncertainty in the SPR of at least 3-4%. This uncertainty results in in the use of larger margins around the clinical target volume (CTV) and hence more dose to the organs at risk (OAR). It also effects in the conservative use of beam directions, which are often sub-optimal, to avoid irradiating normal tissues.
Dual energy CT (DE-CT) improves the accuracy of the SPR and therefore the proton range estimation.
An evaluation of the proton range for several tissues using SE-CT and DE-CT as input to Monte Carlo (MC) simulations showed on average improvements in range prediction from 0.1% to 2.1% when using DECT instead of SECT, but in several phantoms and also versus proton-CT, the errors on SE-CT based proton stopping power ratios are reported to be more than 7 %.
A limitation of these studies is that most of them were performed in phantoms. In the first clinical data set on five patients with base of skull tumours, it was reported that although the SPR estimation was indeed better for DE-CT than for SE-CT, its clinical relevance was unclear. However, in the same study, phantom measurements showed a large uncertainty of the SPR in the lung. This is due to the large heterogeneity of the lungs and the huge difference in the density of the lungs compared to the mediastinum, the tumour and the chest cavity.
It is therefore important to study the SPR differences of SE-CT compared to DE-CT in lung cancer patients and the impact on the dose distribution especially in the context of adaptive radiotherapy. As during the course of concurrent chemotherapy and radiotherapy, which is the standard treatment in the majority of stage III lung cancer patients, important anatomical changes may occur, it is also of clinical relevance to determine the influence of repeated dose calculations on DE-CT.
Please refer to this study by its ClinicalTrials.gov identifier: NCT02844140
|Maastricht, Limburg, Netherlands, 6229 ET|
|Principal Investigator:||Dirk De Ruysscher, MD, PhD||Maastro Clinic, The Netherlands|