1. Radiation Oncology Department, Bank of Cyprus Oncology Center.
VMAT-technique (volumetric modulated arc therapy) VS 3D conformal radiation for 60 patients with Lymphomas,
Radiation Oncology Department, Bank of Cyprus Oncology Center.
Marilena Theodorou, MD 1, , Ali Vehbi Artikan MSc, DABR, 2 Andriana Peratikou, MSc, DABR, 2 , Stefani Stefanou MSc,CSci, MIPEM, 2, , Lora Ioannou, MSc, CSci, MIPEM, 2,, Efthymiou Themos MSc, 2, Erato Stylianou MSc, 2,, Aristotelis Giannos MSc 2, Kyriaki Michailidou, PhD, 4 Demetrios Andreopoulos, MD,PhD 1
1 Radiation Oncology Department, Bank of Cyprus Oncology Center, 2 Medical Physics Department, Bank of Cyprus Oncology Center, 3 Department of electron microscopy/molecular pathology and the Cyprus School of molecular medicine, the Cyprus Institute for Genetics and Neurology
Contact:
Radiation Oncology and Radiodiagnostics, Bank of Cyprus Oncology Center, Nicosia, Cyprus ,
Introduction
From October 2015 to January 2018, 60 patients were irradiated in the Radiation Oncology Department at the Bank of Cyprus Oncology Center due to either Non Hodgkin Lymphoma or Hodgkin Lymphoma. All patients were planned with Monaco TPS using both VMAT (volumetric modulated arc therapy) and 3D conformal techniques. Of these 60 patients, 12 were initially 3D planned and treated, as no VMAT capabilities were available at the time. All patients were treated on Elekta Synergy Linear Accelerators, with Cone-Beam-CT set-up verification. For the purposes of this project, each of these 60 patients had both VMAT and 3D plans generated in order to carry out a comparison of the two modalities, irrespective of the treatment technique administered
Results
From the results of the project, it was seen that the organs at risk like breasts, larynx, lungs as well as spinal cord, are better spared when using VMAT compared to 3D conformal. In addition, the coverage of the PTVs achieved, was higher in the VMAT plans when compared to the 3D conformal plans. After comparison of individual patient plans, it was noted that the VMAT plans delivered higher coverage to the targets and were able to better spare the organs at risk in the vicinity of the target. The radiation tolerance was good without significant side effects or complications being observed. Some acute side effects such as skin erythema, mild dyscataposia, mild esophagitis, were mentioned. No late side effects were mentioned in further follow ups (FU). .
Methods
Before the planning CT is carried out locally, every patient has a post chemo restaging CT scan, in some cases this is in conjunction with an FDG PET scan. If the Lymphoma was located at the cervical/mediastinal region, a fixation thermoplastic mask was used. The contouring of the Clinical targets, as defined by ICRU (GTV, CTV, and PTV) and the organs at risk (OAR) was carried out with Oncentra MasterPlan and treatment planning was carried out using the Monaco Treatment Planning System. For an accurate clinical target definition, the pre-Chemotherapy-CT, post-Chemotherapy-CT, FDG-PET and MRI, if available, were fused with the Planning-CT. The GTV (gross tumor volume) included the macroscopically remaining Lymphoma in the post-Chemotherapy-CT-scan. The CTV (clinical tumor volume) included the involved lymph-node stations in the pre-Chemotherapy-CT-scan and the PTV included the GTV+CTV adapted for anatomical structures. For each of the patients having VMAT treatment, patient specific QA was carried out prior to the start of their treatment. B
Tab.2. Statistically analysis for the PTV coverage (95%) for 3D conformal plans and VMAT plans for all the 60 patients. 3D Mean= 96.8 % SD =2.69 , VMAT Mean= SD=0.95
Tab.1 : 3D Vs VMAT, statistical analysis for the spinal cord as an OAR for the 60 patients. The most significant difference appears to be the lower mean dose absorbed by the spinal cord for the VMAT technique. 3D Mean = 29, SD (standard deviation) =12.2 VMAT Mean =24, SD=9.4. The difference using Wilcoxon rank sum test for paired values gives a p-value = 1.9 x10 -5
Conclusion and summary
In conclusion therefore, we suggest that VMAT techniques can be implemented for Radiotherapy. of Lymphomas due to the superiority of this technique when compared to 3D conformal methods, both in coverage of the PTV and the sparing of the organs at risk, such as spinal cord, breasts and lungs
DEGRO 2018, Leipzig
Image 1: old patient with mediastinal Non Hodgkin’s Lymphoma after 6 cycles R-CHOP with partial response, planned with VMAT technique (top plan) and 3D conformal technique (bottom plan). The DVH (top right) shows the better organ sparing for the spinal cord, lungs and breasts for the VMAT plan.