PhD student, MD Thomas Leth Fink Department of Oncology, Vejle Hospital
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OPEN undersøgelse/kliniske data
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A feasibility study on robust optimization in the planning of stereotactic body radiation therapy of lung cancer
In this study we will include 40 patients planned for stereotactic body radiation therapy (SBRT) of a tumor in the lung and make an extra radiation treatment plan using the robust optimization technique for later comparison. We will evaluate whether this technique can reduce the radiation to the normal lung tissue. We will also perform intrafractional XVI imaging during each of the patients 3 treatment fractions, and evaluate actual tumor motion.
Traditional radiation treatment with photons is planned according to the International Commission on Radiation Units and Measurements (ICRU) definitions, including Gross Tumor Volume (GTV), Clinical Target Volume (CTV) and Planning Target Volume (PTV) along with defined normal tissue named Organs At Risk (OAR) and Planning Risk Volume (PRV).
More recent radiation types such as proton radiation have a different dose distribution in the tissue delivering the main part of the radiation in the so-called Bragg Peak, whereas traditional photon radiation delivers the dose all the way through the patient. Proton radiation therefore uses a different approach to the treatment planning through the concept of robust optimization enabled by treatment planning software such as RayStation®, which is used at the Department of Oncology, Vejle Hospital.
It is not known whether the use of robust optimization in the planning of traditional photon radiation can reduce treatment margins and hence also the amount of radiation delivered to the surrounding healthy tissue.
During radiation treatment, a tumor will move with the breathing motion of the patient, some more than others. Tumors in the lower part of the lung will move quite a bit; a study showed a mean movement in the inferior-superior axis of 11.3 millimeters (mm) for tumors in the lower lobe of the lung, with a maximum movement of 53 mm. On this basis we hypothesize that clinically relevant reduction of treatment margins (i.e. size of PTV) is obtainable by using robust optimization.
The aim is to test whether radiation treatment planning using robust optimization can reduce the dose to the normal tissue compared to the usual PTV-margin approach and to use intrafraction imaging to ensure coverage of the tumor.
Description of the cohort
All patients referred to SBRT in 3 fractions at Vejle Hospital for a tumor in the lung can be included.
Data and biological material
Comparison of the normal and robust treatment plans regarding coverage of PTV and GTV, dose to OAR's and PRV's and differences in DVH's. Evaluation of the tumor motion and variations in motion between patients and fractions.
Demographic and tumor related data will be drawn from the electronic patient chart (EPJ-SYD) and the electronic radiation therapy management systems (MOSAIQ and RayStation).