Lung and Heart Dose Variability during Radiotherapy of Non-Small Cell Lung Cancer

Publication date: Available online 8 March 2017
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Nuzhat Jan, Christopher Guy, Leonid B. Reshko, Geoffrey D. Hugo, Elisabeth Weiss
Purpose/ObjectivesThe risk for lung and heart toxicity is typically assessed based on dose parameters during initial treatment planning. This study investigates volume and dose variability during radiotherapy.Material/MethodsIn this longitudinal investigation, variations in lung and heart volumes and standard dose parameters of mean lung dose (MLD), lung V20Gy, mean heart dose (MHD), and heart V40Gy were analyzed on weekly 4D CTs of 15 lung cancer patients during conventionally fractionated radiochemotherapy. Tumor, individual lung lobes and heart were delineated on the mid-ventilation phase of weekly 4D CTs. Lung lobes and heart were contoured also on individual breathing phases of pre-, mid- and post-treatment scans. Planning dose was transferred to consecutive scans via rigid registration. Volume and dose variations were assessed relative to the initial planning scan.ResultsInterfraction lung volume variability relative to week 0 was twice as large as tidal volume variability (8.0% ± 5.3% vs. 4.0% ± 3.3%, p=0.003). Interfraction lung volume variation ranged between 0.8% and 17.1% for individual patient means. Lower lung lobes had larger volume variability compared to upper lobes (13.5% ± 8.1% vs. 7.0% ± 5.0%, p<0.00001). Average MLD variation was 0.5 Gy (range 0.2 Gy to 1.0 Gy for individual patient means) and average lung V20Gy variation 0.9% (range 0.2% to 1.6%). Average heart volume variation was 7.2% (range 3.4% to 12.6%). Average MHD variation was 1.2 Gy (range 0.1 Gy to 3.0 Gy) and average heart V40Gy variation 1.4% (range 0% to 4.2%).ConclusionsAnatomical and positional variations during radiotherapy induce changes in radiation doses to lung and heart. Repeated lung and heart dose assessment will provide a better estimate of the actually delivered dose and will improve prediction models for normal tissue toxicity, if assessed in larger cohorts.

Teaser

The risk for lung and heart toxicity is typically assessed based on dose parameters during initial treatment planning. The present analysis shows that anatomical variations during radiotherapy induce potentially relevant changes in radiation dose to lungs and heart. Repeated lung and heart dose assessment will provide a better estimate of the actually delivered dose.


http://ift.tt/2mXcb4I