Treating lung cancer with dynamic conformal arc therapy: a dosimetric study

Primož Peterlin,Karmen Stanič,Ignasi Méndez,Andrej Strojnik

doi:10.1186/s13014-017-0823-y

Primož Peterlin, Karmen Stanič + Show 2 more

Open Access

https://doi.org/10.1186/s13014-017-0823-y

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Journal: Radiation Oncology	Publication Date: Jun 2, 2017
Citations: 8	License type: open-access

Affiliation: Institute of Oncology Ljubljana

Abstract

BackgroundLung cancer patients are often in poor physical condition, and a shorter treatment time would reduce their discomfort. Dynamic conformal arc therapy (DCAT) offers a shorter treatment time than conventional 3D conformal radiotherapy (3D CRT) and is usually available even in departments without inverse planning possibilities. We examined its suitability as a treatment modality for lung cancer patients.MethodsOn a cohort of 35 lung cancer patients, relevant dosimetric parameters were compared in respective DCAT and 3D CRT treatment plans. Radiochromic film dosimetry in an anthropomorphic phantom was used to compare both DCAT and 3D CRT dose distributions against their planned counterparts.ResultsIn comparison with their 3D CRT counterparts, DCAT plans equal or exceed the agreement between the calculated dose and the dose measured using film dosimetry. In dosimetric comparison, DCAT performed significantly better than 3D CRT in dose conformity to PTV and the number of monitor units used per plan, and significantly worse in dose homogeneity, mean lung dose and lung volume exposed to 5 Gy or more (V5Gy). No significant difference was found in the V20Gy value to lung, dose to 1 cm3 of spinal cord, and the mean dose to oesophagus. Improvements in V20Gy and V5Gy were found to be negatively correlated. DCAT plans differ from 3D CRT by exhibiting a moderate negative correlation between target volume sphericity and dose homogeneity.ConclusionsWith respect to the agreement between the planned and the irradiated dose distribution, DCAT appears at least as reliable as 3D CRT. In specific conditions concerning the patient anatomy and treatment prescription, DCAT may yield more favourable dosimetric parameters. On average, however, conventional 3D CRT usually obtains better dosimetric parameters. We can thus only recommend DCAT as a complementary technique to the conventional 3D CRT.

Highlights

Lung cancer patients are often in poor physical condition, and a shorter treatment time would reduce their discomfort
With the dose threshold set to 10% Dmax and using 3% as dose tolerance and 3 mm as positional tolerance, the median value of the points with γ < 1 was 94.8% for conventional 3D conformal radiotherapy (3D CRT) plans, and 97.3% (96.5%, 98.6%) for Dynamic conformal arc therapy (DCAT) plans
Setting dose and positional tolerances to (2%, 2 mm), we obtain for γ < 1 a median of 88.2% (85.1%, 91.3%) for conventional 3D CRT plans and 95.5% (94.5%, 98.6%) for DCAT plans

Summary

Introduction

Lung cancer patients are often in poor physical condition, and a shorter treatment time would reduce their discomfort. In non-small cell lung cancer, curative radiotherapy includes patients with inoperable early stage and radiotherapy combined with concomitant chemotherapy. The concern about the interplay between the MLC and organ motion applies to every form of radiotherapy in which only part of the treatment volume is irradiated at a time. This applies to all forms of intensitymodulated therapy, including advanced techniques such as volumetric modulated arc therapy (VMAT) and tomotherapy, the “field-in-field” technique, or “forwardplanning IMRT” technique, as well as dynamic- or virtual wedges

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