Abstract
Background and PurposeThis article retrospectively characterized the geometric and dosimetric changes in target and normal tissues during radiotherapy for lung cancer patients with atelectasis.Materials and MethodsA total of 270 cone beam computed tomography (CBCT) scans of 18 lung patients with atelectasis were collected. The degree and time of resolution or expansion of the atelectasis were recorded. The geometric, dosimetric, and biological changes in the target and lung tissue were also quantified.ResultsThere were two patients with expansion, four patients with complete regression, six patients with partial regression, and six patients with no change. The time of resolution or expansion varied. The tumor volume increased by 3.8% in the first seven fractions, then decreased from the 9th fraction, and by 33.4% at the last CBCT. In the LR direction, the average center of mass (COM), boundaries of the tumors gradually shifted mediastinally. In the AP direction, the COM of the tumors was shifted slightly in the posterior direction and then gradually shifted to the anterior direction; the boundaries of the tumors all moved mediastinally. In the SI direction, the COM of the tumors on the right side of the body was substantially shifted toward the head direction. The boundaries of the tumors varied greatly. D2, D98, Dmean, V95, V107, and TCP of the PTV were reduced during radiotherapy and were reduced to their lowest values during the last two fractions. The volume of the ipsilateral lung tended to increase gradually. The V5, V10, V20, V30, V40, and NTCP of the total lung gradually increased with the fraction.ConclusionsFor most patients, regression of the atelectasis occurred, and the volume of the ipsilateral lung tended to increase while the tumor volume decreased, and the COM and boundary of the tumors shifted toward mediastinum, which caused an insufficient dose to the target and an overdose to the lungs. Regression or expansion may occur for any fraction, and it is therefore recommended that CBCT be performed at least every other day.
Highlights
Lung cancer is one of the most common malignant cancers, with high rates of morbidity and mortality around the world, and non-small cell lung cancer makes up the majority of lung cancer cases [1, 2]
The results showed that the resolution or expansion of atelectasis may occur during any fraction of radiotherapy
This paper focused on the geometric and dosimetric changes in the target and lung tissue in patients with atelectasis during radiotherapy
Summary
Lung cancer is one of the most common malignant cancers, with high rates of morbidity and mortality around the world, and non-small cell lung cancer makes up the majority of lung cancer cases [1, 2]. Some studies have indicated a 10–40% incidence of atelectasis being present at the beginning of lung cancer radiotherapy treatment [3,4,5,6,7]. Atelectasis often occurs in central lung cancer [8,9,10]. The dose to the target volume and the normal tissue are altered, so the introduction of image-guided radiotherapy technology is very important for lung cancer patients with atelectasis [16, 17]. This article retrospectively characterized the geometric and dosimetric changes in target and normal tissues during radiotherapy for lung cancer patients with atelectasis
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