Choice of immobilization of stereotactic body radiotherapy in lung tumor patient by BMI

Abstract

Background An accurate, reproducible, and comfortable immobilization device is essential for stereotactic radiotherapy (SBRT) in patients with lung cancer. This study compared thermoplastic masks (TMP) and vacuum cushion (VCS) system to assess the differences in interfraction and intrafraction setup accuracy and the impact of body mass index (BMI) with respect to the immobilization choice. Methods This retrospective study was conducted on patients treated with lung SBRT between 2012 and 2015 at the Zhejiang cancer hospital. The treatment setup accuracy was analyzed in 121 patients. A total of 687 cone beam computed tomography (CBCT) scans before treatment and 126 scans after treatment were recorded to determine the uncertainties, and plan target volume margins. Data were further stratified and analyzed by immobilization methods and patients’ BMI. The t-test (Welch) was used to assess the differences between the two immobilization systems when stratified by the patients’ BMI. Results For patients with BMI ≥ 24, the mean displacements for the TMP and VCS systems were 1.4 ± 1.2 vs. 2.4 ± 2.0 mm at medial-lateral (ML) direction ( p < 0.001); 2.0 ± 1.9 vs. 2.0 ± 1.9 mm at cranial-caudal (CC) direction ( p = 0.917); and 2.4 ± 1.4 vs. 2.6 ± 2.1 mm at anterior-posterior (AP) direction, ( p = 0.546). The rate of acceptable errors increased dramatically when immobilized by TMP. In the case of patients with BMI < 24, the mean displacements for the TMP and VCS systems were 1.8 ± 1.4 vs. 2.1 ± 1.8 mm at ML direction ( p = 0.098); 2.9 ± 2.3 vs. 2.2 ± 2.2 mm at CC direction ( p = 0.001); and 1.8 ± 1.8 vs. 2.3 ± 2.0 mm at CC direction, ( p = 0.006). The proportion of acceptable errors increased after immobilization by VCS. No difference was detected in the intrafraction setup error by different immobilization methods. Conclusions The immobilization choice of SBRT for lung tumors depends on the BMI of the patients. For patients with BMI ≥ 24, TMP offers a better reproducibility with significantly less interfractional setup displacement than VCS, resulting in fewer CBCT scans. However, VCS may be preferred over TMP for the patients with BMI < 24. Therefore, an optimal immobilization system needs to be considered in different BMI groups for lung SBRT.

Stereotactic body radiotherapy for elderly patients (≥ 75 years) with early-stage non-small cell lung cancer

“…Before treatment, pathological diagnosis was performed by conducting a centesis biopsy of the lung tumor under the guidance of CT. Then, histopathology was confirmed by the pathology department. The SBRT procedure has been described in detail in our previous studies (Chen et al 2019;Dong et al 2019a). Briefly, free breathing 4D-CT was first performed.…”

Comparison of the outcomes of stereotactic body radiotherapy versus surgical treatment for elderly (≥70) patients with early-stage non-small cell lung cancer after propensity score matching

“…Inoperable patients – according to the thoracic surgeon – and those who refused surgical resection were selected for SBRT. The whole process of SBRT has been described previously in detail in our previous study [16, 17]. The gross tumor volume (GTV) included only the primary tumor; the internal target volume (ITV) was determined using CT with a four-dimension CT technique, and the tumor motion was assessed.…”

Video-Assisted Thoracoscopic Lobectomy Versus Stereotactic Body Radiotherapy Treatment for Early-Stage Non-Small Cell Lung Cancer: A Propensity Score-Matching Analysis

“…Inoperable patients, according to the thoracic surgeon, and those who refused surgical resection were selected for SBRT. The whole course of SBRT was reported in our previous study (18)(19)(20). The gross tumor volume (GTV) included only the primary tumor; the internal target volume (ITV) was determined using CT with a four-dimension CT technique, and the tumor motion was assessed.…”