An Essential Treatment Pattern of Lung Cancer: Magnetic Resonance-Guided Stereotactic Body Radiotherapy

Abstract

<h3>Purpose/Objective(s)</h3> Stereotactic body radiation therapy (SBRT) has emerged as an important treatment for non-resectable lung cancer. MR-Linac can offer superior soft-tissue contrast, have the ability to visualize cancer physiology and daily on-table treatment adaptation. Obviously combined SBRT with MR-Linac holds the promise to improve the accuracy of radiotherapy and reduce the toxicity of organs-at-risk (OAR). However, data on treatment effect and patient acceptance is still limited. <h3>Materials/Methods</h3> Between July 2019 and October 2021,14 patients with lung cancer were treated with an MRI-Linac guided SBRT, of them, 6 in left upper lobe, 1 in left lower lobe, 2 in right upper lobe and 5 in right lower lobe. The CT simulation used a Siemens big-bore CT scanner (syngo CT VA62A) for all patients. All patients were treated with step and shoot intensity modulated radiotherapy (IMRT). The online plan was created while the patient was on the treatment table and based on the online MRI images; pre-treatment CT was deformably registered to the online MRI to obtain position error. All patients used adapt to position (ATP) workflow. The curative effect and adverse reactions in the process of treatment need to be paid close attention to, and the adverse reactions should be treated and recorded in time. <h3>Results</h3> Fourteen patients (with n=2 metastases; n=12 primary tumor) received MR-guided SBRT. Median prescribed does was 60Gy(range:54Gy-70Gy) and median planning target volume was 28.8cc (range:11.1-93.4cc). Two patients occurred grade I bone marrow suppression and two occurred grade II bone marrow suppression. One patient occurred grade I gastrointestinal toxicity. No patient occurred grade III or higher toxicity. Only one patient developed left lung recurrence and left hilar lymph node metastasis ten months after treatment, one patient was not re-examined, and others were controlled locally. <h3>Conclusion</h3> In summary, MR-guided SBRT of lung cancer is well-effective and well-accepted. The results are promising that it holds with prominent local control and mild adverse events. The influence of magnetic field on dosimetry remains to be studied. The relevant work is also conducted.