Real-time magnetic resonance imaging guided accelerator in stereotactic body radiation therapy for non-small cell lung cancer.

BACKGROUND

Stereotactic body radiotherapy (SBRT) is crucial for lung tumor treatment, but facing challenges like intra-fractional anatomical changes and organ risks. Magnetic resonance-guided online adaptive SBRT (MRg-SBRT) is an innovative technique promising safer delivery of ablative doses and protect organ at risk (OAR). This study aimed to investigate the feasibility of the whole process of MRg-SBRT for non-small cell lung cancer (NSCLC) patients.

METHODS

Physical parameters of radiotherapy for 23 cases of NSCLC who underwent MRg-SBRT were retrospectively analyzed. This included patients' treatment course, planned target volume (PTV), target area coverage, and OAR recipient volume. The focus was on inter- and intra-fraction MR real-time monitoring to correct off-target. Local control and adverse event outcomes of patients' SBRT treatment were also retrospectively analyzed.

RESULTS

All 23 patients completed treatment on time without any treatment interruptions or pauses due to the MR. Tumor movement was predominantly in the superior-inferior (SI) directions through Elekta Unity real-time online monitoring. The baseline plan was altered in four patients, and an adaptive plan was used to correct inter- and intra-fraction off-targeting in a timely manner. The prescribed dose coverage for PTV was 95.3%, with a median bilateral lung volume 20 (V20) GY of 6.3%, and a maximal dose to the spinal cord of 117.3 cGy. The response results showed that the disease control rate (DCR) was 100% with an objective response rate (ORR) of 82.6%. Follow-up results showed an acute grade one to two pneumonia incidence of 82.6% and grade three pneumonias in one patient.

CONCLUSIONS

MRg-SBRT can guide treatment plans for the clinical needs of SBRT for lung cancer patients, especially for old patients, proving the feasibility of SBRT for lung lesions with MRg-SBRT, and online real-time monitoring reduces intra- and inter-fraction off-targeting, and guarantees the treatment efficiency of patients without significantly increasing the incidence of serious adverse events.