Fixation rate of fiducial gold markers in each segmental bronchus for stereotactic body radiotherapy.

BACKGROUND

In real-time tumor-tracking radiotherapy for lung tumors, placement of fiducials, such as a gold marker (GM), is necessary. However, transbronchially placed GMs often drop out spontaneously. Therefore, we aimed to clarify the fixation rate of GMs in each segmental bronchus.

METHODS

In this study, we examined the fixation rates of 791 GMs placed in 235 patients (259 procedures), from November 2011 to November 2020, at a single facility. The relationship between the elapsed time and the fixation rate was assessed using the Kaplan-Meier method. Moreover, we measured the distance between the GM and the chest wall (DMC), as confirmed using planning computed tomography, and analyzed the relationship of this distance with the fixation rate.

RESULTS

Overall, 28.8% of GMs dropped out within 10 days of placement. The fixation rate of GMs in the bronchi was significantly lower in the upper lobe than in the other lobes, in both lungs (right, p < 0.01; left, p = 0.05). Moreover, in the left upper lobe, the fixation rate of GMs was significantly lower in B1+2 than in B3 (p = 0.0181). In addition, the group with a short DMC had a significantly higher GM fixation rate. (p < 0.01).

CONCLUSIONS

The fixation rate of GMs was lower in the upper lobes than in the lower lobes. Additionally, the fixation rate was lower in B1+2 than in B3. Shorter DMCs were associated with higher GM fixation rates.