International trial of endobronchial implantation of electromagnetic fiducials for real-time tracking of lung tumors during radiotherapy (RT)

Technologic advance in RT has resulted in dramatic improvement in lung tumor control, but respiratory motion still complicates RT. We present our results implanting anchored electromagnetic transponders (Varian Medical, Palo Alto, CA) providing real-time localization and tracking of tumor position during RT. 50 patients (pts) underwent bronchoscopic implantation of 3 transponders (150 total) in small airways in or near the tumor under fluoroscopy ± electromagnetic navigation or EBUS. Localization and tracking of transponders was performed during stereotactic and conventional RT. Stability was assessed by serial CTs. There were 22 males/28 females, ages 42-88 (med. 64), with 12 tumors in the LUL, 11 in the RUL and 27 in other lobes. Follow-up ranged from 0-12 months (med. 8.2 months). No unique skills were required and implanter satisfaction was high. 46 pts had no significant problems associated with the device or procedure. Two pts developed pneumothorax, resolving overnight with chest tube placement. Three months after RT, 1 pt experienced transponder migration into the pleural space following bronchopleural fistula. 1 pt experienced asymptomatic migration, due to implantation in a larger airway. Markers were successfully localized in all 48 eligible patients, with 1 pt not undergoing RT due to disease progression and 1 pt not undergoing localization due to pacemaker implantation. Bronchoscopic implantation of anchored transponders is feasible with few complications. Transponder stability is high. Real-time localization and tracking of lung tumors is feasible and provides motion information that can be used for RT planning and delivery.