Real-time Guided Stereotactic Radiotherapy in Lung Cancer Using Endovascular Coils for Tumor Marking: Head-to-head Comparison Between Endovascular and Bronchoscopic Fiducial Marker Insertion

The role of radiotherapy is well established in the management of early stage lung cancer or as part of a multidisciplinary approach of locally advanced lung cancer (1).

Recent advances in Cyberknife© technology, which is a robotic system of stereotactic irradiation including localisation and real time lesion-tracking, has led to an increase in accuracy and potentially in efficiency of the irradiation of tumor field (2)(3). According to several studies, promising results in local control and survival rates have been achieved in patients suffering from primary lung cancer or peripheral lung metastasis treated with Cyberknife© (4)(5)(6)(7)(8).

Fiducial markers are implanted in or near a tumor in a configuration defining a COM (center of mass) guiding the Cyberknife for tumor localization.

Tumor movement is then synchronized to respiratory cycle motion during treatment which reduces toxicity of non target lung tissue irradiation. Change in marker positioning leads to COM alterations, thus limiting detection by the tracking system.

Percutaneous (9)(10)(11) (12), endovascular (12)(13) fiducial implantation or by means of bronchoscopic devices (14)(15)(16)(17)(18) are three techniques that have been validated in previous studies as feasible and safe procedures, providing accurate tracking.

Few studies are currently available in the litterature comparing these modalities (19)(20). The percutaneous implantation technique will not be considered for this study because this technique is associated with a high risk of pneumothorax (9).

Both the endobronchial and endovascular technique have been described in the literature with equivalent success rate (87-90%) in intention to treat (21)(22).

One of the endpoints of this study is to verify that these results are reproducible in our institution where both techniques are currently available and to investigate other secondary endpoints such as fiducial marker migration after placement, complications rates and procedure time.