PURPOSE: Stereotactic radiosurgery is a treatment option for patients with inoperable lung cancer. However, problems in targeting radiotherapy include changes in tumor position which are due to the normal respiratory cycle, and unpredictable baseline shifts in respiratory rates and amplitude. Fiducial markers inserted into or near the tumor are useful for real-time tracking of tumor position during radiation. Traditionally, markers placed under transthoracic CT-guidance have been associated with a high frequency of pneumothorax, and those placed with conventional bronchoscopy have a high incidence of marker migration or inaccurate placement due to limitation in distal airway size. To minimize complications and enhance accurate placement, electromagnetic navigational bronchoscopy(EMNB) can be used for implanting markers.
METHODS: Patients deemed medically inoperable with peripheral lung tumors, underwent EMNB for placement of fiducial markers. During planning phase, all patients had multiplaner high resolution CT-imaging. Precise localization of the tumor was achieved using a steerable locatable guide with an extended working channel through which a pre-loaded Wang TBNA needle with a 1-cm viscoil fiducial marker could be placed. Placement was confirmed fluoroscopically. After fiducial marker placement, radiotherapy planning was done using a three-dimensional CT-based planning system. The procedure was deemed successful if markers were implanted within or near the tumor without migration at time of radiosurgery.
RESULTS: Fiducial markers were placed at two different centers using EMNB. A total of 20 markers were successfully implanted in 14/14 patients(100%). Mean tumor diameter was 2.6cm (range 1.0-6.0cm). At time of radiation CT-planning, day 13+/-22 days, marker stability was noted in all patients with no migration. No procedure related complications were noted.
CONCLUSION: Fiducial markers allow higher doses of radiation to be delivered to target sites with greater accuracy. However, two issues must be addressed with the deployment of markers: the implantation technique and the stability of the marker.
CLINICAL IMPLICATIONS: EMNB can be used both safely and accurately to implant fiducial markers for radiosurgery without the complications of pneumothorax from transcutaneous placement, or increased migration rates seen with conventional bronchoscopy.
DISCLOSURE: Sandeep Bansal, None.