INTRODUCTION: Many patients with lung cancer have comorbidities that preclude surgical resection. One option for such patients is stereotactic radiosurgery (SRS)1. Traditionally, SRS has relied upon the percutaneous placement of gold fiducial markers (FMs) by computed tomography (CT) guidance. With this approach there is a comparatively higher rate of pneumothorax than with bronchoscopic techniques2. Electromagnetic navigation (EMN) and peripheral endobronchial ultrasound (EBUS) can be used to bronchoscopically guide FMs to parenchymal lesions. We present the use of convex probe EBUS for placement of FMs in a parenchymal tumor.
CASE PRESENTATION: A 65 year-old morbidly obese patient (body mass index 62) was found to have a 2.1 cm left lower lobe nodule. Positron emission tomography-computed tomography (PET-CT) was suggestive of malignancy in the lesion but not elsewhere. Convex-probe EBUS transbronchial needle aspiration was used to diagnose the lesion as squamous cell carcinoma. Levels 7, 11, and 12 lymph nodes were cytologically negative during EBUS-staging. She was referred to, but declined, surgical resection. A request was made for fiducial placement to guide SRS. No clear airway visibly led to the central lesion, so EMN and peripheral EBUS were not acceptable methods for accurate FM placement. Convex probe EBUS was therefore used to identify the parenchymal nodule. A 0.35 x 20 mm gold fiducial marker was front-loaded into the 22-gauge EBUS needle. The needle punctured the nodule and the fiducial marker was deployed using the EBUS stylet. The marker was observed by ultrasound to be deployed within the nodule. This was repeated for a total of 4 markers. Subsequent SRS imaging planning demonstrated that the markers were located in the middle of the malignant lesion.
DISCUSSION: Although surgical resection is the preferred treatment for early-stage lung cancer, patient comorbidities may preclude a safe operation. In these cases, stereotactic radiosurgery is being used in an effort to cure the patient. The lung poses a unique challenge to the use of SRS because respiratory movement creates a dynamic target for the radiation beam. This problem was addressed in the 1990s with the development of a respiratory tracking device that detects gold rods called fiducial markers (FMs). The accurate placement of FMs is important to enhance dosing to the target area while minimizing doses to adjacent tissue. The traditional approach using percutaneous CT-guidance unfortunately carries a high rate of pneumothorax. Peripheral EBUS combined with EMN have been used to successfully place FMs for SRS3; this approach works best when an airway leads to the lesion. Convex probe EBUS has been described for guiding FMs in peribronchial malignant lymph nodes to guide external beam radiation therapy. Esophageal ultrasound (EUS) FM placement has been described for intra-abdominal malignancies and mediastinal lymph nodes. To our knowledge, this is the first report of convex-probe EBUS being used to place fiducial gold markers in a parenchymal lung tumor for SRS.
CONCLUSIONS: Convex probe EBUS-guided fiducial marker implantation is feasible for centrally-located parenchymal lung tumors in patients considered for stereotactic radiosurgery.
Reference #1 Scott WJ, Howington J, Feigenberg S, Movsas B, Pisters K. 2007; Treatment of Non-small Cell Lung Cancer Stage I and Stage II: ACCP Evidence-Based Clinical Practice Guidelines (2nd Edition). Chest 132, 234S-242S.
Reference #2 McGuire, R, Liming, J, Ochran, T, Kerley JM, McLemore TL. 2007; Real-time Endobronchial Ultrasound-guided Implantation of Radiotherapy Monitoring Devices. J Bronchol 14, 1 59-62.
Reference #3 Harley DP, Krimsky WS, Sarkar S, Highfield D, Aygun C, Gurses B. 2010; Fiducial Marker Placement Using Endobronchial Ultrasound and Navigational Bronchoscopy for Stereotactic Radiosurgery: An Alternative Strategy. Ann Thorac Surg 89, 368-74.
DISCLOSURE: The following authors have nothing to disclose: Lauren Tobias, Roy Decker, Jonathan Puchalski
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