The evaluation of a peripheral nodule is a common challenge in pulmonary medicine. It is estimated that 150,000 pulmonary nodules are found each year in the United States of America.1 A recent surveillance program with computed tomography (CT) scanning found pulmonary nodules in over 20% of the screened population.2 These nodules represent a dilemma for clinicians. Most nodules are of benign etiology and do not need further diagnostic or therapeutic intervention. However, a significant percentage, 10% or greater, are malignant and early intervention is essential.2,3 The dilemma further extends to the selection of the diagnostic test. Which technical approach is most likely to yield the diagnosis with the least risk of complications? Diagnostic modalities range in invasiveness from watchful waiting to thoracotomy. The selection of diagnostic tool is based on the degree of suspicion for malignancy and the characteristics of the nodule.2,3
Although there are several diagnostic interventions, none is ideal. CT-guided biopsy has become a powerful tool in the evaluation of pulmonary nodules and masses. The pooled sensitivity for detecting malignancy with CT-guided percutaneous transthoracic fine needle aspiration (FNA) was 86% in a meta-analysis of 48 studies. However, CT-guided FNA has a high complication rate; 25% pooled incidence of pneumothorax.4 If the risk for malignancy is high, thoracotomy can provide both diagnosis and therapy. Unfortunately, almost 50% of thoracotomies yield a benign diagnosis and are therefore unnecessary.1 When the patient has significant comorbidities, real-time CT-guided transbronchial needle aspiration is an attractive option. The drawbacks are increased radiation exposure, technical challenges owing to positioning in the scanner, and scheduling obstacles.1 The electromagnetic navigational (EMN) system was developed to provide the endoscopist with a virtual CT-guided bronchoscopy. EMN bronchoscopy provided a diagnosis in 69% to 74% of peripheral lesions with minimal complications in 2 recent series.5,6 This noninvasive procedure avoids the obstacles of real-time CT-guided bronchoscopy, percutaneous FNA, or surgical resection.
This article describes a novel use of the EMN system. After the diagnostic procedure, the system can be used to guide therapeutic interventions. If the lesion is found to be malignant, EMN can guide implantation of linear radiotherapy monitoring devices (RMDs), also known as fiducial markers. There are 2 benefits of RMD implantation. If the treatment plan is palliative, the RMD will provide accurate target identification and precise patient positioning for focused, dose-delivery procedures such as intensity-modulated radiation therapy and conformal radiation therapy.
Radiotherapy is frequently used for the treatment of inoperable lung cancer. New approaches to radiotherapy, such as intensity-modulated radiotherapy, allow higher doses of radiation to the target volume without increased toxicity to surrounding tissue.7 RMDs allow precise targeting and definition of the lesion over the continuum of therapy. This approach is particularly attractive for treating malignancies of the lung since the structures within the thorax are in constant motion. A recent study found stereotactic high-dose radiotherapy was effective in treating unresected stage I lung cancer. When used to treat operable stage IA and IB lung cancer in patients who refused surgery, it was associated with a 5-year survival of 90% and 84%, respectively; compared with traditional survival rates after surgical resection of 55% to 72%.8
If the treatment is surgical, RMDs can be used to guide surgical resection. Endoscopically placed coiled RMDs used in conjunction with fluoroscopy are effective in guiding resection.9 In our experience, coiled RMDs are effective in guiding both radiation and surgical interventions (Fig. 1).
The techniques described in this vignette provide a mechanism for implantation of RMDs within lung nodules using EMN bronchoscopy.
MATERIALS AND METHODS
All bronchoscopies were performed using an Olympus Model 160 bronchoscope, processor, and light source (Olympus Medical Systems Corp, Tokyo, Japan).
Real-time virtual bronchoscopy is made possible with superDimension/Bronchus system (superDimension Ltd, Herzliya, Israel). The system uses a 3-dimensional CT reconstruction software package and an electromagnetic probe and mat. A guidable extended working channel (EWC) is used to steer the probe into distal airways. The system and devices have been described in detail previously.5
A Wang, 21 or 19-gauge, needle (ConMed Corp, Utica, NY) is used for diagnostic FNA. A Wang, 19-gauge, histology needle with inner 21-gauge needle (MW-319) is used for implantation of the RMD.
A 5-french JB1 angulated Benton-Hanafee-Wilson Glidecath catheter (Boston Scientific Corp, Natik, MA) is used for deploying the RMD (Fig. 2). The angulated catheter allows the interventional bronchoscopist to place the RMDs in a radial pattern.
The RMD employed in this technique is the Visicoil sterile coiled gold fiducial marker, 0.75-mm diameter (RadioMed Corp, Tyngsboro, MA). The Visicoil comes in various lengths. We prefer to use the 20-mm length but the appropriate size varies with the size of the lesion. We have used 10 and 30-mm length markers as well. Using RMDs of differing lengths in the same lesion can also be helpful to the radiation oncologist.
A 0.66-mm-diameter guidewire (SCIMED CHOICE PT Extra Support, Boston Scientific, Miami, FL) is used to extrude the RMD from the Wang needle for final placement. The wire is firm enough to transfer pressure through the needle or glide catheter and long (182 cm) enough to be used with either system.
Informed consent is obtained before every procedure. Patients who are at high risk of having malignant lesions are given presumptive clinical staging based on CT scan before the procedure. EMN bronchoscopy is performed after appropriate planning using the superDimension software. The EWC is advanced into the small airways with the electromagnetic probe. The electromagnetic mat serves to localize the probe and the software matches the location to the virtual bronchoscopy image generated from the 3-dimensional reconstruction of the chest CT. After the probe and EWC have been positioned adjacent to the target lesion, the probe is removed and an FNA is performed. After FNA, rapid on-site cytologic evaluation (ROSE) is carried out to determine the preliminary diagnosis. If the lesion is found to be malignant and the treatment plan includes radiotherapy or resection, then a RMD implantation is initiated.
We have used 2 methods of implanting RMDs through the EWC. The first method employs a 19-gauge Wang needle, the “needle method.” The second method of implanting the RMDs requires an angulated tip glide catheter, the “catheter method.” We will describe both methods separately.
Once the electromagnetic probe and EWC have been advanced to the lesion, and the diagnosis has been achieved, the 19-gauge Wang needle (MW-319) is inserted. This needle could be the same one used to establish the diagnosis. Using fluoroscopic guidance, the needle is advanced past the EWC and inserted into the lesion. The inner 21-gauge needle is completely removed, leaving the 19-gauge needle and sheath. The RMD is back loaded into the needle sheath and a 0.66-mm guidewire is used to push the RMD through the length of the sheath. The needle is slowly pulled back as pressure is maintained on the guidewire to prevent dislodging the RMD. If radiotherapy is planned, we attempt to place 3 RMDs in a radial pattern when the size of the lesion permits. Fluoroscopic guidance for resection can be achieved with a single RMD.
The catheter method is our favored method of delivery. The benefit of this delivery method is the ease in which RMDs can be placed in a radial pattern.
After the lesion has been located and a diagnosis has been achieved, the angulated catheter is advanced through the EWC into the lesion. The RMD is loaded into the proximal end of the catheter and a 0.66-mm guidewire is placed through the catheter and under fluoroscopic guidance, the RMD is deployed. Because the glide catheter is angulated, it can be turned in different directions, allowing placement in different planes of the tumor.
Once the RMDs are placed by either method, their position is confirmed fluoroscopically and the working channel and bronchoscope are then removed (Fig. 3). CT scans have been used to follow the location of the RMDs during the course of radiotherapy (Fig. 4).
The development of the EMN bronchoscopy system provides a new tool for diagnosis of lung lesions. We describe a method that supports therapeutic utility as well. It is anticipated that through the use of RMD implantation in peripheral lung cancers, that more efficient, highly selective stereotactic external beam radiation therapy could be performed in these individuals. This new technology may lead to decreased morbidity and mortality in these individuals.
The Japanese multicenter trial evaluating hypofractionated high-dose stereotactic radiation for stage I lung cancer had surprising benefit for those with operable disease who refused surgery. These patients had an 88% 5-year survival. This reproduced the findings of a prior single center study of this approach. The overall 5-year survival rate for both operable and inoperable patients with stage I was over 60% in the arm that received high-dose stereotactic radiation.8 As a result, several centers have begun using targeted radiotherapy for nonresectable lung cancer.
The new techniques described in this article allow for the placement of RMDs in lung lesions. Particularly, the angular catheter system for placement of RMDs seems to be highly accurate and has the advantage of being able to place the catheter into the lesion and then load the Visicoil markers through the proximal port in the catheter system. Furthermore, the angulated catheter allows the placement of RMDs in multiple planes without withdrawing the catheter. This should improve the accuracy of stereotactic radiation therapy by giving a 3-dimensional target for the radiation oncologist. In future procedures, plan to exclusively use the angulated catheter device because it has many advantages over the MW-319 Wang needle system. Most importantly, placement of the VC markers with these new techniques was not associated with any morbidity or mortality. This is in contrast to attempts to place these markers percutaneously using CT guidance, which has been fraught with many complications, most importantly pneumothoraces.10–12 We believe that this approach will also overcome the obstacle of RMD loss or displacement seen in another endoscopic approach.13
There are several design options for fiducial markers. The type of RMD or fiducial marker that we are employing has several advantages. One is the flexibility of the coiled marker. The other is the length. Together these characteristics allow ease of radial placement. We feel the coiled design lessens potential for migration. In our experience, these RMDs have not been associated with hemoptysis, migration, nor have led to embolization.
The drawbacks to this approach include the need for ROSE. Without this service, it would not be possible to confirm the correct insertion site for the markers. We feel ROSE is an invaluable service for all approaches to pulmonary and mediastinal cytology. But, it is a luxury that not all institutions have. The cost of the EMN bronchoscopy is also an issue. There is neither dedicated coding nor compensation from Medicare for the diagnostic procedure. The hardware and software costs well exceed $100,000. Disposable materials costs surpass 1000 US dollars per case making routine use financially onerous.
In summary, the present article describes a technique for the placement of RMDs within peripheral lung cancers. We believe that the angulated glide catheter technique for placing RMDs provides the most accurate and safe method for marking lung tumors for subsequent highly selective radiation therapy. We anxiously await treatment outcomes in our patients to see if this approach decreases morbidity and mortality in these individuals.
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Keywords:© 2007 Lippincott Williams & Wilkins, Inc.
electromagnetic navigational bronchoscopy; radiotherapy monitoring device; fiducial marker; conformal gated radiotherapy; stereotactic radiation; lung nodule; lung cancer