Brachytherapy for Carcinoma of the Lung
Brachytherapy for Carcinoma of the Lung
An estimated 157,000 patients died of lung cancer in the United States in the year 2000. Although surgery can be curative, only about 20% of patients are amenable to complete surgical resection. Most of the other patients are treated with radiation therapy (external-beam irradiation and/or brachytherapy) and/or chemotherapy, with less than 10% surviving to 5 years.
Most patients referred for radiation therapy have large tumor volumes requiring high doses of radiation for control of locoregional disease. Dose escalation with external-beam radiation therapy is limited by tolerance of the surrounding normal structures. Brachytherapy is one method of delivering a higher radiation dose to the tumor while sparing the surrounding normal tissues, in an attempt to improve local control. Small or occult carcinomas of the lung in medically inoperable patients are another subgroup in whom brachytherapy can be used to boost the external-beam radiation dose.
The majority of lung cancer patients eventually have symptoms related to local progression and subsequently die from locoregional failure. Commonly reported symptoms from failure of local control include cough, dyspnea, pain, and hemoptysis, with the majority related to endobronchial disease. Therefore, management of the endobronchial and peribronchial component of lung cancer is quite important, even in patients with metastatic disease. Brachytherapy can be used for palliation in these patients.
The use of brachytherapy for lung cancer is not new. Even as early as 1922, Yankauer described two cases of lung cancer treated endoscopically with radium (Ra)-226. In 1933, Graham and Singer implanted radon-222 seeds into lung tumors, and Ormerod performed transbronchial brachytherapy in 1937. The use of low-energy iodine (I)-125 reduced the radiation safety problems and regulations associated with the earlier radionuclides. Subsequently, the advent of the fiberoptic bronchoscope and the development of the high-activity iridium (Ir)-192 remote afterloader led to a significant increase in the use of endobronchial brachytherapy.
Brachytherapy may be used alone, in combination with surgery, or with external-beam radiation. The intent of treatment may be cure or palliation of symptoms.
Lung brachytherapy techniques vary widely, and only limited guidelines exist for their clinical use. The American Brachytherapy Society (ABS), therefore, formed a panel to issue guidelines specifically for the use of brachytherapy for lung carcinoma.
Selected members of the ABS with expertise in lung brachytherapy performed a literature review, which, supplemented by their clinical experience and biomathematical modeling, allowed formulation of specific recommendations and directions for future investigations in lung brachytherapy. These recommendations were made by consensus and supported by evidence in the literature, whenever possible. The consensus levels used by the ABS are similar to those of the National Comprehensive Cancer Network and are defined as follows:
Category 1: There is uniform panel consensus, based on published literature, that the recommendation is appropriate.
Category 2: Recommendation is based on low-level evidence, including nonpublished clinical experience. There is no major disagreement among panel members.
Category 3: There is major disagreement among panel members that the recommendation is appropriate.
This initial report was revised based on the comments of external experts, including some who were ABS members and some who were not. The board of directors of the ABS approved this final document.
The results of the deliberation of the panel and the ABS recommendations are given in the following sections. Unless specifically noted, these recommendations generally reflect a level 1 consensus.
Bronchoscopic and Catheter Insertion
The ABS made the following recommendations regarding bronchoscopic and catheter insertion techniques. Readers may refer to standard textbooks for procedural details.[7-9]
The ABS recommends that brachytherapy be performed with flexible fiberoptic bronchoscopy via the transnasal approach, with the patient under conscious sedation. Sedation should be administered by individuals who are properly trained and familiar with this approach. Intensive monitoring (eg, of blood pressure, pulse oximetry, and cardiac status) is required, and appropriate medical personnel and monitoring equipment (including electrocardiogram for high-risk patients) must be available.
The tumor should be visualized through the bronchoscope and photographed, if possible, for documentation and comparison on follow-up examination. The tumor location in the tracheobronchial tree, percentage of lumen occlusion, and length of airway involvement should all be recorded for dose prescription purposes.
The catheter tip should be placed at least 2 cm beyond the most distal aspect of the tumor, whenever possible. Localizing the tip in a segmental bronchus helps to hold the catheter in place. It should be noted that the endobronchial lesion is usually well visualized under bronchoscopy but not under fluoroscopy. Conversely, the catheter tip with the guidewire in place can usually be clearly seen under fluoroscopy, but the tip’s position in relation to the distal end of the tumor is harder to verify on bronchoscopy.
Graduated markings on the catheter help determine its location relative to the tumor. If premarked catheters are not available, marking the distal portion of the catheter at 5-cm intervals before insertion provides these visual reference points for catheter placement and treatment planning (category 2). Although the exact length to be treated depends on the extent of bronchial (or tracheal) involvement, lengths of 5 to 7 cm are commonly irradiated.
Centering devices (balloons, cages, and sheaths) can help to reduce dose inhomogeneity in the bronchial wall (category 2). The ABS deems centering devices to be optional, depending on physician preference.
When required by the tumor location, two or more catheters should be used to achieve adequate dosimetric coverage. In this situation, the first catheter is placed through the bronchoscope into the desired location, and the bronchoscope is withdrawn while the catheter remains in place. The bronchoscope is subsequently reintroduced, and a second catheter is placed in the desired location in the adjacent bronchus. Multiple catheters are commonly used in tumors located at the major or minor carina.
Fluoroscopy should be used to visualize the guidewire during insertion and to confirm that the catheter is not displaced as the bronchoscope is removed. The external end of the catheter should be adequately secured to the patient’s nose and marked with an ink pen at the nostril edge to allow an additional visual check that the catheter has not migrated.
Upon treatment completion and catheter removal, the patient and room should be surveyed to rule out any radioactive source misplacement. The patient should be observed after the procedure and discharged only when stable.