Pulmonary Medicine

Interventional Bronchoscopy: Brachytherapy

General description of procedure, equipment, technique

Brachytherapy

Initially defined in 1995 and subsequently described in European Respiratory Society (ERS) and American Thoracic Society (ATS) guidelines, interventional pulmonology is "the art and science of medicine as related to the performance of diagnostic and invasive therapeutic procedures that require additional training and expertise beyond that required in a standard pulmonary medicine training program." Clinical entities encompassed within the discipline include complex airway management, benign and malignant central airway obstruction, pleural diseases, and pulmonary vascular procedures.

Diagnostic and therapeutic procedures pertaining to these areas include rigid bronchoscopy, transbronchial needle aspiration, autofluorescence bronchoscopy, endobronchial ultrasound, transthoracic needle aspiration and biopsy, laser bronchoscopy, endobronchial electrosurgery, argon-plasma coagulation, cryotherapy, airway stent insertion, balloon bronchoplasty and dilatation techniques, endobronchial radiation (brachytherapy), photodynamic therapy, percutaneous dilatational tracheotomy, transtracheal oxygen catheter insertion, medical thoracoscopy, and image-guided thoracic interventions. This presentation focuses on brachytherapy.

Endobronchial radiation therapy by the use of an implanted source of ionizing radiation (brachytherapy) was first used in the 1920s. Yankauer reported on the implantation of radium into an endobronchial tumor using a bronchoscope, with the radium in capsules attached to a string that exited through the mouth.

In the mid-1980s, publications distinguished low-dose-rate (LDR) from high-dose-rate (HDR) brachytherapy. LDR brachytherapy is usually defined as delivery of less than two gray (Gy) per hour and a total dose between 15 and 50 Gy, given over three days. HDR entails delivery of more than ten Gy per hour, in which the total dose and the dose per session varies from approximately 3 to 10 Gy, and total dose from approximately 5 to 40 Gy. Development of the "remote afterloading device" reduced the radiation exposure to the healthcare staff.

Subsequently, use of the flexible bronchoscope and the polyethylene catheter that holds the radioactive material for brachytherapy was described, along with a description of Iridium-192, the current radiation source.

Indications and patient selection

The indications for brachytherapy are similar to those for the other endobronchial therapies. The therapeutic goal is palliation of symptoms caused by airway obstruction by tumor. Some investigators have used the technique in patients who have histologically positive surgical margins following surgical resection, or for treatment of radiologically occult endobronchial carcinomas. Brachytherapy used as an adjunct to external beam radiotherapy for treatment of otherwise unresectable lung cancers is no longer recommended. Radical endobronchial brachytherapy is only recommended in the context of a clinical trial.

Contraindications

Absolute contraindications for endobronchial brachytherapy include known fistulas to non-bronchial tissue areas and lesions that have not been proved to be malignancies. Because of the potential for post-radiation edema and total airway obstruction, patients with endotracheal carcinoma that causes high-grade obstruction should be treated with Nd: YAG laser and possible stent placement prior to brachytherapy.

Details of how the procedure is performed

HDR intraluminal brachytherapy currently uses flexible bronchoscopy for the placement of a polyethylene catheter and a wire with radio-opaque 1 cm graduations. The wire is then used to calculate delivery and dwell positions for the radioactive source. Positioning of the catheter and the wire is confirmed by bronchoscopy and radiography. After removal of the wire, the radiation source is delivered into the catheter by machine for the prescribed dwell time.

The dose rate of brachytherapy depends on the radioactivity of the radionuclide used. Current guidelines state that HDR is preferred over LDR. The apparatus designed to deliver HDR brachytherapy uses iridium 192, which is the radionuclide of choice. HDR brachytherapy can be delivered as fractionated doses, but recent information suggests that a single fraction is as safe and efficacious as multiple fractions. If multiple fractions are used, suggested treatment schedules are once per week or every two weeks to achieve a total dose of 14 Gy to 30 Gy.

Interpretation of results

Not applicable.

Performance characteristics of the procedure (applies only to diagnostic procedures)

Not applicable.

Outcomes (applies only to therapeutic procedures)

Subjective improvement after brachytherapy has ranged from 20 percent to 100 percent, depending on the symptoms. Hemoptysis is relieved in more than 90 percent of patients, but cough and dyspnea are only moderately or minimally relieved, probably because of underlying of chronic bronchitis or radiation fibrosis. Most studies report greater than 50 percent improvement in airway patency, and positive responses usually persist for six months or more.

Conventional external-beam radiation therapy relieves symptoms of hemoptysis, dyspnea, or chest pain in 50-80 percent of patients for three to four months. In studies that have compared conventional radiation to brachytherapy, there has been a slight trend toward better palliation with brachytherapy, but patients treated with brachytherapy required more subsequent interventions. The number of patients included in these studies was small.

In one study of 16 patients with endobronchial carcinoma, local control rates were > 80%, but 10 of the patients also received conventional radiation. Brachytherapy to treat a positive surgical margin and local stump recurrence after surgery appears to be potentially beneficial. Based on existing data, guidelines on endobronchial brachytherapy support its use as a possible choice in palliation of malignant airway disease. If the lung or lobe is collapsed at first presentation, brachytherapy might be considered a first choice in palliation due to improved results over external beam radiotherapy.

Alternative and/or additional procedures to consider

Not applicable.

Complications and their management

Brachytherapy has both early complications and late complications. The two most serious complications are massive hemoptysis and fistula formation to the mediastinum. Several large series have reported a rate of serious complications of 0-42 percent. Risk of massive pulmonary hemorrhage is likely related to the proximity of pulmonary arteries to the left upper lobe bronchus. In one report, massive hemoptysis following treatment occurred at a rate of 32 percent in patients with recurrent tumors in the right upper lobe bronchus, the right mainstem bronchus, and the left upper lobe bronchus.

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