What is Brachytherapy?
Unlike traditional radiation therapy, brachytherapy uses no external radiation. Because of this defining property, it may also be referred to as internal radiation therapy, whereas the traditional type may be called external beam radiation therapy (EBRT).
Currently, internal radiation is not standard treatment in either lung cancer or mesothelioma, but researchers continue to test the treatment in clinical trials. Results from early studies show potential for brachytherapy to be used to extend life span and reduce the severity of symptoms.
A March 2021 study reported that thoracic cancer patients who receive brachytherapy benefit from fewer and less severe side effects after pulmonary surgery.
So far, it is more effective in treating lung cancer. Researchers saw the best results for both types of cancer when they implemented a type of the treatment called permanent brachytherapy. In this type, a radioactive material is placed permanently into the tumor site and slowly loses its radioactivity over a few months.
Brachytherapy is administered using a radioactive material called an implant. The material may come in the form of a wire or a “seed” about the size of a grain of rice.
It may be placed during surgery, a technique known as intraoperative radiation therapy (IORT), or the implant may be inserted into cancer tissue using a hollow tube. In this type of administration, the patient receives local or general anesthesia, and the doctor typically uses the aid of an imaging scan such as a CT scan or ultrasound. Once the implant is in place, it typically only attacks tissue within a radius of 1cm. This can be more effective, but requires precision.
This therapy may be combined with other treatments. IORT brachytherapy is always administered in conjunction with surgery, and some lung cancer patients receive standard brachytherapy after surgery to kill any remaining cancer cells.
The treatment also may be used alongside conventional radiation therapy to target tumor growth in multiple ways. Depending on each patient’s situation and treatments, it may be used as a potentially curative treatment to try to eradicate the cancer, or it may be used as a palliative treatment to reduce symptoms such as coughing and difficulty breathing.
Due to the sharp radiation dose fall-off with brachytherapy, in some cases it may be associated with fewer side effects than external beam radiation therapy. The most common side effect is tenderness at the site of insertion, which subsides after a few months. Patients may also experience temporary swelling at the treatment site.
Types of Brachytherapy
There are two primary types of brachytherapy: low-dose rate and high-dose rate. People with lung cancer or mesothelioma usually receive a form of low-dose rate treatment called permanent brachytherapy. This type continuously attacks the tumor with radiation for several months.
Depending on the type of therapy a patient receives, he or she may undergo treatment for up to several weeks. This is shorter than the time needed to complete an external beam radiation therapy regimen, which can take up to 10 weeks.
Low-dose rate (LDR) brachytherapy involves low doses of radiation for long periods of time. For this treatment, radioactive material may be left in place for up to a week.
The radiation can be harmful to people nearby, so patients remain in the hospital while receiving the treatment. Patients typically stay in private hospital rooms and cannot have guests for extended periods of time. LDR brachytherapy should not be painful or uncomfortable.
This is a type of LDR that involves permanently leaving seed implants in the body. This is the most common type used to treat mesothelioma and lung cancer because it has the most improved patient survival rates in clinical trials.
Typically, the implant is inserted during surgery as a form of IORT. Radioactive seeds are woven into a flexible mesh, which is then stitched into place during a surgical procedure such as pneumonectomy or pleurectomy/decortication. This type of brachytherapy, designed to kill cancer cells which cannot be removed with surgery alone, actively emits radiation for about three months. Seeds may be mildly radioactive for another year. The inactive seeds then remain in the body permanently.
High-dose rate (HDR) brachytherapy involves high doses of radiation for a maximum of 20 minutes. The patient receives HDR treatment once or twice daily for a series of days or weeks. After the physician inserts the seed via a tube, he or she typically leaves the room while the radioactive material is in place.
It does not require a hospital stay and, like LDR brachytherapy, is not painful or uncomfortable.
To date, this therapy has not been studied extensively in mesothelioma patients, and researchers have only conducted small trials with varying results. Doctors have conducted more thorough trials of the treatment in lung cancer patients and have observed better results.
A 2005 study treated 123 cases of pleural mesothelioma to test the advantages of the therapy. All patients underwent pleurectomy/decortication and conventional radiation therapy, and almost half additionally received brachytherapy. Researchers concluded that this treatment combination, with or without brachytherapy, was not enough to successfully control growth of mesothelioma.
Despite this study, brachytherapy is still considered a viable treatment option in mesothelioma, and studies continue to test its efficacy. Some treatment centers that specialize in mesothelioma, like Brigham and Women’s Hospital, always consider brachytherapy as an option when creating a treatment plan for a mesothelioma patient.
According to a 2013 review of radiation therapy approaches for thoracic tumors, brachytherapy is not being widely used in the treatment of mesothelioma. However, research on bronchial brachytherapy as a treatment for lung cancer continues.
Lung Cancer Studies
Brachytherapy is more successful in treating lung cancer. In one study, 129 lung cancer patients received LDR or permanent brachytherapy. A quarter of these patients survived five years or longer, as compared with only 15 percent of all lung cancer patients.
According to a 2018 study published in the Journal of Contemporary Brachytherapy, researchers are investigating whether using a CT scan to map the location and size of tumors could improve the application and outcomes of brachytherapy in lung cancer patients. While more research is necessary to determine effectiveness, initial results suggest that brachytherapy can deliver more radiation to a lung tumor than stereotactic body radiation therapy.
In other studies, researchers found high dose rate brachytherapy to be most effective as a palliative treatment for lung cancer patients, easing chest pain and shortness of breath. Studies report that HDR brachytherapy is most effective in reducing symptoms when it is used after external beam radiation. However, HDR brachytherapy still has limited use because it has not been found to increase life span in lung cancer patients.