While radiation is rarely used as a first-line therapy for mesothelioma, it is more commonly used either as palliative care or as an adjuvant therapy to help remove remaining cancer cells after surgery. Doctors may recommend radiation as a primary treatment if a patient has low-stage mesothelioma but is not a good surgical candidate.
Despite extensive use among mesothelioma patients, there is no standard radiation therapy method for this cancer. The radiation dose is determined by two factors: the necessity of irradiating the entire side of the chest affected by the disease and the concern for the radiation sensitivity of the heart, lung, esophagus, liver, and spinal cord. Because radiation treatment kills non-cancerous cells as well, if it is not carefully dosed and targeted, it can cause serious and even fatal side effects.
The whole radiation dose is fractioned or spread out over a period of time to give normal cells time to recover between treatments and to let tumor cells that were in a radiation-resistant phase of their cell cycle move on to a phase more responsive to radiation before the next treatment.
Types of Radiation Therapy for Mesothelioma
Intensity Modulated Radiation Therapy (IMRT)
Radiotherapy is a common adjuvant treatment after cancer surgery but adapting the technique for mesothelioma patients was not easy. Early attempts at radiation therapy caused high levels of toxicity in patients. However, with the improvements offered by IMRT, technicians can more easily target the cancer without affecting surrounding cells as much. Subsets of this treatment method that have been successfully piloted include helical tomotherapy (HT), volumetric arc therapy (VMAT), and Intensity Modulated Pleural RadIatioN Therapy (IMPRINT). All forms of IMRT use X-ray beams to irradiate tumors.
Almost every case of radiation therapy for mesothelioma patients uses IMRT thanks to its ability to target complex geometries. Though there is still a chance for patient toxicity, it has decreased in recent years and will hopefully continue to do so.
Brachytherapy
Brachytherapy is an internal radiation treatment where a patient has radioactive “seeds” implanted in the cancerous tissues. The benefit of this form of treatment is that it allows the doctor to administer a higher dose of radiation in a shorter period of time. When used for mesothelioma, brachytherapy is instituted during the same surgery used to remove tumorous growths.
There are 2 brachytherapy methods that can be used in mesothelioma patients. The first requires at least a centimeter’s margin around the cancerous cells that could not be removed. For this therapy, radioactive iodine seeds are woven into a degradable mesh-like fabric that is then placed as a “cover” for the mesothelioma. The radiation is delivered in doses spread out over three months, but the residual radioactivity can last up to a year.
When this procedure is used to treat other forms of cancer, it is done on an outpatient basis. However, when it is used in the treatment of mesothelioma, it is done intraoperatively, meaning as part of the operation that is performed to debulk or remove as much of the tumor as possible. Intraoperative Radiation Therapy (IORT) should not add to the overall operative time.
There are two methods of brachytherapy that are performed intraoperatively. The relatively newer procedure involves a measure of the chest cavity in which the tumor was not able to be removed with a minimum of one-centimeter clear margin. In this instance, the implanted mesh is biodegradable. It is stitched in a manner that creates a cover for the area that has the remaining mesothelioma.
The second, older procedure uses catheters positioned in the remaining tumor(s) or growths. Radioactive iridium pellets are inserted via catheter once each device has been carefully positioned. The location and duration of each exposure are digitally controlled. At the end of the treatment, the pellets and catheters are removed—no radioactive materials are left in the body.
Currently, brachytherapy is used only in clinical trials for mesothelioma treatment.
Radiation Therapy Side Effects
Toxicity is an expected reaction to radiation, though thankfully most patients experience lower levels (Grade 1 or 2) of this condition. Side effects may include:
- Skin redness near the irradiated site
- Fatigue
- Nausea, vomiting, or loss of appetite
- Chest discomfort
- Lethargy
- Hair loss
- Decreased blood cell counts
For patients who receive radiation treatment after pleurectomy/decortication rather than extrapleural pneumonectomy, radiation must be carefully targeted to avoid damaging the lung. Otherwise, patients may develop radiation pneumonitis, a serious inflammation of the lungs.
You can take some steps to help you relieve some of these side effects. The American Society for Radiation Oncology recommends that you:
- Get plenty of rest.
- Call your doctor if you experience a fever of 101 degrees or higher.
- Avoid using any lotions, perfumes, deodorants, or powders in the treatment area unless approved by your doctor or nurse. Try not to use products containing alcohol and perfumes.
- Avoid putting anything hot or cold on the treated skin. This includes heating pads and ice packs.
- Stay out of the sun. If you must be outdoors, wear clothing to protect your skin. After treatment, use sunscreen with an SPF of at least 15.