What Is Radiation Therapy for Mesothelioma?
Radiation therapy for mesothelioma uses energy from radiation to kill cancer cells. Specifically, cancer-directed radiation therapy uses ionizing radiation. Ionizing radiation occurs in two major forms: photon radiation and particle radiation.
- Photon beam radiation is the most common form of radiation cancer treatment. It uses the same form of radiation as an X-ray but at a much higher dose. Photons can release energy at any point along their path, entering, traveling through and exiting the body. This property allows photon radiation to shrink tumors, but it can also damage healthy tissue.
- Particle radiation uses either electrons or protons to deliver energy to cancer cells. Protons only release energy at a specific distance from their source. Thus, proton radiation can kill cells at the end of its path while causing minimal damage to tissues along the way. This property may allow proton radiation to cause fewer side effects than photon beam radiation.
Note: Proton beam radiation requires specialized equipment. It is not yet widely available.
Some forms of radiation can deliver more energy to tissues further below the skin than others. Thus, some types of radiation may be more effective in targeting tumors far below the skin. Radiation specialists consider the properties of each form of radiation. Doctors keep these properties in mind when prescribing radiation therapy. Radiation may extend life expectancy for some mesothelioma patients.
02. How Radiation Works
How Does Radiation Treat Mesothelioma?
Doctors use beams of radiation to damage DNA in mesothelioma cancer cells. When cancer cell DNA is severely damaged, the cells die and can no longer replicate. This may help prevent metastasis or the spread of mesothelioma.
In general, radiation affects fast-growing cells more quickly than slow-growing cells. Thus, fast-growing cells, such as those in bone marrow and skin, may die shortly after treatment. Slower-growing cells, such as those in the brain or nerves, may take longer to die. Damaged cells may continue to die for days, weeks and months after the radiation treatment.
Doctors may use radiation in an effort to eradicate mesothelioma cancer cells. This is called therapeutic treatment. Doctors may also use radiation to minimize symptoms of mesothelioma. Symptom and quality-of-life motivated treatment is called palliative treatment.
Which Forms of Mesothelioma Receive Radiation Therapy?
Doctors and researchers have tested radiation therapy in every form of mesothelioma. Radiation therapy has proven beneficial in pleural mesothelioma patients. However, it has not worked well for peritoneal mesothelioma patients.
Thus, pleural mesothelioma patients commonly undergo radiation therapy, but peritoneal mesothelioma patients do not.
Radiation as Part of Multimodal Mesothelioma Therapy
Physicians commonly prescribe radiation therapy as part of a multimodal treatment plan for mesothelioma. Multimodal treatment combines more than one form of mesothelioma treatment such as surgery, chemotherapy and radiation. Research shows multimodal therapy may lead to superior survival in mesothelioma patients.
Radiation may occur as a pre- or post-surgical therapy. In either case, radiation energy can damage or kill tumor cells. This may delay or prevent tumor spread after surgery.
One of the most successful studies of multimodal mesothelioma treatment is the SMART trial. SMART stands for Surgery for Malignant Pleural Mesothelioma After Radiotherapy. Patients in the SMART trial received high-dose radiation therapy prior to surgery.
The SMART method achieved one of the highest reported median survival results for malignant pleural mesothelioma. Read more about the SMART trial in the study spotlight below.
Palliative Radiation Therapy
Mesothelioma patients can receive palliative treatment at any time after diagnosis. Palliative radiation therapy may be used more often in patients with stage 3 or stage 4 mesothelioma. In these stages, doctors use radiation to shrink tumors and reduce symptoms.
Tumors at these stages may press on the lungs and abdominal organs, causing pain and breathing difficulties. Radiation may help improve these symptoms.
Resources for Mesothelioma Patients
03. Types of Radiation
Types of Radiation Therapy
There are two main types of radiation therapy treatments for mesothelioma, external beam radiation (EBRT) and internal radiation therapy. Benefits and risks are different for each type. Patients should discuss options with their medical team.
External Beam Radiation Therapy (EBRT)
External beam radiation therapy is a non-invasive procedure. EBRT uses intense radiation beams to target malignant mesothelioma tumors. A computer guides the beams. Computer guidance helps the radiation to avoid healthy tissue while targeting cancer cells.
Mesothelioma oncologists may recommend specific forms of EBRT such as 3-D conformal radiation or intensity-modulated radiation.
3-D Conformal Radiation Therapy (3DCRT)
3-D conformal radiation therapy (3DCRT) uses imaging scans to plan and deliver the treatment. Doctors may include CT, MRI or PET scans in this planning process. These scans allow the computer to target beams of radiation that follow the shape of the tumor precisely.
By accurately targeting the tumor, 3DCRT can deliver higher doses of radiation and spare healthy tissue.
Study Spotlight: 3-D Conformal Radiation Therapy for Pleural Mesothelioma
A 2016 study investigated radiotherapy in pleural mesothelioma patients. Doctors prescribed multimodal treatment. The treatment consisted of chemotherapy followed by extrapleural pneumonectomy surgery, then 3DCRT. Of the patients, 17 completed all three treatments, while 13 stopped after surgery.
Researchers found patients who completed all three treatments had the best outcomes. Median survival for patients completing all three treatments was 39.4 months. Median survival for patients who did not undergo radiotherapy was 11.4 months.
In this study, 3DCRT substantially improved survival in pleural mesothelioma.
Intensity-Modulated Radiation Therapy (IMRT)
Intensity-modulated radiation therapy (IMRT) is a form of 3DCRT. Doctors commonly use IMRT for the treatment of pleural mesothelioma. IMRT aims beams of radiation at the tumor tissue from several different directions. However, IMRT uses a larger number of smaller beams versus 3DCRT.
By using more beams, IMRT can vary the strength of each beam. This allows doctors to target higher doses of radiation to certain parts of the tumor. The unique properties of IMRT may allow doctors to more precisely kill cancer while minimizing damage to healthy tissue.
Study Spotlight: Surgery for Malignant Pleural Mesothelioma After Radiotherapy (SMART) Clinical Trial
The SMART study investigated a new way to approach radiotherapy treatment in mesothelioma. Rather than treating patients with radiation after surgery, SMART investigated radiation before surgery.
Over the course of 11 years, 96 eligible patients underwent treatment according to the SMART protocol. All patients had previously untreated pleural mesothelioma and otherwise good health. Patients received a high dose of intensity-modulated radiation to the cancerous side of their chest.
Patients then underwent radical surgery within one week of ending radiation. This surgery consisted of extrapleural pneumonectomy (EPP). EPP removes the lining of the lung (the pleura) and the entire affected lung. EPP may also remove cancerous portions of the diaphragm and pericardium (lining of the heart).
Median overall survival was 24.4 months. However, survival according to cell type was different.
In patients with an epithelioid cell type, median survival reached 42.8 months.
According to experts, the SMART protocol provides good early- and long-term results. However, the protocol is risky. The initial radiation treatment causes severe lung damage, by design. This requires swift surgical removal of the damaged lung.
Overall, the SMART protocol is a technically challenging treatment for doctors and surgeons. The study authors advise the protocol should only be adopted in expert cancer centers with substantial surgical experience.
Source: The Lancet
Stereotactic Body Radiation Therapy (SBRT)
Stereotactic body radiation (SBRT) is an advanced form of IMRT. SBRT uses higher doses of radiation in a smaller number of treatments than IMRT. As such, SBRT requires more precision in planning and delivering the therapy.
According to experts, SBRT may provide several advantages over IMRT. SBRT may be more effective in killing cancer cells and less likely to damage normal tissue. SBRT also requires fewer treatments, potentially making it a more economical therapy.
Study Spotlight: Stereotactic Body Radiation (SBRT) for Pleural Mesothelioma
A recent study investigated SBRT in patients with recurrent pleural mesothelioma. The study included 21 patients, of which 18 had undergone prior pleurectomy/decortication surgery. The other three patients initially received systemic chemotherapy treatment. All study patients had initially responded well to therapy. Some time later, these patients experienced limited cancer recurrence or progression.
Study doctors treated these patients with SBRT. At 12-month follow-up, 75% of the treated tumors had not progressed. Median overall survival was 29 months. Median survival was measured from the time of SBRT treatment, not from the time of diagnosis. Thus, patients in this study achieved remarkable survival.
According to the study authors, this treatment achieved high local control with low toxicity and promising survival.
Source: Frontiers in Oncology
Internal Radiation Therapy
Internal radiation therapy may be called brachytherapy. This type of radiation uses medical implants to deliver cancer-killing energy to tumors. Brachytherapy treats cancer locally, only affecting tissues relatively nearby the implant(s).
Brachytherapy uses seed, ribbon or capsule implants to deliver radiation. These implants may stay in the body indefinitely. The implants may also be removed after a period of time.
According to PubMed, only two medical studies have mentioned brachytherapy and mesothelioma in the last decade. However, other forms of radiation appear frequently in mesothelioma studies. Thus, brachytherapy is rarely used in mesothelioma.
04. Radiation Procedure
The Radiation Procedure and Experience
Each patient’s radiation therapy experience will depend on several factors. The location of treatment, specific type of radiotherapy and patient’s cancer stage can all play a role.
Radiation therapy for mesothelioma often occurs once a day on weekdays. This treatment may take place in a single week. The treatment may also take several weeks.
For example, the EBRT process may include the steps listed below.
External Beam Radiation Therapy (EBRT) Treatment Process
- Planning Session: EBRT requires careful planning. This means the patient will have an appointment or two devoted to this process. The radiation team may call this a marking session. During this time, the patient will lie very still. Radiation specialists will set up pillows or body molds to help the patient maintain the best position. Once situated, a health care provider will use a marker or small tattoo to mark the treatment location. The radiation team will use the patient’s position and tumor information to design the best possible treatment.
- Treatment: The patient will lie on a table in the same position determined in the planning session. The radiation machine, a linear accelerator, may rotate around the patient’s body. During treatment, the machine will make a buzzing sound. The treatment takes about 10 to 30 minutes. Treatment usually occurs once a day for several days in a row. It may last several weeks in total.
Patients receiving SBRT may have a slightly different treatment experience. For instance, SBRT may require fewer treatments than EBRT.
Radiation typically does not cause pain during the treatment. Some people continue working during radiation treatment. However, over time and with additional treatments, patients may no longer feel up to working.
Mesothelioma radiation patients should discuss their recovery process with the cancer team. Treatment team members can help the patient understand their unique situation and what to expect from the recovery process.
Mesothelioma Survival and Prognosis After Radiation
Survival of mesothelioma patients after radiation therapy depends on several factors, including:
- Mesothelioma cell type
- Overall patient health
- Stage of mesothelioma
- Type of mesothelioma
- Radiotherapy treatment type
Radiation is not commonly used for the treatment of peritoneal mesothelioma. In other forms of mesothelioma, survival after radiation therapy ranges from about two years to more than ten years.
Survival of Mesothelioma Patients Treated With Radiation Therapy
- Treatment: Chemotherapy followed by extrapleural pneumonectomy, then radiation therapy
- Median Survival: 39.4 months
- Treatment: Cytoreductive surgery plus radiation therapy
- Median Survival: 8 months
- Treatment: Surgery followed by three years of intermittent chemotherapy, then radiation
- Progression-Free Survival: 50 months
- Treatment: Surgery plus radiation with or without chemotherapy
- Progression-Free Survival: Up to 155 months
Patients should discuss their mesothelioma prognosis with members of their treatment team. Mesothelioma specialists can help patients understand their unique situation and expected survival.
06. Side Effects
Side Effects of Radiation for Mesothelioma Patients
All cancer treatments have side effects, including mesothelioma radiation therapy. However, radiation is a local treatment. This means it does not have the same type of whole-body effects as a systemic cancer treatment such as chemotherapy.
Patients should discuss all potential side effects with their physician. Patients should report any side effects that arise during the treatment process.
Common Side Effects of Radiation Therapy
- Fatigue: Many patients report loss of energy and extreme fatigue following radiation treatments. This fatigue can also last for months after treatment has concluded.
- Hair loss: Patients may experience bodily hair loss at the area of radiation application.
- Mouth problems: When undergoing radiation to the head or neck, patients have reported several oral symptoms. Dry mouth, inflammation in the mouth and lack of taste have all been reported.
- Skin problems: Redness, dryness, peeling and darkening of the skin are common after radiation.
Skin problems associated with radiation treatment may be called radiation dermatitis. These side effects usually go away after treatment ends. In the meantime, patients may find it helpful to treat their skin gently. This could include wearing soft, loose clothing and protecting the affected skin from the sun.
Experts also recommend patients get plenty of rest during radiation treatment. This can help with some of the fatigue that occurs as the body tries to heal after treatment.
Patients should discuss ways to manage their specific side effects with the cancer team.
Who Is Eligible for Mesothelioma Radiation Therapy?
Eligibility of mesothelioma patients for radiation depends on a number of factors, including:
- Mesothelioma stage at diagnosis
- Overall patient health
- Tumor location
Mesothelioma specialists will consider these factors when deciding which, if any, form of radiation to recommend. Patients considering radiation therapy for mesothelioma should consult with an experienced oncologist. Their doctor can explain potential benefits and side effects of radiation treatment.