Radiation Therapy for Pleural Mesothelioma
Radiation therapy (RT) can relieve pain in people with pleural mesothelioma. Though early research wasn’t promising, recent studies are showing extended survival in patients treated with modern forms of precise radiation therapy before or after surgery. Radiation therapy alone cannot cure pleural mesothelioma, but it can offer pain relief and may prevent spreading of cancerous cells to incisions made for biopsies and surgical procedures. Radiation therapy is often a part of a multimodal treatment plan.
The treatment is relatively common for pleural mesothelioma. A specialist known as a radiologist applies ionizing radiation to the tumor area. The application is not painful. The therapy works by directly killing cancer cells and by damaging DNA that causes the formation of cancer cells. The therapy works by damaging DNA that causes the growth and replication of cancer cells.
Pleural tumors that invade the chest wall can become painful as they grow. Radiation therapy can shrink these tumors and reduce pain in many cases. Following surgery, using RT as an adjuvant therapy (a therapy that enhances the effectiveness of overall treatment) has helped doctors kill remaining cancer cells.
Current Roles in Treatment
The current roles of radiation therapy in pleural mesothelioma treatment include:
- Palliative pain relief
- Adjuvant therapy after surgery
- Seeding prevention
Palliative Pain Relief
Radiation therapy may offer pain relief for patients with tumors that reach the chest wall or lymph nodes, according to the European Respiratory Society and the European Society of Thoracic Surgeons. Other sources of pain may not respond to radiation therapy. One mesothelioma study reported that 50 percent of participants experienced relief from pain associated with a pleural mesothelioma symptom, including dyspnea (shortness of breath), Pancoast’s syndrome (pain in the shoulder, arm and hand), and superior vena cava obstruction when treated with radiation therapy. Short courses of radiation therapy are used to regulate pain, as opposed to long courses that have a more aggressive intent.
Sometimes doctors use radiation therapy for pain relief as part of a management plan that treats pleural mesothelioma as if it were a chronic illness. For example, pleural mesothelioma survivor Judy Glezinski had surgeries in 1990 and 1997 to remove tumors from around her lungs. Several years after her last surgery, doctors used radiation therapy to treat a specific area that was causing Judy pain. She was relatively pain-free for one year after receiving radiation therapy.
Adjuvant Therapy after Surgery
Expert opinion on the value of post-operative radiation therapy for PM varies because some surgical procedures have lasting effects on the ability to administer radiation. For example, because an extrapleural pneumonectomy removes one lung, aggressive RT can be administered to the area where the lung was located without endangering the remaining lung.
Conversely, aggressive radiation following a pleurectomy/decortication, a surgery that preserves the affected lung, requires more precise delivery of radiation because the amount of radiation required to effectively treat tumors is often damaging to lung tissue. Several studies report that intensity-modulated radiation therapy (IMRT) can safely administer high doses of radiation following a pleurectomy/decortication (P/D). One study on IMRT in mesothelioma patients who underwent a P/D reported a median survival of 26 months (average survival rate is around 12 months).
It is relatively common for pleural mesothelioma cells to spread along thoracentesis tracts, biopsy tracts, chest tube sites and surgical incisions. Once the cancerous cells spread, a process known as seeding, they can form small tumors called nodules. Seeding may occur in 20 to 50 percent of mesothelioma patients who undergo such procedures.
In an attempt to prevent spreading, doctors can radiate the incision and drainage sites in the weeks following the procedures. Studies to test the value of RT to prevent seeding (known as prophylactic radiation) have mixed results.
Some studies report that radiation effectively prevents seeding, and others find little to no support for the treatment. A 1995 study (involving 20 patients who received prophylactic radiation and 20 patients who did not receive any RT) reported that no patients in the radiated group developed tumor nodules, while eight in the untreated group developed such nodules. A 2007 study of 61 patients, half of which received prophylactic radiation, reported that eight in the RT group developed nodules, while four in the untreated group developed nodules. Of the 12 nodules that developed, only three were reported as painful.
Experts suggest that inconsistent radiation therapy techniques could explain the mixed results. Some European researchers believe that prophylactic radiation should only be performed if a patient develops painful tumor nodules. In an exemplary case report, a 71-year old PM patient developed a tumor along a chest drain site even after receiving prophylactic radiation. Doctors re-treated the site with RT, and complete resolution of the tumor was reported with no recurrence.
Types of Radiation for Pleural Mesothelioma
Radiologists use two forms of RT to treat pleural mesothelioma: brachytherapy and external beam radiation therapy.
Though not as commonly used as other forms of RT for pleural mesothelioma, brachytherapy is used in some cases. Researchers are still studying the value of brachytherapy in clinical trials. In this form of RT, a radioactive object is placed in or near the tumor. The object emits a small field of radiation intended to directly target the tumor. The radiation damages the tumor’s cancerous cells in ways that promote cell death, leading to tumor shrinkage.
The radioactive object can be placed permanently or temporarily. Permanent placement is more common for PM, and the object will release radioactive waves for only a few months in most cases. Tiny seeds filled with radioactive material are placed directly into tumors with a needle or other medical device. Imaging may be used during and after placement to ensure the seeds are correctly implanted in the tumor. The seeds are coated with a nonradioactive metal to ensure the material inside never leaks. The seeds may set off metal detectors permanently and could alert radiation detectors for several weeks or months after placement.
High-dose surface brachytherapy, where a radioactive object is laid on the skin near the tumor(s), is a temporary form of brachytherapy used in some PM cases to prevent tumor seeding along incisions following surgery. A radioactive applicator is placed directly on surgical incisions and delivers focused radiation to prevent spread of cancerous cells to the incisions. Length of treatment will vary by patient and may require an overnight hospital stay.
Permanent brachytherapy is often performed on an outpatient basis and continues to work for weeks or months while the patient goes about their life. Temporary brachytherapy may take up more of the patient’s time for application, but they don’t have to think about a radioactive object residing in their body. Both forms of brachytherapy are affective at killing cancerous cells, but neither can cure pleural mesothelioma. Brachytherapy is used in conjunction with other treatments to more aggressively attack the cancer than using one therapy alone.
External Beam Radiation Therapy
Instead of applying radiation with an object that is placed in or on the tumor, in this approach the radiation is delivered externally from a machine using a radioactive beam. The treatment itself is painless, but may later cause skin irritation that feels like sunburn.
During an initial consultation patients learn about the procedure, how it is performed and what they’ll need to do prepare and recover. Patients will also have to sign an informed consent form acknowledging the inherent risks of radiation therapy. Before the therapy is administered an imaging simulation appointment will take place to determine the position in which the patient will receive future treatment. Small markers will be placed on the patient’s body to ensure accuracy of positioning for treatment. These markers may be permanent tattoos or colored ink that eventually fades away. During the simulation detailed imagery is collected to plan where the radiation beams will be directed to treat tumors. Various props are configured to help the patient remain comfortable in the position during future treatment.
The treatment itself is painless. Patients may hear the machine making sounds during treatment or see the beam applicator moving. Therapy is most often given once a day, five days a week for several weeks. Treatment appointments last about an hour and most of the time is spent ensuring the patient is positioned properly. Beams of radiation may be administered for only a few minutes each session, which can vary depending upon the type of external beam radiation applied.
There are two types of external beam radiation, and the difference lies in the intensity of the radiation delivered.
Three-Dimensional Conformal Radiation Therapy
Detailed imaging scans help radiologists to tailor the radiation dose in three-dimensional conformal radiation therapy (3D-CRT). After collecting 3D images of the pleural tumors, a customized plan is devised to deliver radiation using fixed beams. The intensity of the radiation beam is uniform when delivered to the tumor. Careful planning with the help of detailed imaging helps prevent healthy tissue from receiving as much radiation as the tumors.
Intensity-Modulated Radiation Therapy
Much like 3D-CRT, intensity-modulated radiation therapy (IMRT) uses 3D images of pleural tumors to deliver radiation. IMRT is different because the radiation intensity is modulated — or controlled — to administer varying levels of radiation across the targeted area from different beam directions. Higher-intensity radiation can be delivered directly to the tumor with minimal harm to nearby healthy tissue.
What to Expect
Prior to treatment, patients will receive instruction from a doctor or nurse on what to do before receiving radiation therapy. Sometimes patients are asked to follow certain bowel and bladder preparation regimens. Imaging scans are taken before radiation is delivered, often with computed tomography (CT) or magnetic resonance imaging (MRI) scans.
In some cases certain chemicals will be used in combination with radiation therapy to make cancer cells more susceptible to radiation (radiosensitizers) or to protect healthy cells from damage (radioprotectors). Many of these chemicals are man-made drugs, such as the chemotherapy drug gemcitabine, which is used as a radiosensitizer. A few natural chemicals act as radiation sensitizers or protectors, such as curcumin, a compound found in the Indian spice turmeric. Be sure to tell your doctor if you are taking any supplements prior to treatment.
Radiation therapy can cause early and late side effects. Early side effects occur during or right after treatment. The most common early side effects are fatigue and skin problems. Skin around the area receiving radiation may become red, irritated, sensitive, swollen, dry or itchy, and may peel or blister.
Late side effects typically occur months or years after radiation therapy is completed. Although rare, late side effects are sometimes permanent. Lung tissue scarring or fibrosis may develop in the months following RT, and nearby lymph nodes may become calcified in some cases.
Other early and late side effects of radiation therapy for pleural mesothelioma include:
|Early Side Effects||Late Side Effects|
|Skin burns near application area||Radiation pneumonitis|
|Hair loss around treatment area||Pleural effusion|
|Feeling tired||Liver radiation damage|
|Esophagitis||Cardiac radiation damage|
Not everyone with pleural mesothelioma will experience the same side effects. The number and severity of side effects depend on the dose and type of radiation received, as well as where the radiation is applied on the body.
Some people with pleural mesothelioma use complementary and alternative medicine to cope with mild side effects of traditional cancer treatment.
Though radiation therapy alone cannot cure pleural mesothelioma, it can play a role in a multimodal treatment plan. Radiation therapy can reduce pain for people with pleural mesothelioma, and may be used to prevent or treat tumor seeding. Advances in radiology are improving radiation therapy options for those with pleural mesothelioma, making the therapy more accurate and effective against pleural mesothelioma tumors.