Radiation Therapy for Malignant Pleural Mesothelioma

Overview

Radiation therapy uses high-energy rays to damage or kill cancer cells by preventing them from growing and dividing. Similar to surgery, radiation therapy is a local treatment used to eliminate or eradicate cancer in a defined area. Radiation therapy is not typically useful in eradicating cancer cells that have already spread to other parts of the body. Radiation may be used to cure or control cancer, or to ease some of the symptoms caused by cancer. Visit the Radiation Therapy Center for in-depth information on how radiation therapy is delivered, common side effects and answers to frequently asked questions. The following information discusses the role of radiation therapy in the management of mesothelioma.

Since malignant mesothelioma spreads widely throughout the pleura and adjacent lung, it is generally impossible to administer the doses of radiation necessary to kill all of the cancer without severely damaging normal tissues and causing significant side effects. In the treatment of malignant mesothelioma, radiation therapy is typically administered:

• In addition to surgery for patients with stage I-III disease (adjuvant radiation)
• In addition to surgery and chemotherapy for patients with stage I-III disease (adjuvant radiation and chemotherapy)
• To reduce (palliate) the signs and symptoms of the cancer in patients with stage IV disease (radiation for palliation).

Radiation Therapy Delivery

Radiation therapy is delivered to the site of mesothelioma from a machine outside the body, a technique that is called external beam radiation therapy (EBRT). Treatments are typically given daily over a 5-6 week period and additional concentrated radiation treatment, called a boost, may be given directly to a smaller area where the cancer was found.

Adjuvant Radiation Therapy

Adjuvant therapy is therapy given following surgical treatment. Adjuvant radiation therapy may be given to patients with stage I-III disease at high-risk for relapse.  Researchers from Memorial Sloan-Kettering Cancer Center have shown that adjuvant radiation therapy can dramatically reduce the rate of local cancer recurrence in patients with malignant mesothelioma.  In their study, adjuvant radiation improved the survival of patients with early-stage disease.^[1]

Adjuvant Radiation and Chemotherapy

The lack of any single consistently curative treatment for malignant pleural mesothelioma has led to the development of multi-modality therapy, including surgery, radiation therapy, and chemotherapy. When radiation and chemotherapy are administered after surgery, they are called adjuvant therapies. Research suggests that patients in good condition with stage I-III malignant pleural mesothelioma should be treated with adjuvant chemotherapy and radiation therapy.

Researchers from the Dana Farber Cancer Center in Boston, MA have reported that among 120 patients with malignant pleural mesothelioma who underwent surgery with extrapleural pneumonectomy and adjuvant treatment with chemotherapy, and radiotherapy, 22% survived 5 years or longer. Patients with epithelial type cancer and those with no lymph node involvement lived longest (Table 1).  On average, patients with stage I disease survived 22 months, compared to 17 months for stage II disease and 11 months for stage III disease.^[2]

Table 1 Survival of patients treated with surgery, radiation, and chemotherapy

Italian researchers have also reported that 21 of 27 patients with stage I-III malignant pleural mesothelioma treated with surgery followed by adjuvant chemotherapy and radiation therapy, survived more than a year after treatment.^[3]

Radiation for Palliation

Because mesothelioma is sensitive to radiation therapy it can be used to treat local areas of cancer with the intent of reducing symptoms caused by the cancer.^[4] Administration of radiation therapy in order to reduce pain, improve breathing, or relieve other side effects caused by the cancer is referred to as palliation.

Side Effects of Radiation Therapy

One of the problems with radiation therapy for malignant pleural mesothelioma is that the cancer is usually widespread, requiring a large area to be radiated. The high doses of radiation necessary for eradication of disease may cause sunburn like changes to the skin, fatigue, and damage normal structures in the chest. Complications of radiation therapy for malignant pleural mesothelioma include inflammation of the lungs (pneumonitis), inflammation of the sack around the heart (pericarditis), and compression of the heart (cardiac tamponade).^[5]

Strategies to Improve Treatment

The development of more effective cancer treatments requires that new and innovative therapies be evaluated with cancer patients. Clinical trials are studies that evaluate the effectiveness of new drugs or treatment strategies. Future progress in the treatment of malignant pleural mesothelioma will result from the continued evaluation of new treatments in clinical trials. Participation in a clinical trial may offer patients access to better treatments and advance the existing knowledge about treatment of this cancer. Patients who are interested in participating in a clinical trial should discuss the risks and benefits of clinical trials with their physician. Areas of active exploration to improve the treatment of malignant pleural mesothelioma include the following:

Newer radiation techniques: Radiation therapy can be delivered more precisely to the areas of pleural involvement with a technique called intensity modulated radiation therapy (IMRT).^[6] This technique combines all of the features of three-dimensional conformal radiation therapy, or 3D-CRT plus the ability to direct the dose to the cancer and reduce the amount delivered to normal tissue. IMRT appears to reduce the chance of injury to nearby body structures, such as the lung and heart.  Since IMRT can better target the area of cancer, radiation oncologists are evaluating whether higher doses of radiation can be given safely in order to improve the chance of cure.

Researchers from MD Anderson Cancer Center have reported that IMRT after extrapleural pneumonectomy is a promising approach that improved local control of the cancer. Approximately 9 months after treatment, they reported no local recurrences for the 28 patients in the study. However, spread to distant locations in the body, called systemic metastasis, became more frequent.^[7]

Managing Side Effects (Supportive Care): Supportive care is treatment designed to prevent or control the side effects of cancer and its treatment. Side effects not only cause patients discomfort, but also may prevent the delivery of therapy at its planned dose and schedule. In order to achieve optimal outcomes from treatment and improve quality of life, it is imperative that treatment be delivered as planned and that side effects resulting from cancer and its treatment are appropriately managed. For more information, visit  Managing Side Effects.

References

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