Intensity-Modulated Radiation Therapy (IMRT)

Intensity-modulated radiation therapy (IMRT) is a form of external-beam radiation in which computer-controlled beams of varying strength shape the dose closely around the target. In mesothelioma, it can treat the lining of one side of the chest after surgery while limiting the dose to the heart, the remaining lung and other organs.

Origin

IMRT developed in the 1990s, as computer planning and multileaf collimators, devices with movable metal leaves that shape the beam, allowed beam intensity to vary across each field. Mesothelioma centers began using it in the early 2000s for radiation to the whole side of the chest after extrapleural pneumonectomy (EPP).

Significance in Asbestos Context

After EPP, when the whole lung on one side has been removed, IMRT can deliver radiation to the entire hemithorax; early experience showed that the dose to the other lung must be tightly limited, because fatal pneumonitis occurred in some patients. After pleurectomy-decortication (P/D) the lung remains, which makes radiation harder, but some centers use hemithoracic pleural IMRT after lung-sparing surgery, and trials have tested it. IMRT is also used to relieve pain from tumor growing into the chest wall, and widely in lung cancer care. Whether radiation is recommended after surgery for mesothelioma varies by center and by patient, and randomized evidence is limited, which is one reason a second opinion at a mesothelioma center can help. Side effects include fatigue, skin irritation, painful swallowing and pneumonitis. Treatment records should name the technique, dose and dates.

Example Sentence

Six weeks after his pleurectomy-decortication, he began five weeks of hemithoracic IMRT at the mesothelioma center, with daily treatments planned to spare his remaining lung.

Related Terms

Extrapleural Pneumonectomy (EPP), Pleurectomy-Decortication (P-D), Intraoperative Radiation Therapy (IORT), Pneumonitis, Proton Therapy, Stereotactic Body Radiation Therapy (SBRT), Mesothelioma Specialist, Second Opinion

Notes

• Ask whether radiation is meant to control the cancer or to relieve pain; the plan and goals differ.
• Ask the radiation team which side effects to report and when they usually appear.
• Keep the radiation treatment summary, which lists the dose, dates and areas treated.