New Research Says IMRT Offers Safer, More Effective Way to Treat Pleural Mesothelioma
Radiation therapy is a conventional treatment for all types of cancer. Also called “radiotherapy,” the treatment uses high-energy x-rays or particles to kill cancer cells. It works by damaging cancer cells’ DNA directly or by creating changed particles (free radicals) within the cells that can in turn damage DNA. Per the National Cancer Institute (NCI), “cancer cells whose DNA is damaged beyond repair stop dividing or die. When the damaged cells die, they are broken down and eliminated by the body’s natural processes.”
Unfortunately, radiation therapy can also damage normal cells, leading to early (acute) and late (chronic) side effects. Acute side effects “occur during treatment, and chronic side effects occur months or even years after treatment ends,” says NCI NIH. Acute side effects may include “skin irritation or damage at regions exposed to the radiation beams. Examples include damage to the salivary glands or hair loss when the head or neck area is treated, or urinary problems when the lower abdomen is treated.”
Fatigue is another side effect, regardless of treatment area, and nausea (with or without vomiting) may occur when the abdomen or brain is treated. Late side effects can include fibrosis (the replacement of normal tissue with scar tissue, leading to restricted movement of the affected area), damage to the bowels, causing diarrhea and bleeding, memory loss, infertility (inability to have a child), and rarely, a second cancer caused by radiation exposure.
Despite potential side effects, mesothelioma can be treated with radiation therapy. However, they are often difficult to treat with this conventional therapy, as mesotheliomas don’t usually grow as single, distinct tumors. Per the American Cancer Society, “it can be hard to aim radiation at them while avoiding nearby normal tissues.” However, “new radiation therapy techniques may make this form of treatment more useful.”
According to a number of recent studies, one newer form of radiation therapy called intensity-modulated radiotherapy (IMRT) may be better and safer than external beam (conformal) radiation therapy. In the book, Intensity-Modulated Radiation Therapy, authors Michael D. Mills and Shiao Y. Woo wrote, "a number of clinical studies have demonstrated superior dose distributions with IMRT compared to conventional radiation therapy. An important corollary is the reduced acute radiation toxicity as a result of normal tissue avoidance and ability to perform dose escalation. Within the past 25 years, this concept has progressed from theory to prototype delivery systems to wide and universal acceptance of IMRT as a necessary standard of good radiotherapy delivery practice.”
In a recent study, researchers evaluated twenty-four radiation therapy plannings in malignant mesothelioma patients, and compared them with dosimetric outcomes of conformal radiation therapy and IMRT. Per the study, “hemithoracal radiation therapy was performed on 12 patients with a fraction of 1.8 Gy to a total dose of 50.4 Gy. All organs at risk were contoured. Radiotherapy plannings were differed according to the technique; conformal radiation therapy was planned with conventionally combined photon–electron fields, and intensity-modulated radiation therapy was planned with 7 to 9 radiation beam angles optimized in inverse planning. Strict dose–volume constraints were applied.” The research team discovered that IMRT was “statistically superior in target coverage and dose homogeneity.” In conclusion, the team wrote, “with a complex and large target volume of malignant pleural mesothelioma, intensity-modulated radiation therapy has the ability to deliver efficient tumoricidal radiation dose within the safe dose limits of the remaining lung tissue.” Simply put, IMRT was found to be both less harmful and more effective.
Another news source reports that researchers in Texas and New York found that mesothelioma patients who had IMRT after pleurectomy/decortication (P/D) surgery or extrapleural pneumonectomy (EPP) lived longer than most people did with the disease. This is all promising news for the future of IMRT as a safer and more effective treatment for mesothelioma.
If you have been diagnosed with mesothelioma, talk to your doctor about innovative, newer treatments such as IMRT. When combined with conventional treatments such as surgery and chemotherapy, IMRT could improve your quality of life and help you live longer.
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Ulger, Sukran, Eren Cetin, and Serap Catli. "Intensity-Modulated Radiation Therapy Improves the Target Coverage Over 3-D Planning While Meeting Lung Tolerance Doses for All Patients With Malignant Pleural Mesothelioma." Technology in Cancer Research & Treatment 16.3 (2016): 332-38. SAGE Journals. Web. 7 Aug. 2017.
Woo, Shiao Y. "History of IMRT." Intensity-Modulated Radiation Therapy. By Michael D. Mills. Japan: Springer, 2015. 3-14. Print.