A team of researchers from the Princess Margaret Cancer Centre in Toronto has learned that using non-ablative hypofractionated hemithoracic radiation for mesothelioma can help improve the outcomes for patients with pleural mesothelioma.

What Is Non-Ablative Hypofractionated Hemithoracic Radiation?

In radiation therapy, the dosage of radiation is divided into parts that are called fractions. In normofractionated radiotherapy, which is the current standard of care, patients are given 2 grays (Gy) of radiatiq2on per fraction. A gray is a measurement of how much energy a piece of tissue will absorb, with 1 Gy being equal to 1 joule per kilogram or 100 rad.

Hypofractionated is when the radiologist gives the patient more of the dosage in each fraction. So instead of getting only 2 Gy at a time, the patients will receive 3 or more Gy at once. Currently, researchers aren’t sure what dosage or division of that dosage is the best amount to give patients.

The other two terms in the name mean that the radiation doesn’t destroy healthy tissue (non-ablative) and that it’s localized to one side of the patient’s chest (hemithoracic). Non-ablative radiation is also called Stereostatic Ablative Radiotherapy (SABR), a highly accurate radiation treatment that precisely targets tumors and avoids destroying nearby healthy tissues.

Benefits of Non-Ablative Hypofractionated Hemithoracic Radiation for Mesothelioma

There are several benefits of hypofractionated radiation for mesothelioma:

  • It’s faster. Unlike the current form of radiation, hypofractionated radiotherapy can be done over a few days instead of weeks.
  • It can be given to the patient before, during or after surgery.
  • It’s a more effective form of pain relief than normofractionated.
  • It can help prevent the spread of cancer at surgical incision sites.
  • It may activate the patient’s immune system, which potentially sets this type of treatment up to be effectively partnered with immunotherapy

Current Setbacks

Unfortunately, as with any new potential treatment, there are a few setbacks that scientists will have to overcome before non-ablative hypofractionated hemithoracic radiation for mesothelioma can replace the current standard of care. One of the current problems is finding the correct dosage and fractions to use.

Another problem is the negative impact hypofractionated radiation can have on a patient’s immune system, which seems odd since one of the benefits of this therapy is that it encourages the immune system to attack the tumor. However, non-ablative hypofractionated hemithoracic radiation leads to an increase of t-cells (white blood cells that mature in the thymus) in the tumor.

Unfortunately, these t-cells are immunosuppressive, which means they tell the body’s immune system to stop attacking the tumor. However, this problem can potentially be overcome by also treating the patient with immunotherapies that target the t-cells in mesothelioma. Other researchers are already looking into ways to reprogram t-cells.

Becoming a New Standard of Care

The standard of care is the treatment course most doctors will recommend. It is also the bar that new treatments have to meet and surpass to be made widely available to patients. Some of the criteria new treatments have to meet to become the new standard of care is that they have to show they are safer, more effective, or have fewer or less harmful side effects.

In order to do this, new treatments have to pass through several phases of trials. The preclinical trial where the results are studied in labs. Phase 1 where it’s only made available to a few people so researchers can determine what the best dosage is, and Phases 2 through 4 where the researchers focus on finding out how well the drug works and whether or not it stays safe for the patients to use over increasingly longer periods of time.

So, for non-ablative hypofractionated hemithoracic radiation to become the new standard of care, researchers will have to overcome their current problems. That is, they will need to find the best dosage and fractions to give patients, as well as an effective form of immunotherapy to counteract the increased amounts of immunosuppressive t-cells.

But, if everything goes well, treatment for mesothelioma patients will be faster and more effective.

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Sources
  1. De Perrot, M. & Cho, J. (2018). “Non-ablative hypofractionated hemithoracic radiation—a new standard of care in mesothelioma?” Journal of Thoracic Disease. Retrieved from: http://jtd.amegroups.com/article/view/24538/pdf. Accessed October 15, 2018.
  2. Health Physics Society. “Gray (Gy).” Retrieved from: http://hps.org/publicinformation/radterms/radfact79.html. Accessed October 17, 2018.
  3. Stanford Health Care, “Stereotactic Ablative Radiotherapy (SABR/SBRT)”. Retrieved from: https://stanfordhealthcare.org/medical-treatments/s/stereotactic-body-radiation-therapy.html. Accessed on, October 18, 2018.
  4. Mesothelioma Help Now. “Mesothelioma Clinical Trial Phases 0-4.” Retrieved from https://www.mesotheliomahelpnow.com/treatment/clinical-trials/phases/. Accessed October 17, 2018.

Last modified: October 24, 2018