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Radiation therapy is one of three main types of treatment for mesothelioma and other types of cancer. The procedure involves using high-energy radiation to kill cancer cells. There are risks and benefits to this procedure because the radiation kills all cells indiscriminately, cancer and healthy cells alike. Advances in how radiation is dosed and applied to tumors have reduced the risk of killing healthy cells and made the procedure safer. One of these is three-dimensional conformational radiation therapy, or 3DCRT. It is often used along with surgery and chemotherapy for a complete approach to reducing tumors and treating cancer.
Radiation with an External Beam
There are two broad categories of radiation therapy for cancer patients: external beam and brachytherapy. Brachytherapy involves implanting a small device inside the body, either within a tumor or next to it. The device emits radiation and targets a small area. In other words, the radiation is applied internally, or inside the body.
External beam radiation therapy is the most common kind of radiation done for mesothelioma patients and other types of cancer patients. A beam of radiation outside of the body is aimed at the part of the body where the tumor is located. To get to the tumor the beam has to penetrate skin and other healthy tissues. This can cause side effects and damage to healthy parts of the body. However, the risks of this damage are often worth the benefits of shrinking the tumor with radiation.
What is Three-Dimensional Conformational Radiation Therapy?
Three-Dimensional Conformational Radiation Therapy (3DCRT) is a type of external beam radiation. It is an advanced type of this procedure that involves the use of images from scans to create a three-dimensional model of a tumor and the surrounding tissue. With this three-dimensional picture, the external beam of radiation can be conformed to the shape of the tumor. This allows doctors to dose a patient with radiation that is directed less at the healthy tissue around the tumor and more directed at it. Specially molded blocks placed around the patient during treatment can also help to focus the radiation.
3DCRT begins with making several imaging scans, usually CT scans, although PET scans and MRIs may also be used. The scans are used to image the area of the body to be treated, such as the chest cavity for patients with pleural mesothelioma. The images are put into a software program so that a computer can take the two-dimensional images and turn them into a three-dimensional model of the tumor and the healthy tissues around it.
Using the three-dimensional model, the computer, the radiation oncologist can selectively modulate the intensity, dose, and direction of the radiation beam so that it avoids healthy tissue and conforms to the shape of the tumor. The program for the treatment and beam is inputted into the computer that will deliver the treatment to the patient.
For the patient, going through 3DCRT means spending extra time being scanner and treated as compared to traditional external beam radiation therapy. The patient will be examined by a radiation oncologist and other medical team members so they can develop a treatment plan. The patient then must go through several imaging scans, which can take up to a couple of hours.
Once the scans have been done, the medical team needs up to a week to create the individualized 3DCRT treatment plan. Once this is all done, the patient will only need to spend between 15 and 30 minutes sitting still or lying down while the computer delivers the radiation therapy in a special treatment room. The actual treatment is painless. This may be done several times over the course of a few days.
Intensity-modulated radiation therapy, or IMRT, is an even more advanced form of 3DCRT that modulates the intensity of radiation beams. While still avoiding healthy tissues, it allows for higher doses of radiation to be targeted at the tumor. IMRT has been increasingly used to treat patients with pleural mesothelioma, especially after surgery to remove the bulk of tumors in the chest cavity. Initial studies have found that this radiation therapy can help control mesothelioma growth and recurrence better than other types of radiation treatment.
Benefits of 3DCRT
The main benefit of using 3DCRT to treat cancer is that it reduces the amount of radiation delivered to healthy tissues and focuses more of the radiation on the tumor and cancer cells. Because this is a more focused and specific type of radiation therapy, it can be used on tumors that previously would have been considered too close to important organs to be treated with radiation. For instance, 3DCRT can be used to focus radiation on a mesothelioma tumor that is close to the heart. With traditional radiation treatment, it may be too risky to use radiation that close to a vital organ, but with 3DCRT the risks of hitting the heart with radiation are lowered.
There are fewer risks and side effects with 3DCRT as compared to traditional radiation therapy. In fact some patients don’t experience any adverse effects from this treatment. Most common are minor side effects to the area of the body being treated, such as skin irritation, hair loss, and rashes at the site on which the beam is focused. For pleural mesothelioma patients there may be more risks of side effects because the radiation is close to important organs, like the lungs.
Pneumonitis, for instance, or inflammation of the lungs is possible. It causes shortness of breath and coughing and is usually temporary, but for some people causes lasting damage. Radiation to the chest cavity can also cause inflammation in the mucosal lining of the esophagus and the throat and mouth.
Three-dimensional radiation therapy is a new, advanced technique for delivering radiation therapy that is more targeted and that harms fewer healthy cells in the body. For patients with mesothelioma, this provides an exciting new way to get an effective treatment, especially because the tumors are so close to vital organs like the heart and lungs. As research continues, there are likely to be even more advances that make radiation treatment an even more viable and safe option for cancer patients. Clinical trials may also include new methods or doses of radiation. If you are interested clinical trials, speak with your radiation oncologist to determine the next best steps.
Page Medically Reviewed and Edited by Anne Courtney, AOCNP, DNP
Anne Courtney has a Doctor of Nursing Practice degree and is an Advanced Oncology Certified Nurse Practitioner. She has years of oncology experience working with patients with malignant mesothelioma, as well as other types of cancer. Dr. Courtney currently works at University of Texas LIVESTRONG Cancer Institutes.