Three-Dimensional Radiation
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Three-dimensional radiation therapy is a type of radiotherapy and potential treatment for mesothelioma and other types of cancer. This advanced therapy uses a 3D image of the tumor to better target the radiation and avoids damage to healthy cells.
Radiation with an External Beam
There are two broad categories of radiation therapy for cancer patients:
- 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 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 the 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.
- 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, inside the body.[1]
What Is Three-Dimensional Conformational Radiation Therapy?
Three-dimensional conformational radiation therapy (3DCRT) is a type of external beam radiation. It uses images from scans to create a three-dimensional model of a tumor and the surrounding tissue.
With this three-dimensional picture, the oncologist can conform the external beam of radiation can to the shape of the tumor.
This allows doctors to dose a patient with radiation directed more at the tumor and less at the surrounding healthy tissue.[2] Specially molded blocks placed around the patient during treatment can also help focus the radiation.
The Procedure
3DCRT begins with several imaging scans, usually CT scans, although PET scans and MRIs may also be used. The scans image the area of the body to be treated, such as the chest cavity for patients with pleural mesothelioma.
Doctors put 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 radiation oncologist can selectively modulate the radiation beam’s intensity, dose, and direction so that it avoids healthy tissue and conforms to the shape of the tumor.
For the patient, going through 3DCRT means spending extra time being in a 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 to 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 fifteen and thirty 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.
IMRT
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.
Oncologists increasingly use IMRT 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.[3]
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. It may be too risky to use radiation close to a vital organ with traditional radiation treatment, but with 3DCRT, the risks of hitting the heart with radiation are lowered.
Risks
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. There may be more risks of side effects for pleural mesothelioma patients 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 will likely 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 in clinical trials, speak with your radiation oncologist to determine the next best steps.
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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.