Definition and Overview
3D conformal radiotherapy is a type of cancer treatment that uses radiation beams the same shape as the tumor. This is an improvement over previous radiotherapy technology wherein the beams only matched the height and width of the tumor, thus exposing some healthy tissues to the radiation. Like intensity-modulated radiation therapy or IMRT, this treatment is a more precise option for those suffering from cancerous tumors, thus reducing the potential side effects.
Who Should Undergo and Expected Results
Due to three-dimensional conformal radiotherapy’s ability to conform to the exact shape of the tumor, this variation from the standard radiotherapy is a highly beneficial treatment option for patients whose tumors are irregular in shape. It is a safer option for patients with tumors that are positioned very close to healthy organs and tissues or in cases where the position of the tumors means that a lot of healthy tissues will be affected. Records show that this radiotherapy technique is most commonly used for cancer tumors affecting the brain, lung, liver, and prostate. It is also the more favorable treatment for head and neck cancers, taking into consideration their sensitive location.
By using 3D conformal radiotherapy in such cases, the healthy tissues and nearby organs will be spared from the effects of the treatment, reducing the negative side effects in the process.
Furthermore, due to the safety of healthy tissues, oncologists are able to increase the doses of radiation, increasing the chances of success, while side effects are kept minimal. This treatment has indeed shown an improvement in the rate at which tumors are shrunk and destroyed, thanks to the higher levels of radiation delivered at each session.
How is the Procedure Performed?
3D conformal radiation therapy begins with detailed imaging tests to get an exact view of the tumor and determine its location, size, and shape. These tests may include ultrasound, computed tomography or CT scans, magnetic resonance imaging or MRI, and positron emission tomography or PET scans.
Once the tumor’s exact contour is determined, the treatment then uses a special 3D technology called a “multi-leaf collimator” to sculpt the radiation beam to an exact shape. Once the radiation beams are shaped and their numbers determined, the oncologists set the dose of each beam to match the goals of each stage of the treatment. The details of treatment, i.e. how many sessions are required and how much radiation should be delivered at each session, is determined by the size and stage of the tumor.
Since the same radiation beams are used in each session, the patient will be asked to lie down in the exact same position every time. In some cases, patients are also given small freckle-sized tattoos to serve as positioning markers. Now, however, to help ensure correct positioning in every session, a special body mold that is custom-fit to the patient is also being used. Thus, patients have to wait until their individual body mold is prepared before they can begin treatment. These positioning requirements, which are not as critical in standard radiation therapy, are a must in 3D conformal treatments.
Once the patient is properly and safely positioned, the radiation delivery system starts to deliver radiation beams toward the tumor, moving in a circular motion and sending the beams from different angles. Patients do not feel any pain throughout the entire process, making sedation unnecessary. Each session will take only around 30 minutes, performed once daily for up to seven weeks. If the treatment goals are not yet met, the treatment period will be extended.
Possible Risks and Complications
All forms of radiation therapy for cancer treatment have side effects. This is an aggressive form of treatment for malignant tumors, and while 3D conformal technology is able to spare healthy tissues from radiation exposure, some side effects may still occur as the cancer cells are being destroyed.
However, the side effects are significantly minimized, and some are limited only to the part of the body that is being treated. These location-specific side effects may include:
For brain radiotherapy
- Hair loss
- Hearing loss
Head and neck radiotherapy
- Mouth and teeth problems
- Weight loss
- Difficulty swallowing
- Voice changes
- Hair loss
- Difficulty swallowing
- Shortness of breath
- Bladder issues
There are also general side effects, which can be short-term, such as tiredness and skin reactions, or long-term, such as fertility issues and growth hormone deficiency. There may also be some emotional effects on the patients; this is considered as a normal part of the cancer treatment process, and should also be addressed in the treatment plan, either through treatment counseling or support groups.
Zemen EM, Schreiber EC, Tepper JE. Basics of radiation therapy. In: Niederhuber JE, Armitage JO, Doroshow JH, et al., eds. Abeloff's Clinical Oncology. 5th ed. Philadelphia, PA: Elsevier Churchill Livingstone; 2013:chap 27.
National Cancer Institute. Radiation therapy and you: support for people who have cancer. Available at: http://www.cancer.gov/cancertopics/coping/radiation-therapy-and-you.