3D-CRT (Three-Dimensional Conformal Radiation Therapy)

What is 3D-CRT?

Three-dimensional conformal radiation therapy (3D-CRT) is a process that radiation oncologists often use to plan external beam radiation therapy (EBRT). It involves using a machine to direct radiation beams toward cancerous tumors. The radiation beams kill cancerous cells in the tumors and shrink the tumors while reducing the chance that radiation will damage nearby healthy organs.

By using 3D-CRT, radiation oncologists get a three-dimensional view of cancerous tumors and nearby healthy organs. That perspective helps them map a tumor’s exact size and shape so that radiation conforms to or fits a tumor, a little like custom-made clothing that’s made to measure.

When do radiation oncologists use 3D-CRT?

Radiation oncologists use 3D-CRT to plan treatment for many kinds of cancer. They may use it when surgery isn’t an option.

They also may use it to plan radiation treatment done before surgery (neoadjuvant) to shrink tumors or after surgery (adjuvant therapy) to kill any remaining cancerous cells. Cancer types treated with 3D-CRT include:

• Anal cancer.
• Rectal cancer.
• Breast cancer that’s likely to recur after treatment.
• Colorectal (colon) cancer that’s spread to your lungs and liver when surgery isn’t an option.
• Certain kinds of head and neck cancer like laryngeal cancer and nasopharyngeal cancer.
• Digestive system cancers, like gall bladder cancer and intrahepatic bile duct cancer, when surgery isn’t a treatment option.
• Ewing sarcoma.
• Lung cancer.
• Prostate cancer.
• Vulvar cancer.
• Wilms tumor.

How does the radiation oncology team use 3D-CRT?

Your radiation oncology team may use 3D-CRT during treatment planning. They’ll start by using special computer software to analyze images of your body.

Typically, they’ll use images from computed tomography (CT) scans done as part of the process to diagnose your condition. They may use images from other scans done during your diagnosis, like positron emission tomography (PET) scans or magnetic resonance imaging (MRI) scans.

The computer software creates a program that maps exactly where the radiation oncology team should direct radiation beams. The program is loaded into the machine that delivers radiation.

Your radiation care team will use this map to prepare you for treatment. That happens during the simulation process. This process is when your team makes sure everything is ready for your first treatment.

Part of the simulation process uses the 3D-CRT map to pinpoint the cancer treatment field. Your team does that by placing freckle-sized markings (very small tattoos) on your skin to identify the treatment field. These markings show where you should receive radiation during each session.

Does 3D-CRT cause side effects?

No, it doesn’t, but you may have side effects from radiation therapy, and your side effects will be different depending on the area of your body receiving treatment. Even though using 3D-CRT helps protect healthy tissue, treatment can still cause damage that may lead to side effects, including:

• Fatigue.
• Nausea and vomiting.
• Loss of appetite.
• Headaches.
• Skin irritation, including soreness and redness.
• Tenderness and inflammation at the treatment site.
• Dysuria (burning sensation when you pee).
• Diarrhea.

What are the advantages and disadvantages of 3D-CRT?

The most significant advantage of using 3D-CRT is that it helps your radiation oncology team target cancerous tumors while limiting radiation damage to nearby healthy tissue.

While 3D-CRT is effective, studies suggest that intensity-modulated radiation therapy (IMRT) may kill cancerous cells and shrink tumors with fewer side effects than 3D-CRT. IMRT is another type of external beam radiation therapy. Like 3D-CRT, radiation oncology teams use scans to obtain a 3D view of cancerous tumors and nearby healthy tissue. The difference is how radiation is delivered.

In 3D-CRT, radiation is delivered in individual beams that target a tumor from different directions. In IMRT, plans call for delivering radiation in several smaller beams. Your radiation oncologist will recommend the radiation treatment plan that they believe is the best way to treat your condition.