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NCCN Guidelines for Patients



Rectal Cancer, Version 1.2017


Overview of cancer treatments

Radiation therapy

External radiation

For rectal cancer, the most common radiation

method is EBRT (









A large machine makes high energy x-rays used for

treatment. This machine is called a LINAC (





See Figure 11


The beams of high-energy x-rays are a type of

photon radiation. They will move through your body

at the speed of light. There is no ongoing radiation

inside of you after the treatment session. You will not

have to avoid people.

It takes a team of people to perform the radiation

therapy. The radiation team consists of doctors,

medical physicists, dosimetrists, nurses, and

radiation therapists. Your team will work together to

design your treatment plan and provide treatment.

Planning session

A planning session is needed to map out your

treatment. The planning process is called simulation.

It involves obtaining a CT scan of your body in the

position that is needed for treatment. The scan is

only used for treatment planning.

You will not have to do much to prepare. Don’t eat

a heavy meal for 4 hours beforehand. Think about

wearing easy-to-remove clothes since you’ll undress

from the waist down. You’ll wear a gown during the

session. The planning session takes about one hour.

In the CT room, a mold may be created and fitted

to your body. The mold will help you stay in place

during treatment. Often, people lie face down on the

mold that is on top of the CT table. Your arms may be

raised above your head. Colored laser lights will be

used to help position you.

You may be given a contrast dye. It will make your

rectum and lymph nodes easier to see on the

scans. Contrast may be given with a rubber catheter

inserted into your rectum. Air may also be pumped

in or removed. Next, a CT scan will be done. The

medical physicist or dosimetrist may take more

measurements for treatment planning.

The CT images will be transferred to a treatment

planning computer. Your rectum and other organs will

be seen on the scan. This information will show your

radiation oncologist where to direct the radiation.

After the treatment sites are set, your skin will be

marked for treatment sessions. Your skin will be

marked with a felt pen. Sometimes, set-up marks are

made with tiny permanent tattoos. Photos of your set

up are taken. The marks and photos will be used to

position you for daily treatment sessions.

Figure 11

External beam radiation therapy

Radiation therapy is often delivered from a

large machine called a linear accelerator. The

rays pass through skin and travel to the tumor.

Healthy tissue is protected using modern types

of treatment.