Radiation is most often used on rectal cancer patients. Radiation therapy is not often used to treat colon cancer unless it is treating tumors that have grown next to or into other organs, to improve quality of life, or to improve surgery outcomes.

Radiation is rarely used to treat colorectal cancer by itself, but it’s a part of treatment plans calling for chemotherapy and/or surgery.

When radiation is used with surgery, it is typically used to shrink tumors so they become easier to remove before surgery. It can also be used to kill lingering cancer cells during or after surgery, something called Intraoperative Radiation Therapy (IORT).

When radiation is used alongside chemotherapy, it’s typically:

Radiation can be given simultaneously with chemotherapy. When radiation and chemotherapy are used at the same time, this is called chemoradiation or chemoradiotherapy.

Radiation therapy is typically given in the United States for rectal cancer more than 5 weeks before surgery. However, for certain patients (and in certain countries), a shorter course of 5 days of radiation therapy before surgery is appropriate and/or preferred.

Radiation is targeted toward cancer cells. Beams are aimed into the body and work by damaging cancer cells’ DNA, rendering them unable to continue dividing indefinitely. Once the damaged cancer cells die, the immune system can then break down the cells.

The two main types of radiation therapy are defined by the method that radiation is delivered – externally or internally. External-beam radiation therapy is delivered by a machine aimed at the location of your tumor. Internal radiation therapy is delivered by a radiation source that is put inside the body in solid or liquid form.

Stereotactic radiation therapy is a type of external-beam radiation therapy that may be used if a tumor has spread to the liver or lungs. This type of radiation therapy delivers a large, precise radiation dose to a small area. This technique can help save parts of the liver and lung tissue that might otherwise have to be removed during surgery. However, not all cancers that have spread to the liver or lungs can be treated in this way.

Intraoperative radiation therapy uses a single, high dose of radiation therapy given during surgery.

Brachytherapy is the use of radioactive “seeds” placed inside the body. In one type of brachytherapy with a product called SIR-Spheres, tiny amounts of a radioactive substance called yttrium-90 are injected into the liver to treat colorectal cancer that has spread to the liver when surgery is not an option. Limited information is available about how effective this approach is, but some studies suggest that it may help slow the growth of cancer cells.

A newer approach to rectal cancer is currently being used for certain people, called total neoadjuvant therapy (TNT). TNT is a novel approach for locally advanced rectal cancer (LARC), which attempts to deliver both systemic chemotherapy and neoadjuvant chemoradiotherapy prior to surgery. With TNT, both chemotherapy and chemoradiation therapy are given for about 6 months before surgery. This approach is still being studied to determine which patients will benefit most.

Your medical team overseeing your treatment plan will discuss the need for radiation with you. A radiation oncologist will be pulled in to consult on your case and create a plan.

After an initial consultation, you can choose whether to proceed with radiation.

Radiation can decrease the chance of tumor recurrence in the pelvis or near the rectum and adjacent lymph nodes by 50%, and it may also decrease the need for a permanent colostomy. There is less toxicity from chemoradiation if radiation is done prior to surgery. It’s effective, non-invasive, and generally well-tolerated for treating metastatic colorectal cancer.

Radiation can cause new mutations to be created or new antigens to be expressed. Dying tumor cells release antigens and pro-inflammatory cytokines. Radiation removes immunosuppressive immune cells.

Patients have found radiation can be inconvenient, as it’s needed daily in many cases. It can also cause poor wound healing if surgery is performed after radiation therapy. Radiation’s side effects build over time, and the damage may appear years after the treatments. It has also left patients with incontinence, urgency, burning, and other side effects related to the tissue damage.

Radiation appointments are outpatient, and they are much quicker compared to days in the infusion clinic. However, they are daily appointments that usually last between 30-60 minutes.

You’ll want to wear loose clothes to your radiation appointment because you’ll need the radiation field uncovered. A nurse will guide you into a cold, dark room where the radiation machine sits. The mold that was cast during your introductory appointment will be used as the techs work to position you on the table. The techs will also use the dots to line up the radiation beams. The majority of your appointment will be spent getting you lined up with the machine.

Once you’ve been placed, everyone will clear out of the room before the radiation machine begins. Because the nurses and techs are exposed to the radiation all day, every day (as opposed to your 30 min. each day), they will be wearing protective gear and stand behind glass as you receive your treatment.

Radiation itself does not hurt, and once you leave, you’re safe to be around other people and pets.

Radiation only affects the area of the body where it is administered (except in the case of systemic radiation therapy). Thus, radiation therapy for colorectal cancer should not cause hair loss, unless radiation is administered to the scalp.

However, when given locally, radiation can also damage or kill nearby healthy cells that can cause negative side effects. Many side effects disappear after treatment, however some may linger or appear within weeks, months or years.

Your ability to carry on normal activities depends on the type of radiation therapy being administered and its frequency. Depending on your radiation therapy schedule, you may need to stay at the hospital. Some patients may be able to perform normal daily activities, like working full-time or part-time, without much interruption, while others may be too fatigued. Many side effects from radiation therapy typically go away after treatment in a few weeks or a few months, but some can linger for years.

Over your lifetime, there is a limit to the amount of radiation you can be exposed to. If you have had radiation therapy in the past, you may not be eligible to receive radiation to the same area of your body if you’ve reached your safe lifetime dose of radiation.

However, if you have already reached your lifetime limit in one area of your body, you may be eligible to receive radiation therapy again targeted toward another area.