Rectal cancers are usually treated with radiation therapy along with surgery and chemotherapy. This combination gives the highest chance of eliminating cancer cells. Radiation therapy may be given either before or after surgery. It is given together with a lower dose of chemotherapy during the weeks of radiation therapy in order to weaken cancer cells. This combination makes radiation therapy more sensitive and effective at killing the cancer. The benefits of radiation therapy for rectal cancer are:

• It makes the tumor smaller and easier to remove completely during surgery.
• In some cases it may allow surgeons to remove the tumor but preserve the anus. This means that you will continue to have control of your bowel movements through the anus. It will avoid the need for a colostomy, a bag worn on the outside of the abdomen to collect stool.
• It lowers the risk of cancer returning in the pelvic area. Radiation therapy is given over a period of weeks. A small dose is given each day to the rectum and the lymph nodes areas in the pelvis which may kill cancer cells that may have spread from the original location.

Anal Cancer

Most cancers of the anus can be cured using radiation therapy and chemotherapy alone. This cancer is not typically removed with surgery. Instead, radiation therapy and chemotherapy are given at the same time to kill cancer cells. This means that after treatment you will continue to have control of your bowel movements through the anus. Radiation therapy is given over a period of weeks. A small dose is given each day to the anus and the lymph nodes areas around the pelvis and groin, which kill cancer cells that may have escaped from the original location.

Cancer that has spread to other organs

If cancer of the rectum or anus has spread to other areas of the body, giving radiation therapy to these areas may be valuable. It can shrink or destroy these cancer areas to stop symptoms. Using radiation therapy to manage symptoms like pain, swelling, bleeding and further spreading to other parts of the body is called palliative radiation therapy. In some cases, when cancer has spread to only a few small spots, special radiation therapy techniques called stereotactic radiation therapy can completely destroy these small spots.

Cancer that has returned

In some cases, if cancer has returned in the same area that was previously treated, high advanced radiation therapy to the pelvis for a second time may be necessary. A second course may be necessary to destroy the new tumor, to shrink it so that it can be removed or to stop it from growing further.

Combined Treatment to get the best outcome

While surgery is essential for treating most cancers of the rectum, radiation therapy is typically used for anal cancer. Chemotherapy is added to radiation therapy in cancers of the rectum and anus to increase cure rate. Radiation therapy involves giving high energy X-rays to the specific area of the body that contains cancer. The dose is shaped to fit the cancerous area, damaging or killing the cancer cells. Surrounding normal, healthy tissues usually receive a lower dose than the cancer. The lower dose may cause temporary side effects and the chances of severe permanent side effects are very low. Over the past few years, radiation therapy equipment and technology has improved to allow more precise delivery of radiation therapy to the cancer. It also has allowed the normal, healthy areas of the body to receive even less radiation than it received in the past. So many of the side effects that occurred in the past are now very uncommon.

What happens when you need to have radiation therapy?

External beam radiation therapy uses invisible beams (X-rays) that are designed to pass through the body and release cancer-killing energy directly inside the cancer cells. Before you start treatment, a radiation area will be mapped to target your unique cancer while sparing normal, healthy parts of the body. This is done using a CT scan of the pelvis that you will receive at the treatment center. This session is called a simulation. You may need to wait a few to several days before starting treatment. The clinical and technical team will use the simulation scan to design your custom treatment area that covers the tumor area with cancer-killing radiation doses with much lower radiation doses to the normal, healthy parts of the body. This is called your radiation plan. It is then sent to the linear accelerator, the machine that delivers the radiation. When you start radiation therapy, the sessions are often given daily (five days a week) for a few weeks. It is necessary to give small doses per day for a period of weeks to add up to a dose to kill the cancer. Small daily radiation doses allow healthy parts of the body to recover so they do not get damaged.