Radiotherapy before surgery for rectal cancer

Does it work?

If you have rectal cancer, then radiotherapy before surgery may lower the likelihood that your cancer will come back and may help you live longer. But we can't be sure as some research shows that it doesn't help many people more than surgery alone does.[1] [2]

Rectal cancer means the cancer is in a part of your bowel called your rectum. To read more, see More about your colon and rectum.

You're likely to feel ill from this treatment, and you may not be able to do things that you would normally do. Having radiation therapy for a short time (a short course) has few side effects, but having it for a longer time (a longer course) can have more serious side effects.

What is it?

Radiotherapy is the use of radiation, usually X-rays, to treat cancer. It treats only the area of tissue that it touches.

You can have radiotherapy before or after surgery. If you have it before, it is used to shrink the cancer. This may make it easier to remove the whole tumour during surgery and it may make it less likely that your cancer will come back after your operation. If you have radiotherapy after surgery, it is used to kill any cancer cells left behind or to shrink any tumour that might be left. The information here is about radiotherapy before surgery.

Radiotherapy is not usually used to treat tumours in the colon, but it is used to treat tumours in the rectum that are stage 2 or 3 (Dukes's stage B or C). These tumours have spread through the wall of the rectum, although the cancer cells may not have reached the lymph nodes.

With these types of tumours, there is a high risk that the cancer will come back after surgery or spread to organs nearby.[3] [4] [5] [6] This risk can be as high as 70 percent in some people.[3] And if cancer spreads to organs nearby (such as the bladder, the prostate or the vagina), it can be very painful. Radiotherapy (both before and after surgery) is one treatment doctors use to improve the outlook for people with these types of tumours.

Radiotherapy has been used to treat cancer for more than 100 years. Most radiotherapy uses high-energy X-rays that are produced by a machine called a linear accelerator. This machine gives the X-rays extra energy. The X-rays have about 500 to 1,000 times more energy than the ordinary X-rays used to get a picture of your body. This added energy means that the X-rays can go deeper into tissues and destroy cancer cells. But you won't feel these X-rays when you have radiotherapy. The treatment takes a few minutes and you need to keep still.

The problem is that radiotherapy kills some normal cells as well as cancer cells. But it kills only cells that are dividing and growing. By treating people with several bursts of radiotherapy, there's more chance of killing more cancer cells than normal cells. This is because cancer cells divide and grow faster than normal cells, so they are more likely to be killed by repeated doses of radiation.

How long you have radiotherapy can vary. You may be given it five days a week for five to seven weeks before surgery for rectal cancer. But some hospitals give only five days of radiotherapy before surgery. The results of this shorter treatment are still being investigated.

You won't feel anything during your treatment, but you may be uncomfortable because you have to stay in one position.

If you want to know more about how radiotherapy interrupts the life cycle of cells, see How does radiotherapy work?

How can it help?

Radiotherapy before your operation may lower the likelihood that your cancer will come back and help you to live longer than if you had just surgery alone. But we don't know this for sure. The research shows different things and it doesn't provide clear answers as to whether the risks of radiotherapy outweigh the benefits.

Some research shows that if you have rectal cancer and you have radiotherapy before surgery:

• Your chance of being alive after five years increases by 16 percent[1]
• The chance that your cancer will come back in the same place during the next five years to 10 years is halved.[1] [2] [7] In studies, about 10 percent of people who had radiotherapy before surgery had cancer in their colon or rectum again within five years, compared with 25 percent of those who had surgery only[2] [7]
• You may be less likely to get cancer again than if you were to wait to have radiotherapy until after your operation.[8]

However, these figures vary depending on the stage of your rectal cancer. Your doctor may suggest that you have radiotherapy before surgery if you have a large tumour. You don't usually need radiotherapy before surgery to remove a small tumour.

Also, some studies have found no difference between having surgery alone and having radiotherapy before surgery in the likelihood that your cancer will come back or in the likelihood that you will live longer than five years.[2] [7] [9]

But all the studies found side effects from radiotherapy, such as wound infections, diarrhoea, bowel blockages and pain after surgery (see below).

Why should it work?

When you have radiotherapy before surgery, the goal is to shrink the size of the tumour so that it's easier for the surgeon to remove all of the growth. If a tumour is too big to operate on, radiotherapy is also used to kill some of the cells so the tumour becomes small enough for surgery. Doctors use radiotherapy to try to kill cancer cells while avoiding normal tissue.[10]

Can it be harmful?

Yes, having a long course of radiotherapy before surgery for rectal cancer can make you feel unwell and disrupt your life.[9] [11] But compared with older techniques, modern therapy causes less damage to the healthy tissue around the cancer. Risks are continually being reduced as better ways of giving radiotherapy are developed.

The side effects of radiotherapy can be divided into two types: those that happen soon after treatment (acute side effects) and those that happen a while after treatment (long-term side effects).