Radiation therapy

When radiation therapy is used

Radiation therapy may be recommended for rectal cancer but is rarely used to treat colon cancer. 

You may have radiation therapy:

Before surgery (neoadjuvant) – Radiation therapy is used before surgery to shrink the tumour. This makes it easier for the surgeon to remove the cancer and reduces the risk of the cancer coming back.

After surgery (adjuvant) – If rectal cancer is more advanced than expected, radiation therapy may be used after surgery to kill remaining cancer. This is only if radiation therapy wasn’t given before surgery.

Radiation therapy may be given on its own or with chemotherapy (chemoradiation), which makes cancer cells more sensitive to radiation.

Having radiation therapy

External beam radiation therapy (EBRT) is the most common radiation therapy for rectal cancer. A machine called a linear accelerator delivers a high dose to the affected area, with lower doses to surrounding tissue, reducing side effects.

You will meet with your radiation oncologist for them to explain details about treatment, the number of sessions you need to have and whether you will have chemotherapy with your radiation treatment. For your radiation oncologist to design your treatment, a planning CT scan will be done in the treatment position. Small marks, like a freckle, may be made on your skin to help set you up in the exact same position for each treatment. It may take a few weeks to plan the treatment.

Treatment is given daily, on weekdays. During treatment, you lie on the table of the radiation therapy machine. Each time you have treatment, you lie in the same position as you were in when you had the planning CT scan.

Each treatment only takes a few minutes, but you may be on the treatment table for 10–20 minutes because of the time it takes to set you up accurately. The treatment is painless and can’t be seen or felt.

After finishing neoadjuvant treatment, there will be a break before surgery. This gives time for the radiation therapy to have its full effect.

Side effects of radiation therapy

Most side effects are temporary and go away weeks or months after treatment. Feeling tired is common. Radiation therapy for rectal cancer is usually given over the pelvic area, which can affect your sexual function and ability to have children (see fertility).

Radiation therapy can irritate the bowel and bladder. This may mean:

• needing to pass urine (wee or pee) more often or burning when you do (cystitis)
• redness and soreness in the treatment area
• needing to poo urgently/suddenly or incontinence
• diarrhoea
• constipation
• mucus or small amounts of blood coming out of the anus. 

Radiation therapy can cause the skin or internal tissue to become less stretchy and harden (fibrosis). It can also inflame the lining of the rectum (radiation proctitis).

People react to radiation therapy differently, so some people may have few side effects, while others have more. Your treatment team will talk to you about possible side effects and how to manage them.

Sexual function and fertility after radiation therapy

You may find it helpful to share your feelings about any sexual or fertility issues with your partner, a counsellor, a sexual therapist or a fertility specialist.

For males

• Radiation therapy can damage sperm or reduce sperm production. This may be temporary or permanent.
• Most doctors suggest using contraception and not having unprotected sex during and for one month after radiation therapy treatment.
• Radiation therapy can damage the blood vessels and nerves that produce erections. This sometimes leads to problems getting and keeping erections. Your doctor may prescribe medicine or refer you to a specialist clinic to manage erection issues.
• You will be able to store sperm at a hospital or fertility clinic before treatment starts. Talk to your doctor about this.

For females

• Radiation therapy can cause the vagina to become shorter and narrower, making intercourse painful.
• Your doctor may suggest using a vaginal dilator after treatment ends and the area has healed. A vaginal dilator can help gradually widen the entrance and prevent the side walls sticking together. Your doctor or a physiotherapist can provide practical advice on how to use a dilator.
• Talk to your doctor about creams and moisturisers to help with vaginal discomfort and dryness.
• Extra lubrication may make sexual intercourse more comfortable. Choose a water-based or silicone-based lubricant without perfumes or colouring.
• In some cases, radiation therapy can stop the ovaries producing oestrogen and progesterone. This can cause menopause – after menopause you will not be able to conceive a child.
• Menopause hormone therapy (MHT) may help with menopause symptoms.