Radiotherapy treats cancer by using high-energy rays (radiation) which destroy the cancer cells, while doing as little harm as possible to normal cells. Radiotherapy commonly causes fatigue (tiredness that doesn't go away with rest) which may last for several weeks or months. In this situation, sex may be one of the last things on your mind, or you just may be too tired to actually have sex.

Pregnancy and radiotherapy

Radiotherapy can cause damage to an unborn child. So, if you have not yet had your menopause, you may be asked by the staff in the radiotherapy department to have a pregnancy test before you start your radiotherapy. You will need to use effective contraception throughout your radiotherapy treatment. You can discuss this with your doctor or specialist nurse.

If you are pregnant before your cancer is diagnosed and your radiotherapy starts, it is very important to discuss with your doctor the pros and cons of continuing with your pregnancy. It is sometimes possible to delay starting radiotherapy until after the baby is born. It depends on the type of cancer you have, the extent of the disease, and how advanced the pregnancy is. You will need to talk to your doctor about your pregnancy. It is important to be fully aware of all the risks and alternatives before making any decisions. You can also talk to the nurses at Cancerbackup.

Pelvic radiotherapy

Any radiation to the pelvic area for cancer involving the rectum, bladder or cervix, affects the ovaries and reduces the production of female hormones. Sometimes this is temporary, but usually the ovaries permanently stop producing hormones. The production of hormones gradually decreases over about three months. This will cause symptoms of the menopause, such as hot flushes and mood swings. In the long-term, the low hormone levels can increase the risk of weakened bones (osteoporosis) and heart disease.

Your doctor may be able to give you hormone replacement therapy (HRT), which can make up for these changes. If you have had breast cancer or a hormone-sensitive gynaecological cancer, you may be advised not to take HRT. It is helpful to discuss this with your doctor.

A woman who has already had her menopause will have far fewer hormonal changes than a woman whose ovaries were still working before the radiotherapy treatment.

The vagina can be affected by radiotherapy to the pelvic area. It becomes sore and tender in the early stages and for a few weeks afterwards. Over time, this irritation may leave scarring. This makes the vagina narrower and less flexible.

We have further information about coping with the effects of pelvic radiotherapy in women.

Radiotherapy may affect sexual function when it is given to the pelvic area for cancers of the prostate, rectum and bladder.

Some men feel a sharp pain as they ejaculate if they have recently had radiotherapy treatment. This is caused by radiation irritating the urethra. The pain usually disappears within a few weeks after the treatment has ended.

Impotence

Radiotherapy to the pelvic area can reduce a man’s ability to have an erection. Up to 30% of men (3 in 10) will have problems getting or keeping an erection after radiotherapy for prostate cancer. In affected men, the erections are less strong than before the treatment and this gradually gets worse over a year or two. This occurs because of nerve damage or because blood vessels that supply the penis become scarred and are unable to let enough blood through to fill the penis. Some men get an erection but then lose it. Other men are unable to have an erection at all. Treatment with drugs can help some men to get and maintain an erection after radiotherapy.

Overcoming impotence

Treatments that can help to overcome impotence are discussed in our information on solutions to sexual problems. It is thought that using these treatments soon after the radiotherapy may help to prevent impotence in some men.

Dry ejaculations

In men who can still have and maintain erections, it is very common to have dry ejaculations. When this happens, little or no semen is ejaculated at orgasm. This is not harmful but can worry you if you don't expect it.

We have further information about coping with the effects of pelvic radiotherapy in men.

For both men and women, radiotherapy to the pelvic area will cause infertility (the inability to have children). Radiotherapy to other parts of the body may also give a dose to the sexual organs that will cause infertility. In women the ovaries may stop making eggs, and in men the production of sperm may stop. If they happen, these changes cannot be reversed and infertility will be permanent. If you wanted to have children, this can be very difficult to cope with.

Our section on possible ways of preserving fertility discusses the options for dealing with infertility, as does our section on fertility and cancer.

See feelings about infertility for the feelings and emotions you may have about fertility.

It is important that you discuss the risk of infertility fully with your doctor before you start treatment. If you have a partner they will probably want to join you at this discussion. Then you can both be aware of all the facts and have a chance to talk over your feelings and the options for the future.