Sexual contact increasing the risk of developing cancer

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It has been known for some time that women who start having a sex at a young age, have multiple partners or have sex with men who have had multiple partners are more likely to get cancer of the cervix. This was found to be caused by exposure to a virus called the Human Papilloma Virus (HPV). This can cause common warts but at a more sinister level can damage the cells at the entrance of the uterus - the cervix. Initially exposure to the virus causes some inflammation and minor changes in the cells causing dysplasia. Later, some cancer cells are formed but they do not show signs of invasion - this is the precursor to cancer known as CIN (cervical intraepithelial neoplasm). There are three levels of severity depending on the volume of the cervix involved (CIN I-III). This can be picked up with a cervical smear and can be treated locally with wedge resection of the affected area. This usually successfully prevents the formation of full blown cervical cancer so it is important that women who had started to have sex attend regularly for their smear tests. This virus can also cause other types of cancer including vulva and penis.

The other virus which can be caught through sexual contact is the Acquired immunodeficiency virus (AIDS).  This virus causes cancer by reducing the immune defence against cancer. Although, cancer cells have grown originally from our own body there are some differences in their genetic makeup and the proteins they express on their cell surfaces. Only those cells which are able to escape the body’s immune surveillance can progress into a full blown cancer. Everyday we have thousands of cancers developing which are killed off by our immune system. AIDS related cancers include Kaposi's sarcoma (a purple skin cancer), lymphoma particularly of the head.

How to avoid catching viruses during sexual contact. Avoid multiple partners, use a condom. Men should check their penile regularly for signs of warts and women should attend cervical screening regularly. A vaccine is now available for HPV, if a women is planning to have multiple partners or have unprotected sex with a man who may have had warts or multiple partners this vaccine would significantly reduce the risk of cervical cancer. If a man has had unprotected anal sex or been an intravenous drug abuser ask him to have a HIV test and use a condom.

Risks of sex after cancer

Some cancer treatments may make sex difficult e.g. vaginal pain and dryness or erectile dysfunction.

In terms of safety, the most important is the risk of pregnancy during chemotherapy or radiotherapy. You should not become pregnant during these treatments as they will damage a growing baby. You should still take contraceptive precautions even if your periods have stopped, as you could still become pregnant. The contraceptive pill my increase the risk of blood clots during chemotherapy and certainly with breast cancer they should be stopped, so it is best to use a condom instead.

There are no known risks of catching cancer off a partner. The only possible association would be HPV infection and cervical cancer but otherwise it is quite safe to have sexual intercourse during chemotherapy. During radiotherapy the vagina may get sore and require the use of dilators