25/09/2015 14:13 BST | Updated 25/09/2016 06:12 BST

Doctor, What Is My Cancer Risk if I am on the Pill?

My 30 year old patient sat in front of me, waiting eagerly to hear what I had to say. She was worried as she had been on the pill now for a number of years and had heard conflicting information from various sources. She was a healthy young woman with no risk factors. She had tried other contraceptive methods in the past and found the Combined Oral Contraceptive Pill (COCP) or the pill as it is commonly known, suited her the most. The pill contains both estrogen (usually low dose) and progesterone.

The overall risk of cancer for a healthy woman like you is not increased on the pill, I said and there is good evidence to show there is actually a significant reduction of risk for some of the more serious gynaecological cancers such as ovarian and endometrial (womb or uterine) cancer.

Doctors have known for a while the significant benefits of taking the pill (for example, lighter flow, less painful periods and very effective contraception), including the lowered risk of certain cancers when taken for a period of time. This information is not widely known and the question of increased cancer risk is one that troubles many women taking the pill.

Taking the pill for about five years halves a woman's risk of ovarian and womb cancer while compared with non-users. We are actually seeing a slight reduction in ovarian cancer rates worldwide, probably linked to the more widespread use of the pill. The risk of colon cancer is also reduced in women taking the pill by about 20%.

There is now even further evidence confirming the reduced womb cancer risk. A recent research paper published recently in the respected medical journal (The Lancet) combining several studies showed a significant long-term protection against womb cancer with over 200,000 fewer womb cancers in the developed world over the past decade because of women being on the Pill.

'How does the pill reduce my risk of Ovarian and Endometrial (Womb) Cancer?'

The pill puts a woman's ovaries to sleep temporarily similar to pregnancy. By preventing repeated ovulation (egg release) and by modifying the shedding of the lining of the womb (menstruation or period), the hormones in the pill are thought to be the reason behind the reduction in a woman's risk of both ovarian and womb cancer. Ovarian cancer is especially hard to diagnose early, so this long term protection, even after stopping the pill is indeed good news.

'Are there some cancers I may be at increased risk of from being on the pill?'

There is some evidence to show that if women are on the Pill for more than ten years, they may be at a slightly higher risk from breast and cervical cancers, but it is possible that this is because these cancers tend to be picked up earlier as women on the pill tend to have health check-ups more often. There may be other confounding factors. For example, women on the pill tend to use barrier contraception less and so may be more exposed to HPV infection, a known risk factor for cervical cancer. However, once the pill is stopped, this small increased risk for both cancers is reversed over time.

A family history of breast cancer is also generally not a contraindication for taking the pill. If in doubt, women should consult their doctor and choose another form of contraception.

The safety profile of the pill has been carefully studied for several decades and it is important for health professionals to stress that the pill is not associated with an overall increased risk of cancer. Women can be reassured that their risk of ovarian, womb and colon cancer is significantly reduced if they have been on the pill for about five years and that this positive effect remains long after they stop the pill.

My advice to my patient was that she could take the pill safely until menopause, with regular check-ups. Long acting contraception was also discussed (for example, the implant, Mirena IUS, injections) as these come with other benefits. However, my patient for the time being, decided to stay on the pill, secure in the knowledge that the benefits of staying on the pill, including the reduced risks of ovarian and womb cancer far outweighed the risk of an unwanted pregnancy or the small potential risk of breast or cervical cancer.

Dr Nitu Bajekal, FRCOG

Consultant Obstetrician and Gynaecologist