Hormones and cancer in the UK - statistics

The lifestyle choices that determine hormone levels are not as straightforward as stopping smoking or eating healthily and are largely dictated by reproductive or genetic factors, over which individuals may have little or no control.

Table 5.1 shows a summary of what we know about hormones and cancer risk.

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section reviewed 01/06/05
section updated 01/07/09

The most recent worldwide reanalysis of 18 prospective studies showed no association between levels of endogenous sex hormones and risk of prostate cancer overall.2

Risk of ovarian, endometrial and breast cancers increases with earlier age at menarche and later menopause, and reduces with each full-term pregnancy (the first full-term pregnancy providing more protection than successive ones).3,4 There is a transient increase in risk of breast cancer with each full-term pregnancy after the age of 25, and this is most marked with a woman’s first pregnancy. Uniparous women with a first full-term pregnancy after the age of 30 have a higher breast cancer risk than childless women until their late 50s.5

The total fertility rate (average number of children per woman) in women in England and Wales in 20011 was 1.9, which is slightly higher than the mid-1970s, but lower than the mid-1960s, when it was almost 3.16

Breast cancer risk is reduced by around 4% for each year a woman breastfeeds.4 Evidence for a protective effect against ovarian cancer is mixed.6,17,18 The European Prospective Investigation into Cancer showed no effect of breastfeeding on endometrial cancer risk.7 According to the latest survey, around 76% of mothers in the UK breastfeed initially, compared with 62% in the 1990s, but only 34% of women breastfeed for more than four months and only a quarter for more than six months.8

A study published in December 2011 estimated that around 3% of breast cancers and almost 18% of ovarian cancers (equivalent to around 1.7% of all cancers in women in the UK) are linked to women breastfeeding their children for less than six months.22

section reviewed 01/06/05
section updated 01/01/12

A meta-analysis of European case-control studies indicates that use of OCs for five or more years results in a 50% reduction in risk of ovarian cancer which remains for more than 20 years.9 Case-control studies have consistently reported a 40 to 60% reduction in risk of endometrial cancer, increasing with duration of use, among users of combination OCs.10 There is a slight transient increase in risk of breast cancer while OCs are taken.11,12

Use of OCs for more than five years results in a duration-dependent increased risk for cervical cancer after adjustment for potential confounders including human papillomavirus (HPV) status (see infections section below), smoking and use of barrier contraceptives. Risk falls once use of OCs is stopped.13

A study published in December 2011 estimated that there were around 1,600 fewer cases of cancer in the UK in 2010 than there would have been without use of OCs, due to their protective effect against ovarian and womb cancer, which outweighed the increased risk of breast and cervical cancers.23

section reviewed 01/06/05
section updated 01/01/12

Women taking oestrogen-only hormone replacement therapy (HRT) are at an increased risk of endometrial and ovarian cancers.14 The risk of uterine cancer is approximately doubled after five years, while the risk of ovarian cancer increases by about 25% for the same duration of use.3,10 Combined oestrogen-progestagen HRT increases risk of ovarian cancer by a smaller amount.19 Risk of uterine cancer is slightly increased in women using cyclic-combined HRT, but slightly reduced in those using continuous-combined HRT.20

The UK ‘Million Women Study’ reported breast cancer RRs for current use of oestrogen-progestagen therapy or oestrogen only of 2 and 1.3, respectively. Risk increased with duration of use, with risk ratios of 2.3 for 10 or more years of combined HRT, compared with 1.5 for less than one year. There was a marginally increased risk in women who stopped HRT less than a year before entering the study, but no difference in risk between never users and women as a group who stopped therapy at some point in the previous five years.15

In the UK, use of HRT peaked in 2000-01, when approximately 25% of women aged 45-69 were using it. The percentage had fallen to half that by 2006. It has been estimated that, in 2005, there were 1,400 fewer cases of breast cancer in women aged 50-59 in the UK than there would have been if use had not fallen.21 Nonetheless, a study published in December 2011 estimated that around 1,500 cases of breast cancer in the UK in 2010 were linked to use of HRT, in addition to around 100 womb cancers and 50 ovarian cancers (equivalent to around 1% of all cancers in women in the UK).23

section reviewed 01/06/05
section updated 01/01/12