OzEMedicine - Wiki for Australian Emergency Medicine Doctors

see also:

• neoplasia / cancer / tumours
• US National Cancer Institute - breast cancer prevention, aetiology and genetics

• breast cancer risk calculator
• PH carcinoma-in-situ or carcinoma of breast:
  • ductal carcinoma in situ (DCIS) and lobular carcinoma in situ (LCIS) are at increased risk
  • if a woman has had breast cancer, her risk of developing a second primary breast cancer is 2-6 times the risk seen in the general population of developing a primary breast cancer
• PH breast irradiation:
  • radiotherapy for Hodgkin's lymphoma - doubles lifetime risk
  • CT scanning during pregnancy
  • the effect of radiation on the breast is strongly related to age at exposure ie the younger the woman is exposed the greater the excess risk.
• hair dye
• genetic mutations:
  • BRCA1 - also assoc. with ovarian, bowel and prostate cancers
  • BRCA2 - also assoc. with ovarian, pancreatic and prostate cancers
  • other rare familial disorders such as Li Fraumeni synd, Cowden's synd, Peutz-Jegher's synd., ataxia telangiectasia.
  • appears to be a correlation with severe acne which appears to have shared genetic causes
  • since breast cancer affects one woman in nine there will be many women who have a mother or sister with the disease. But only if there are several family members with early onset breast cancer is there a likelihood of a significant inherited predisposition to the disease
• breast density:
  • higher density (less fat) is a risk factor, and appears mainly to be genetic, although menopausal status, parity and weight are factors.
  • women with denser breasts have 2-6 times the risk of breast cancer compared to women with less dense breasts
• benign breast disease:
  • women who have had biopsies that showed proliferative breast disease without atypia have a 2-fold increased risk, while women with atypical hyperplasia have a 2-5 fold increased risk
• alcohol intake:
  • increase of risk of 7% for each additional 10 grams of alcohol consumed on a daily basis
  • risk seems particularly an issue prior to 1st pregnancy as alcohol consumption is thought to reduce metabolism of oestrogen thereby causing high levels of oestrogen
• no direct association between tobacco and breast cancer.
• age:
  • the majority of breast cancer cases occur in women older than age 50.
  • risk of breast cancer in UK women:
    • aged < 25 years = 1 in 15,000
    • aged < 30 years = 1 in 1,900
    • aged < 40 years = 1 in 200
    • aged < 50 years = 1 in 50
    • aged < 60 years = 1 in 23
    • aged < 70 years = 1 in 15
    • aged < 80 years = 1 in 11
    • aged < 100 years = 1 in 9
  • additional risk factors for post-menopausal women:
    • body mass index if not on HRT
      • after the menopause, when the ovaries stop producing oestrogen, adipose tissue is the primary source of endogenous oestrogen so obese and overweight women are exposed to higher levels of oestrogen.
      • obesity is also associated with lower levels of sex hormone binding globulin (SHBG) which increases the amount of bioavailable oestradiol
      • 30% increased risk if BMI > 28, and 2x death rate if BMI > 40
      • 20% increased risk if BMI 25-30 when compared with women with BMI 20-25 at age 50-59 yearsuk_million_women_study_2010
    • age at natural menopause
      • for each year menopause is delayed, there is an approximate 3% increase in breast cancer risk
    • use of hormone replacement therapy
      • the risk increase of breast cancer for current users of HRT is 66%
      • the effect is substantially greater for oestrogen-progestagen combinations than for oestrogen only HRT. Risk increases with duration of use: the risk for current users of oestrogen-progestagen combinations for 10 or more years was 2.3 compared to 1.7 for 1-4 years of use.¹⁾
      • risk decreases with cessation of use; past users have a similar risk to never users
    • prior false-positive mammogram
• race:
  • Caucasians have higher risk of developing it than those of African descent or those from rural China or Japan.
• height:
  • taller women are at slightly higher risk
  • relative risk for UK women 1.75 metres or taller compared with women shorter than 1.6 metres was 1.22 for all women and 1.28 for postmenopausal women
  • increase in relative risk of 7% for each additional 5 centimetres in height for postmenopausal women and 2% for premenopausal women.²⁾
• age at menarche:
  • women who had their first menstrual period before age 12 have a slightly increased risk of breast cancer
  • relative risk for premenopausal breast cancer is reduced by an estimated 7% for each year that menarche is delayed after age 12 years, and by 3% for postmenopausal breast cancer
• age at first live birth, breast feeding and FH breast cancer:
  • the relative risk of developing breast cancer increases by 3% for each year of delay of first live birth.
  • a woman has a 7% decreased risk of breast cancer per live birth after the 1st birth and her risk drops by a further 4% for every year of breastfeeding ³⁾
  • it is estimated that 5% of breast cancers could be prevented every year if women were to breastfeed their children for an extra six months.
  • see table below of relative risks⁴⁾

• prophylactic anti-oestrogens:
  • tamoxifen and the osteoporosis agent, raloxifene have both been shown to substantially decrease the incidence of breast cancer by ~50% when used in post-menopausal women aged over 35 years ⁵⁾.
  • it would seem women with a life time risk of breast cancer of 20% or more should be offered raloxifene as it has less adverse effects than tamoxifen while having the same 50% reduction in invasive breast cancer incidence.
• screening mammograms:
  • women aged 40yrs and older should be offered screening mammogram every 1-2 years.
  • those younger than 50yrs may benefot more from digital rather than film mammography.
• HPV vaccination:
  • (human papilloma virus (HPV)) type 18 has been detected in ~50% of breast cancers⁶⁾, and although the evidence is not conclusive, if breast cancer is a sexually transmitted disease via hpv then HPV vaccination may decrease the incidence of breast cancer. It is thought that hpv is spread by touch from the genitals to the nipples.