Transcript Epidemiology and risk factors for breast cancer

Epidemiology and risk factors for
breast cancer
Dr.Mina Tajvidi
oncologist
Epidemiology and risk factors for
breast cancer
In the US, breast cancer is the most
common female cancer, the second
most common cause of cancer death
in women, and the main cause of
death in women ages 40 to 59. About
one-half of cases can be explained by
known risk factors
Epidemiology and risk factors for
breast cancer
Incidence — Approximately 210,000 new cases
of invasive breast cancer are expected to be
diagnosed in the United States in 2010, and
40,000 die from the disease [1]. The lifetime
probability of developing breast cancer is one in
six overall (one in eight for invasive disease)
Global variation — Globally, breast cancer
incidence rates are highest in North America and
northern Europe, and lowest in Asia and Africa
Age and gender
Age and gender are among the strongest
risk factors for breast cancer
 Breast cancer occurs 100 times more
frequently in women than in men
Incidence rates rise sharply with age
until about the age of 45 to 50 when the
rise is less steep
RACE/ETHNICITY
BENIGN BREAST DISEASE
Single nonproliferative lesions (fibrocystic
change, solitary papilloma, simple
fibroadenoma) are not associated with an
increased risk for breast cancer. The
presence of multiple nonproliferative
lesions may increase the risk for breast
cancer modestly
The more important precursors of
noninvasive or invasive breast cancer are
proliferative lesions, particularly those
with cytologic atypia.

PERSONAL HISTORY OF BREAST
CANCER
A personal history of invasive or in situ
breast cancer increases the risk of
developing an invasive breast cancer in
the contralateral breast
Socioeconomic status
Weight
Weight and body mass index (BMI) have opposite
influences on postmenopausal as compared to
premenopausal breast cancer.
Higher weight/BMI and postmenopausal weight gain have
been associated with a higher risk of breast cancer in
multiple studies [34-39]. The influence of weight is
strongest in women who do not use HT
 mean serum estradiol levels were significantly higher
among women with a BMI ≥29 kg/m2 compared to those
with a BMI <21 kg/m2 (10 versus 4.7 pg/mL)
 premenopausal women with a BMI ≥31 kg/m2 were 46
percent less likely to develop breast cancer than those with
a BMI <21 kg/m2
Height
In the majority of studies, increased
height has been associated with a
higher risk of both premenopausal
and postmenopausal breast cancer
 women who were at least 175 cm
(69 inches) tall were 20 percent more
likely to develop breast cancer than
those less than 160 cm (63 inches)
tall

Physical activity
Regular physical exercise appears
to provide modest protection against
breast cancer
Alcohol
breast cancer risk is higher for
women consuming moderate to high
levels of alcohol
Fat intake
Animal and ecologic studies have
shown a positive correlation between
fat consumption and increased breast
cancer risk
Red meat
Calcium/vitamin D
 inverse association between breast cancer risk
and the intake of low-fat dairy products, calcium
(mainly dairy intake), and vitamin D (mainly nondairy intake) in premenopausal but not
postmenopausal women
Antioxidants
 There is no strong evidence for an effect
of intake of vitamin E, or C or betacarotene on breast cancer risk [94,95]. The
data are conflicting on vitamin A and breast
cancer.
Smoking
many showing modestly increased
risk
REPRODUCTIVE/HORMONAL 
RISK FACTORS
 Prolonged exposure to and higher
concentrations of endogenous estrogen
increases the risk of breast cancer.
Age at menarche and
menopause
 Younger age at menarche is associated
with a higher risk of breast cancer
Later menopause increases breast cancer
risk
Menstrual patterns/infertility
These events affect the number of
lifetime ovulatory cycles and influence a
woman's cumulative exposure to ovarian
hormones.
several epidemiologic studies suggest a
link between infertility due to anovulatory
disorders and a decreased risk of breast
cancer
Parity
Nulliparous women are at
increased risk for breast cancer
compared with parous women
The protective effect of
pregnancy is not seen until after
10 years following delivery

Age at first birth
 the cumulative incidence of breast
cancer up to age 70 for parous versus
nulliparous women was 20 percent
lower if the first birth was at age 20,
10 percent lower for first birth at age
25, and 5 percent higher if the first
birth was at age 35
Abortion
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Breastfeeding
A protective effect of breastfeeding has
been shown in multiple case-control and
cohort studies
 The protective effect of breastfeeding
may be stronger for the development of
breast cancer during the premenopausal
years and in women with a first-degree
relative with breast cancer
Bone density
 women with higher bone density
had a higher breast cancer risk
Because bone contains estrogen
receptors and is highly sensitive to
circulating estrogen levels
diabetes
Although some studies suggest a
slightly increased risk of breast
cancer in postmenopausal women
with type 2 diabetes [152-156],
others do not [157-160]. Diabetes is
not generally considered a significant
breast cancer risk factor
Breast density
Besides increasing the difficulty of mammographic
detection, the presence of dense breast tissue is also
independently associated with an increased risk of breast
cancer
In multiple independent epidemiologic studies, the risk of
breast cancer is four to five times greater in women with
mammographically dense breasts (usually defined as ≥75
percent density) compared to women of similar age with
less or no dense tissue
Breast density and bone mineral density are both markers
for cumulative exposure to estrogen.
Oral contraceptives
Many epidemiologic studies have failed
to demonstrate an association between
oral contraceptive use and the risk of
breast cancer.
Hormone therapy
The use of combined estrogen plus
progesterone is associated with an
increased relative risk of breast
cancer;
Long-term use of HT is associated
with the highest risk. In contrast,
short-term HT appears not to
increase the risk of breast cancer
significantly, although it may make
mammographic detection more
difficult

.
Infertility treatment
There does not appear to be an
increased risk of breast cancer in
women treated with fertility drugs.
 Further investigation is required.
FAMILY HISTORY AND GENETIC
RISK FACTORS
Family history is an important risk factor
for breast cancer. However, a positive
family history is only reported by 15 to 20
percent of women with breast cancer.
the risk of breast cancer before age 40
was increased 5.7-fold if one relative had
breast cancer before age 40.
5 to 6 percent of all breast cancers are
directly attributable to inheritance of a
breast cancer susceptibility gene such as
BRCA1, BRCA2, p53, ATM, and PTEN

EXPOSURE TO IONIZING
RADIATION
Exposure to ionizing radiation of the chest at a young age,
as occurs with treatment of Hodgkin lymphoma or in
survivors of atomic bomb or nuclear plant accidents, is
associated with an increased risk of breast cance
The most vulnerable ages appear to be between 10 to 14
(the prepubertal years), but excess risk is seen in women
exposed as late as 45 years of age [191]. After age 45, there
does not appear to be any increased risk
mammography, chest radiographs, diagnostic spine
imaging [192,193], CT scans), is controversial. At least for
women without an inherited predisposition to breast
cancer, the impact of radiation-associated breast cancer
from routine diagnostic imaging is thought to be small to
nonexistent

ENVIRONMENTAL EXPOSURES
Organochlorines include polychlorinated
biphenyls (PCB's), dioxins, and organochlorine
pesticides such as DDT. These compounds are
weak estrogens, highly lipophilic, and capable of
persisting in body tissues for years. However,
most large studies have failed to find an
association
Cosmetic breast implants, electromagnetic
fields, electric blankets, and hair dyes have not
been associated with increased risk in most
studies
Nocturnal light exposure/Night
shift work
 At least three studies and a
meta-analysis support an
association between exposure to
light at night and the risk of
breast cancer
NSAID use
Aspirin and other nonsteroidal
antiinflammatory drugs (NSAIDs) can
inhibit the formation of both benign
and malignant tumors in the colon.
 the data regarding a possible
protective effect of NSAID ingestion
on breast cancer risk are mixed. Only
one randomized trial has evaluated
the impact of low-dose aspirin on
cancer prevention

Antibiotic use
 increasing cumulative days of
antibiotic use for any condition was
associated with a significantly greater
risk of breast cancer.
 they underscore the importance of
carefully considering the use of
antibiotics in the absence of a clear
indication.
Screening for breast cancer
A variety of imaging modalities
have been developed for
identifying lesions that are
suspicious for breast cancer.
Mammography remains the
mainstay of screening for breast
cancer

Mammography
digital mammography was more accurate for
premenopausal and perimenopausal women, and
for women with dense breasts
film mammography remains an acceptable
screening modality for all women. Digital
mammography, when available, may offer a small
screening advantage in women younger than 50
years old.
Magnetic resonance imaging
The combination of MRI and mammography is
recommended by the American Cancer Society in
women at very high risk of breast cancer
Nearly all invasive breast carcinomas enhance
on gadolinium contrast-enhanced MRI
The reported sensitivity of breast MRI is 88 to
100 percent for invasive carcinomas; it is lower for
DCIS in most, but not all
Age to initiate screening
The American Academy of
Family Physicians recommends
screening mammography every
one to two years for women ages
40 and older
Age to discontinue :age 74.
