Invasive breast carcinoma - IARC

f i r s t - d e g ree re l atives of breast cancer
probands diagnosed before age 80 estimated
a relative risk of 1.8 in the relatives
{1029}. When the breast cancer was of
early onset (diagnosed before age 50),
the relative risk among first-degree relatives
increased to 2.6 and the risk for
early-onset breast cancer among these
relatives was 3.7 (95% CI. 2.8—4.6). The
risk to subsequent relatives in families
with two affected sisters was increased
to 2.7 with a particularly high risk of 4.9
of early onset breast cancer. A second
registry-based study in Sweden found
essentially identical results to the Utah
study {715}.
Perhaps the largest population-based
study (the Cancer and Steroid Horm o n e
(CASH) case-control study) of probands
with breast cancer diagnosed
between the ages of 20 and 54 estimated
the risk of breast cancer in firstd
e g ree relatives compared with cont
rols was 2.1 {501}.
A study of cancer at a number of sites
in a large set of twins in Scandinavia
{1658}, estimated the pro p o rtion of variance
due to genetic (heritability),
s h a red environment, and random (individual-specific)
environmental eff e c t s
for each cancer site. Based on this
data, the authors calculated a co-twin
relative risk of 2.8 in DZ and 5.2 in MZ
twins, and estimated that 27% of bre a s t
cancer is due to inherited cause while
only 6% could be attributed to share d
e n v i ronment.
The role of other factors with respect to
family history has been examined.
Larger familial effects among relatives of
young bilateral probands compared with
young probands with unilateral bre a s t
cancer have been found {93,1246,2129}.
The relationship of histology to familial
b reast cancer is less clear {500,2989}.
Another feature, which conveys stro n g
familial risk of breast cancer, is the
o c c u r rence of breast cancer in a male. It
has been estimated that female re l a t i v e s
of probands with male breast cancer
have a two-fold to three-fold incre a s e d
risk of breast cancer {94,2449}.
Familial associations of breast and other
cancers
A number of studies have found increased
risks for other cancers among
relatives of breast cancer probands. The
most commonly reported are ovarian,
uterine, prostate and colon cancers. In
Table 1.10
Estimates of relative risks for breast cancer.
Relative affected, status of proband Estimate of relative risk {Reference} (Study Type)
Mother 3.0 {1321a} (a)
Sister 3.0 {1321a} (a)
Mother 2.0 {2214} (a)
Sister 3.0 {2214} (a)
Sister, premenopausal proband 5.0 {92a} (b)
Sister, postmenopausal proband 2.0 {92a} (b)
First-degree relative (FDR) 2.0 {346a} (c)
Sister, bilateral proband 6.0 {2129} (c)
Sister 2.0 {412a} (d)
Mother 2.0 {412a} (d)
First-degree relative (FDR) 2.0 {2556a} (a)
FDR45 1.5 {2556a} (a)
First degree relative 2.1 {501} (c)
First degree relative, proband 55 1.6 {1246} (a)
FDR, bilateral proband 6.4 {1246} (a)
First degree relative 2.3 {2720a} (c)
Second degree relative 1.8 {2720a} (c)
First degree relative 1.8 {896} (a)
FDR