Breast cancer risk assessment and risk distribution in 3,491 Slovenian women invited for screening at the age of 50; a population-based cross-sectional study

FIGURE 1.

Questionnaire content used for Slovenian International Breast Cancer Intervention Study (S-IBIS) evaluation tool score calculation

Factors affecting levels of endogenous hormones (menarche, menopause, first birth age).

Exogenous hormone intake (menopause hormone replacement therapy).

Anthropometric characteristics (height, weight).

Breast biopsy (done, not done, presence of atypia, atypical hyperplasia).

Family history of breast and ovarium cancer (mother, sisters, half-sisters, daughters, grandmothers, aunts, male relatives).

Ovarian cancer of the participants.

Number of screening mammographies among 3,491 women through their whole screening period (aged 50–69 years) in case of different screening scenarios

Risk category	Lifetime breast cancer risk		10-year breast cancer risk
	Age-based screening (current screening)17	Slovenian risk-based screening18	Age-based screening (current screening)17	PROCAS risk-based screening27
Low risk	–	–	11,860	4,744
Population risk	34,130	34,130	21,720	15,204
Moderately increased risk	770	1,540	1,190	1,190
High risk	10	20	140	280
Total	34,910	35,690	34,910	21,418

10-year and lifetime breast cancer risk frequencies in the study group (risk calculated with the Slovenian International Breast Cancer Intervention Study (S-IBIS) evaluation tool, breast density information included) (N = 3,491)

Risk category	Frequency (N)	Per cent (%)
10-year breast cancer risk
low	1,186	34.0
population	2,172	62.2
moderately increased	119	3.4
high	14	0.4
Lifetime breast cancer risk
population	3,413	97.8
moderately increased	77	2.2
high	1	0.03

Characteristics of study participants (n = 3,491)

	Frequency (N)	Per cent (%)
Family history: first-degree relatives with breast/ovarian cancer (mother, father, sisters, daughters)
positive (1 relative)	326	9.3
positive (2 or more relatives)	28	0.8
negative	2,854	81.8
unknown	283	8.1
Family history: second-degree relatives with breast/ovarian cancer (aunts, uncles, grandmothers, half-sisters)
positive (1 relative)	437	12.5
positive (2 or more relatives)	148	4.2
negative	2,552	73.1
unknown	354	10.1
Age (years) at menarche
< 13	1,138	32.6
13	940	26.9
> 13	1,339	38.4
unknown	74	2.1
Age (years) at first birth
< 25	1,570	45.0
25–28	736	21.1
29–34	659	18.9
35	191	5.5
nulliparous	335	9.6
unknown	0	0.0
Menopausal status
premenopausal	1,392	39.9
perimenopausal	632	18.1
postmenopausal	631	18.1
unknown	836	23.9
HRT usage
yes	286	8.2
no	3,123	89.5
unknown	82	2.3
Breast biopsy
no biopsy	3,123	89.5
biopsy (hyperplasia, atypical hyperplasia, LCIS)	21	0.6
biopsy (else)	44	1.3
biopsy (unknown result)	256	7.3
unknown if biopsy done	47	1.3
Breast density
BI-RADS a	215	6.2
BI-RADS b	1,802	51.6
BI-RADS c	1,410	40.4
BI-RADS d	34	1.0
unknown (no screening mammography)	30	0.9
BMI
< 19	48	1.4
19–25	1,165	33.4
> 25	1,336	38.3
unknown	942	27.0

Breast cancer risk categories for Slovenian women at the age of 50 and risk-based screening scenarios according to different protocols18,24,26

Breast cancer risk category	Lifetime risk	10-year risk	Slovenian risk-based screening guidelines18,25	PROCAS study protocol27
Low risk (%)	**	< 1.3	**	5-year mammography screening interval
Population risk (%)	< 16	1.3–3.9	2-year mammography screening interval	3-year mammography screening interval
Moderately increased risk (%)	16–30	4.0–6.5	1-year mammography screening interval	2-year mammography screening interval
High risk (%)	> 30	> 6.5	1-year mammography screening interval	1-year mammography screening interval