More than 190,000 people study: such women have a 137% increased risk of breast cancer!

▎WuXi AppTec content team editor

At present, the overall epidemiological characteristics of breast cancer in China include high incidence, low age of patients, high breast compactness and low screening rate
.
Breast density is one of the risk factors for breast cancer, and Asian populations have higher average breast density than Western populations, and some experts believe that breast density may be one of
the strongest known risk factors for breast cancer.

Recently, the International Journal of Cancer, an important journal in the field of oncology, published a blockbuster analysis study
.
Based on breast cancer screening data from nearly 190,000 women in Denmark, the study found that women with higher breast density (dense type) had a significantly increased risk of breast cancer by 137%
compared to women with lower breast density (fatty breasts).

Screenshot credit: International Journal of Cancer

Breast density can be classified in different ways, such as mammography density (PMD), mammary BI-RADS classification
.
Based on the BI-RADS grade, the mammary glands can be divided into 4 types:

• Fat type: breast gland tissue accounts for less than 25%;

• A small number of glands type: breast gland tissue accounts for 25%~50%;

• Multi-volume gland type: breast gland tissue accounts for 51%~75%;

• Dense type: more than
  75% of the breast gland tissue.
  

The current study conducted an in-depth analysis of the data of nearly 190,000 women in the Danish Capital Region screening program (women aged 50~69 who are screened every two years), and evaluated the incidence of breast
density-specific breast cancer.

A total of 189609 female subjects who were screened between November 1, 2012 and December 31, 2017 were included in the analysis, of which about 39% were 50~54 years old, 21% were 55~59 years old, 20% were 60~64 years old, and 21% were 65~69 years old
.
The mean follow-up time of participants was 5.
6 years (5.
9~6.
0 years in the 55~69 age group; 50~54 years old age group is 5.
2 years).

The results of the first screening showed that 33% of the participants included in the analysis had fatty glands, 38% had few glands, 24% were multi-gland, and 4.
7% were dense
.
During follow-up, a total of 4110 participants were diagnosed with breast cancer
.
Among them, the incidence rates of 50~54 years old, 55~59 years old, 60~64 years old and 65-69 years old were 302/100,000 cases, 358/100,000 cases, 469/100,000 cases and 466/100,000 cases
, respectively.

Image source: 123RF

The results of the analysis showed a significant increase
in the incidence of breast cancer in subjects with higher breast density compared with subjects with lower breast density (fatty breasts).
Specifically, the risk of breast cancer increased by 219%, 121%, 124% and 76% in the age groups of 50~54 years, 55~59 years old, 55~59 years old
, and 65~59 years old.

In addition, further analysis after adjusting for age in all age groups showed a 69% increased risk of breast cancer, a 106% increase in the risk of multiple glandular types, and a 137%
increase in dense subjects compared with fatty breast subjects.

Overall, the current study based on Danish large-scale population screening data confirmed that for subjects who started screening at the age of 50~64, the risk of breast cancer was significantly associated
with its breast density.
The overall risk of breast cancer can differ 2.
37-fold
between people with higher breast density (dense) and those with low breast density (fatty type).

The authors emphasized that if the biennial mammogram screening was also received from the age of 50, the cumulative risk of breast cancer in women with lower breast density was 6.
2%, while the cumulative risk of breast cancer in women with higher breast density could reach 14.
7%.