Shanghai has the highest incidence of breast cancer in the country, which can be linked to the city's low birth rate, health experts said.

The growth in the incidence of breast cancer in the city is double the world average. About 4,000 women are diagnosed with breast cancer every year in Shanghai.

The number of breast cancer patients in the country is expected to reach 2.5 million by 2021, according to the International Breast Cancer Forum held in Shanghai recently.

In China's urban areas, there are 34.3 breast cancer cases for every 100,000 women, twice that of rural areas, experts said.

"High incidences of breast cancer are mainly seen in first-tier areas, such as Beijing, Shanghai, Guangzhou and other coastal developed cities. This has a connection to local low birth levels," said Dr Shao Zhimin from the Shanghai Cancer Hospital of Fudan University.

The change of lifestyle and the decrease of breast-feeding due to the China's one-child policy also are seen as main reasons for the high incidence of breast cancer.

Shao's research team found that Chinese women between the ages of 45 and 55 and 70 and 74 are most likely to get breast cancer. In Western countries, the age of onset for women contracting the disease is mainly in the 60s and 70s.

Shao said a change in the age of onset will be seen soon with the recent relaxation of the one-child policy in China, which allows couples to have a second baby as long as one spouse comes from a one-child family.

"To give birth to a baby and have breast feeding is an important part of breast health," Shao said, adding that the peak age for Chinese women contracting the disease over the next 20 years will resemble that in Western countries.

GE Healthcare released a survey in October, which is Breast Cancer Awareness Month, which found that 50 percent of women in the world cannot recognize the most common symptoms of breast cancer.

The Value of Knowing global survey of 10,000 adults across 10 countries, including China, highlighted a significant lack of awareness about the risks associated with dense breast tissue. The dense tissue is found in about 40 percent of women.

Women with dense breast tissue have four to five times higher risk of developing breast cancer, yet only one out of five people in the world has seen, heard or read about dense breast tissue in the last six months, the report said.

"If a woman learns that she has dense breasts, it is important for her to talk with her healthcare provider about her risk and options for further imaging or management," said Susan Brown, managing director of Health and Science Education for Susan G. Komen, the world's largest breast cancer organization.

wanghongyi@chinadaily.com.cn