Breast cancer in a transitional society over 18 years: trends and present status in Shanghai, China.

As a metropolis with rapid social and economic development over the past three decades, Shanghai has a breast cancer incidence that surpasses all other cancer registries in China. In order to estimate the regular changing patterns of female breast cancer in urban Shanghai, population-based incidence data from 1975 to 2004 were studied. In addition, a one-hospital-based in-patient database of 7,443 female breast cancer patients treated surgically between January-1990 and July-2007 were reviewed, retrospectively. We observed that breast cancer incidence increased dramatically over the past 30 years and documented a peak incidence represented by the middle-age group (45-59 years), which emerged in the last 20 years. The incidence peak moved from the 40-44 year group in the previous two decades to the 50-54 year group in the most recent decade. Median age at diagnosis was earlier in Shanghai than in the western countries, although it increased from 47.5-year in 1990 to 50-year in 2007. Considerably higher exposure to reproductive risk factors and relatively fewer hormone-dependent cases were observed. The proportion of asymptomatic cases detected by screening gradually increased, as well as that of early-stage cases (from 78.6% in 1990 to 93.3% in 2007) and carcinoma in situ (14.7% in 2007). Analysis of surgical treatment patterns suggested a trend of less-invasive options. Both age of peak incidence and median age at diagnosis increase with time, which suggests that increased incidence trending along with increasing age, will be observed in the future. Consequently, specific screening protocol should be refined to consider birth cohorts.