Breast cancer in Hong Kong, Southern China: The population-based, ten-year analysis of epidemiological characteristics, stage-specific, cancer-specific, & disease-free survival in breast cancer patients: 1997–2006

Abstract

BACKGROUND: Breast cancer is the most common cancer and second leading cause of cancer death among women, after lung cancer in Asia. The age-standardized incidence rates of breast cancer in Hong Kong is 61.0 per 100,000 women, after Singapore and Taiwan. With such increase, it would be important to better understand breast cancer to guide health care professionals and health policy makers to plan clinical management. However, to date such information is still under-reported, this study provide a comprehensive ten-year analyses of breast cancer in Hong Kong. METHODS: A retrospective study on population database over 10-year obtained from Hong Kong Cancer Registry was performed. A total of 20,290 female breast cancers’ medical records, diagnosed between January 1, 1997 and December 31, 2006, were reviewed. Descriptive statistics were employed to describe the epidemiological, clinical, and diagnostic data. The prognostic information for diagnostic and pathological data of relative survival (RS) was estimated using the maximum likelihood approach with program Strel in STATA; while the overall survival (OS), cancer-specific survival (CSS) & disease-free survival (DFS) were estimated by the Kaplan-Meier method with SPSS. Chi-squared test and Student's t-test were employed to compare variables in the two 5-year-periods of 1997-2001 and 2002-2006, with plotted RS curves for diagnostic and pathological data between these two 5-year-periods. RESULTS: 18,110 invasive breast cancer medical records in 1997-2006 were eligible for analysis, after 2,180 cases were excluding due to incomplete data. The ages at diagnosis ranged from 16 to 105; and median age was 51 years old. There was a drop from 14.1% in 1997-2001 to only 10.6% in 2002-2006 for those were diagnosed with breast cancer at age 39 years & younger. 26.2%, 55.2%, 13.0%, & 5.6% in 1997-2001, versus 30.1%, 46.4%, 16.9%, & 6.6% in 2002-2006 had tumor staging of stages I, II, III, and IV cancers at diagnosis, respectively. In ten-year period, the 5-year OS, RS, CSS, & DFS for the whole cohort were 80.6%, 85.6%, 87.1%, & 90.5%, respectively. The 5-year tumor stage-specific RS were 97.8%, 90.4%, 70.4%, & 21.4% for stages I, II, III, & IV, respectively. Between the two time periods, all the stage-specific RS improved by about 1%, 4%, 6% & 2% for stages I, II, III, & IV, respectively. There were 2,670 (14.7%) triple negative cases in 1997-2006, the ER-positive, PR-positive, & HER2-positive cancers increased from 66.1%, 52.6%, & 25.5% in 1997-2001 to 72.0%, 57.1%, & 29.4% in 2002-2006, respectively. DISCUSSION: Comprehensive analyses of breast cancer with population database from the Hong Kong Cancer Registry were performed to provide detailed information of a baseline study cohort in Southern China for comparative studies with other Asian regions.