Early detection of breast cancer through population-based mammographic screening in Asian women: a comparison study between screen-detected and symptomatic breast cancers.

The first nation-wide mammographic screening program in Asia, BreastScreen Singapore (BSS), was launched in Singapore in January 2002. This study compared the presentation and results of screen-detected breast cancers with symptomatic breast cancers in two affiliated high-volume institutions, one of which was an assessment centre for BSS. The medical records of patients diagnosed with primary breast cancer at the Department of General Surgery, Singapore General Hospital and the Department of Surgical Oncology, National Cancer Centre, Singapore, during the period January 2002 to December 2003 were reviewed. Clinical and pathological comparisons were made between screen-detected lesions and symptomatic lesions. Of a total of 767 cases, 640 (83.4%) were invasive carcinomas and 127 (16.6%) were ductal carcinoma in-situ (DCIS) lesions. Only 13.4% of them were screen-detected. Compared to symptomatic cancers, screen-detected lesions were of smaller size (median size 18 versus 23 mm), a lower stage (stages 0-2, 95 versus 83.2%) and histologic grade (grade 1-2, 71 versus 60%), with a higher incidence of DCIS (31.0 versus 14.3%) and had higher rates of breast conservation (45.6 versus 28.2%) (all p-values <0.05). By multivariate analysis, tumor palpability, tumor size >20 mm, nodal involvement, cerbB2 overexpression, and advanced disease stage were independent poor prognostic factors for disease-free survival, whereas nodal involvement, advanced disease, and recurrence predicted poor cancer-specific survival. However, there was no statistically significant difference in disease-free survival or cancer-specific survival between the two groups at a median follow-up of 38 months. Screening mammography has allowed the detection of smaller and hence oncologically more favorable lesions in Asian women. Although no significant survival benefit was demonstrated in our study, a longer period of follow-up is essential before the benefit of mortality reduction, as a result of mammography screening becomes evident in our population.