Characteristics and Behaviour of Screen-Detected Ductal Carcinoma in Situ of the Breast: Comparison with Symptomatic Patients

Breast cancer is the most common malignancy in Singapore women. Ductal carcinoma in situ (DCIS) is the putative, non-obligate precursor of the majority of invasive breast cancers. The efficacy of the Singapore breast-screening pilot project in detecting early stage breast cancer led to the launch of a national breast-screening programme, BreastScreen Singapore (BSS), in January 2002. In this study, we compared clinicopathological and immunohistochemical characteristics, as well as clinical outcomes, between screen-detected and symptomatic DCIS. The study cohort comprised 1202 cases of DCIS diagnosed at Singapore General Hospital from 1994 to 2010. Comparison of clinicopathological parameters, immunohistochemical results of ER, PR, HER2, CK14, EGFR, and 34βE12, and clinical outcomes was carried out between the 2 groups. Amongst 1202 cases, 610 (50.7%) were screen-detected and 592 (49.3%) were symptomatic DCIS. Screen-detected cases were smaller in size (P < 0.001), of lower nuclear grade (P = 0.004), and more frequently expressed ER (P < 0.001). Luminal A phenotype was more frequently observed in screen-detected DCIS, while triple-negative and HER2 phenotypes were more common in symptomatic DCIS (P < 0.001). The basal-like phenotype was also more frequent in symptomatic DCIS (P = 0.041). Mean and median follow-up was 99.7 and 97.8 months, respectively, with a maximum follow-up of 246.0 months. More symptomatic patients developed invasive recurrences compared to screen-detected patients (P = 0.001). A trend for better disease-free survival was observed in screen-detected patients (P = 0.076). Patients who were screen-detected experienced better overall survival than those with symptomatic DCIS (P = 0.007). Our data indicate a more favourable outcome of screen-detected DCIS patients confirming the role of BSS in early identification of this curable disease.