Clinical outcomes of patients with ductal carcinoma in situ in Hong Kong: 10-year territory-wide cancer registry study

Background: Incidence of ductal carcinoma in situ (DCIS) has increased in recent decades because of breast cancer screening. This study comprised a long-term survival analysis of DCIS using 10-year territory-wide data from the Hong Kong Cancer Registry. Methods: This study included all patients diagnosed with DCIS in Hong Kong from 1997 to 2006. Exclusion criteria were age <30 years or years, lobular carcinoma in situ, Paget's disease, and co-existing invasive carcinoma. Patients were stratified into those diagnosed from 1997 to 2001 and those diagnosed from 2002 to 2006. The 5- and 10-year breast cancer-specific survival rates were evaluated; standardised mortality ratios were calculated. Results: Among the 1391 patients in this study, 449 were diagnosed from 1997 to 2001, and 942 were diagnosed from 2002 to 2006. The mean age at diagnosis was 49.2 +/- 9.2 years. Overall, 51.2% of patients underwent mastectomy and 29.5% received adjuvant radiotherapy. The median follow-up interval was 11.6 years; overall breast cancer- specific mortality rates were 0.3% and 0.9% after 5 and 10 years of follow-up, respectively. In total, 109 patients (7.8%) developed invasive breast cancer after a considerable delay. Invasive breast cancer rates were comparable between patients diagnosed from 1997 to 2001 (n=37, 8.2%) and those diagnosed from 2002 to 2006 (n=72, 7.6%). Conclusion: Despite excellent long-term survival among patients with DCIS, these patients were more likely to die of breast cancer, compared with the general population of women in Hong Kong.