The LORIS trial is an ongoing phase III clinical trial on low risk ductal carcinoma in situ (DCIS). DCIS patients aged ≥46 years with screen-detected low/intermediate nuclear grade were considered low risk and were randomised into surveillance or standard surgery. Here we review the 10-year territory-wide breast cancer registry database and evaluate the clinical outcomes of low versus high risk DCIS patients. This was a retrospective study of a prospectively maintained territory-wide breast cancer registry in Hong Kong. Between 1997 and 2006, 1391 DCIS patients were identified from the Hong Kong cancer registry breast cancer database. The mean age at diagnosis was 49.2 years (range 30–70). In total, 372 patients were classified as ‘low risk’, whereas the remaining 777 patients were classified as ‘high risk’. After a median follow-up of 11.6 years, the 10-year overall breast cancer-specific survival of the entire DCIS cohort was 1136/1149 (98.9%). Overall breast cancer-specific survival of low risk DCIS was 99.5%, whereas that in high risk DCIS was 98.6% (Log-rank test, P = 0.208). Forty-six (12.4%) patients in the LORIS low risk group did not receive surgery, whereas 93 (12%) patients in the LORIS high risk group did not receive surgery. The 10-year breast cancer-specific survival in the non-operated low risk DCIS group was 97.8%; that in the non-operated high risk DCIS group was 96.7% (P = 1). Long-term survival of DCIS was excellent, especially in low risk DCIS, regardless of surgical treatment. •Incidence of ipsilateral invasive breast cancer event in patient with ductal carcinoma in situ (DCIS) was 759.4 in 100,000.•Incidence of subsequent invasive breast cancer in low-risk DCIS with or without surgery were comparable.•10-year overall breast cancer specific survival (BCSS) was 98.9%. Overall BCSS of LORIS-low risk and high-risk DCIS were comparable.•10-year BCSS in the non-operated low risk DCIS was 97.8%, and that in the non-operated high-risk DCIS was 96.7%.