The aim of this work is to report the preliminary results of the Hungarian multicentric randomised DCIS study. Between 2000 and 2007, 278 patients with ductal carcinoma in situ (DCIS) treated by breast-conserving surgery were randomised according to predetermined risk groups. Low/intermediate-risk patients (n=29) were randomised to 50 Gy whole-breast irradiation (WBI) or observation. High-risk cases (n=235) were allocated to receive 50 Gy WBI vs. 50 Gy WBI plus 16 Gy tumour bed boost. Very high-risk patients (patients with involved surgical margins; n=14) were randomised to 50 Gy WBI plus 16 Gy tumour bed boost or reoperation (reexcision plus radiotherapy or mastectomy alone). Immunohistochemistry (IHC) was performed to detect the expression of potential molecular prognostic markers (ER, PR, Her2, p53, Bcl-2 and Ki-67). At a median follow-up of 36 months no recurrence was observed in the low/intermediate- and very high-risk patient groups. In the high-risk group, 4 (1.7%) local recurrences and 1 (0.4%) distant metastasis occurred. No patient died of breast cancer. In the high-risk group of patients, the 3- and 5-year probability of local recurrence was 1.1% and 3.1%, respectively. The positive immunostaining for Her2 (38%), p53 (37%) and Ki-67 (44%) correlated with a high nuclear grade. Significant inverse correlation was found between the expression of ER (77%), PR (67%), Bcl-2 (64%) and grade. Preliminary results suggest that breast-conserving surgery followed by radiotherapy yields an annual local recurrence rate of less than 1% in patients with DCIS. IHC of molecular prognostic markers can assist to gain insight into the biologic heterogeneity of DCIS.