Objective To explore the application effect of breast-conserving surgery combined with postoperative radiotherapy in breast ductal carcinoma in situ. Methods A total of 64 patients with breast ductal carcinoma in situ admitted to the Fourth Medical Center of Chinese PLA General Hospital from January 2023 to April 2025 were selected as the research subjects, and they were divided into the control group and the observation group according to different treatment methods, with 32 patients in each group. The control group received breast-conserving surgery, and the observation group received breast-conserving surgery combined with postoperative radiotherapy. The plasma cytokine levels, aesthetic effect, complication rate, tumor recurrence and metastasis were compared between the two groups. Results The plasma levels of VEGF-C and TGF-β1 in the observation group at 3 days after operation were lower than those in the control group (P<0.05). There was no signiffcant difference in aesthetic effect between the two groups (P>0.05). There was no signiffcant difference in the incidence of complications between the two groups (P>0.05). The local tumor recurrence rate and metastasis rate in the observation group were lower than those in the control group (P<0.05). Conclusion Breast-conserving surgery combined with postoperative radiotherapy in the treatment of breast ductal carcinoma in situ can ensure safety and achieve good aesthetic effect. This regimen can effectively reduce the probability of local tumor recurrence or distant metastasis, and down-regulate the plasma levels of VEGF-C and TGF-β1 in patients.