Oncoplastic versus standard breast-conserving surgery for extensive ductal carcinoma in situ: a retrospective cohort study of lesions 4 cm or larger treated 1995–2018

Background: The management of large-volume ductal carcinoma in situ (DCIS) is challenging, and evidence comparing standard breast-conserving surgery (S-BCS) with oncoplastic breast-conserving surgery (O-BCS) is limited. This study aimed to compare surgical and oncological outcomes of O-BCS and S-BCS in patients with large-volume DCIS treated at a single specialist breast unit.

Methods: This retrospective cohort study included patients with DCIS measuring 4 cm or greater who underwent initial breast-conserving surgery (BCS) at the Nottingham Breast Institute (NBI) between 1995 and 2018. Demographic, operative, pathological, and outcome data were analysed. Primary outcomes included BCS success, margin status, re-excision, conversion to mastectomy, local recurrence, and survival. Fisher’s exact tests, independent samples t-tests, and multivariable logistic regression were used for group comparisons. Recurrence-free survival (RFS) and overall survival (OS) were evaluated using Kaplan-Meier analysis with log-rank testing.

Results: A total of 139 patients were included: 94 underwent S-BCS and 45 underwent O-BCS. The mean follow-up was 6 years. O-BCS achieved a significantly higher rate of negative margins than S-BCS (73.3% vs. 23.4%, P<0.001) and a markedly lower conversion-to-mastectomy rate (17.8% vs. 72.3%, P<0.001). Among breast-conserved patients, re-excision to clear margins was required significantly less often after O-BCS (8.1% vs. 65.4%, P<0.001). On multivariable analysis, O-BCS remained an independent predictor of BCS success after adjustment for age and tumour size [odds ratio (OR) 12.40, 95% confidence interval (CI): 5.18–33.19, P<0.001]. Subgroup analysis of patients with lesions greater than 5 cm demonstrated consistent advantages for O-BCS. In survival analyses included for descriptive purposes only, no significant difference in RFS (P=0.94) or OS (P=0.88) was detected between groups.

Conclusions: Oncoplastic techniques significantly improved margin clearance and reduced conversion to mastectomy compared with standard BCS in patients with DCIS measuring 4 cm or greater. No significant difference in recurrence-free or OS was observed, although interpretation was limited by sample size, follow up completeness and available survival data. These findings suggest that oncoplastic techniques can facilitate breast conservation in selected patients with extensive DCIS.