Radiopathological features predictive of involved margins in ductal carcinoma in situ.

INTRODUCTION Ductal carcinoma in situ (DCIS) usually manifests as microcalcification on mammography but may be uncalcified. Consequently, a quarter of patients undergoing excision of a presumed pure DCIS require further surgery to re-excise margins. Patients at highest risk of margin involvement may benefit from additional preoperative assessment. METHODS A retrospective review was carried out of patients treated for screen detected, biopsy proven DCIS in a single centre over a ten-year period (1999-2009). Logistic regression analysis identified factors predictive of need for further surgery to clear margins. RESULTS Overall, 248 patients underwent surgery for DCIS (low/intermediate grade: 82, high grade: 155) and 49 (19.8%) required further surgery. High grade disease was associated with greater mammographic extent (mean: 32mm [range: 5-120mm] vs 25mm [range: 2-100mm]), p=0.009) and higher incidence of mastectomy (38% vs 24%, p=0.034). Factors predictive of involvement of surgical margins necessitating further surgery included negative oestrogen receptor status (OR: 5.2, 95% CI: 2.1-12.8, p<0.001) and mammographic extent (odds ratio [OR]: 1.6, 95% confidence interval [CI]: 1.2-2.1, p=0.004). Once size exceeded 30mm, more than 50% of patients required secondary breast surgery for margins. CONCLUSIONS Reoperation rates for DCIS increase with preoperative size on mammography and negative oestrogen receptor status on core biopsy. Patients with these risk features should be counselled accordingly and consideration should be given to the role of additional preoperative imaging.