36 Are Positive Margins in DCIS a True Indication of Inadequate Surgery?

Background/Significance

According to the American Society of Breast Surgeons’ 2017 “Consensus Guideline on Breast Cancer Lumpectomy Margins,” margin status serves as a surrogate marker of residual disease in the breast and has an impact on a patient’s risk of in-breast tumor recurrence. Margins for pure ductal carcinoma in situ (DCIS) treated with lumpectomy and radiation should be 2 mm or more. Close margins (<1 mm) at the chest wall or skin do not necessarily mandate reexcision. The use of margin status and lumpectomy reexcision rates as a measure of quality is controversial and may not reflect tumor biology.

Materials and Methods

To explore this in our academic community hospital, we identified 213 women diagnosed with DCIS who underwent lumpectomy and had margins assessed for a 2-mm standard from 2015 to 2020 in a retrospective study.

Results

Of 213 DCIS patients, 38 (17.8%) underwent breast conservation treatment and had positive margins on their initial pathology. Of these, 23 (60.5%) underwent a reexcision of margins in which the margins were able to be cleared: 20 of the 23 patients (87%) were found to have no residual disease in their second specimen and 3 (13%) required at least 2 additional surgical excisions of margins to be cleared after their initial surgeries. Ten of the 38 patients (26.3%) with positive margins following lumpectomy elected to proceed directly to mastectomy. All 10 were found to have residual disease. Five (13.2%) patients with positive margins had residual disease that was unable to be cleared despite surgical attempts. Negative margins were achieved in 23 (82.1%) of the 28 patients who elected to conserve their breasts.

Conclusions

While there is a consensus that 2-mm margins in DCIS are ideal, the technique to evaluate those margins is not uniform and the decisions for assessing and excising margins are still unclear. Almost half of patients with “positive margins” had no residual disease on reexcision, and in 13.2% of patients, we were unable to obtain satisfactory margins. Clearly, we need to improve our pathological assessment of margins as we learn more about the biology of DCIS.