ESTRO 2024 - Abstract Book

S719

Clinical - Breast

ESTRO 2024

1 American University of Beirut Medical Center, Radiation Oncology, Beirut, Lebanon. 2 American University of Beirut Medical Center, General Surgery, Beirut, Lebanon. 3 American University of Beirut Medical Center, Internal Medicine, Beirut, Lebanon

Purpose/Objective:

Breast conserving surgery (BCS) followed by adjuvant radiation therapy (RT) is a standard treatment for ductal carcinoma in situ (DCIS). The presence of close (<=2mm) or positive margins is thought to be associated with a higher risk of local recurrence (LR). Patients with positive margins require re-excision. However, re-excision in the setting of close margins is debatable. This study aims to assess the re-excision rate and the incidence of residual disease in the re-excision specimen in patients diagnosed with DCIS with close or positive margins as well as disease outcomes.

Material/Methods:

In this retrospective study, records of adult patients, with histologically confirmed DCIS who underwent BCS, between august 2009 and August 2019 at our institution were identified. From a total of 166 patients, 57 were eligible for analysis; 35 had close margins and 22 had positive margins. Rate of re-excision and incidence of residual disease were calculated. Kaplan Meier curves for recurrence-free (RFS) and overall survival (OS) were generated. Regression analysis was used to analyze the association of re-excision with survival outcomes.

Results:

Among patients with close margins (n=35), 7 (21.2%) underwent re-excision that showed the presence of residual disease in 3 patients (42.9%). As for the 22 patients with positive margins, 17 (77.3%) underwent re-excision with the presence of residual disease in 6 patients (35.3%). For the entire cohort of patients with close or positive margins, 5-year and 10-year RFS was 94% and 85% respectively. 5-year and 10-year OS was 98% and 90% respectively. No significant association was found between the survival outcomes (RFS and OS) and re-excision in patients with close margins (p=0.658 for RFS and p=0.561 for OS) as well as patients with positive margins (p=0.499 for RFS and p=0.631 for OS).

Conclusion:

Our study shows a high rate of residual disease in re-excision specimens for patient with close or positive DCIS margins. Despite that, our cohort had a favorable RFS that was not associated with re-excision which is likely secondary to adjuvant RT. We agree that most experts would recommend re-excision for patients with positive margins. Larger studies are needed to better identify DCIS patients with close margins who might benefit from wider re-excision.

Keywords: DCIS, Positive or close margins, re-excision