Margins for Ductal Carcinoma Insitu (DCIS)

The margin width (distance between the edge of the DCIS and the inked margin):
- Reflects the completeness of excision and is an important determinant of local recurrence in DCIS:
  - Particularly for patients considering omission of radiotherapy after breast-conserving surgery
In 2016, the Society of Surgical Oncology and American Society of Radiation Oncology:
- Developed consensus guidelines regarding margins for DCIS
- These guidelines were based on:
  - A meta-analysis of 22 studies enrolling 4,660 women treated with partial mastectomy and radiation therapy:
    - There was a 64% reduction in local recurrence risk:
      - In patients with negative margins compared to those with positive margins
    - Margin thresholds ≥2 mm were associated with fewer local recurrences
For patients with positive margins:
- Either re-excision or mastectomy to achieve negative margins should be performed
For patients with close margins:
- Multiple factors should be considered:
  - The volume / extent of DCIS
  - Its distribution throughout a specimen
  - The volume of the excision
  - The volume of DCIS deemed close to the margin (focal or extensive)
- After review of pathology:
  - Re-excision and / or radiation boost should be performed
A post-excision mammogram:
- May be considered to rule out residual suspicious calcifications in the partial mastectomy operative bed for targeting during re-excision, and breast-conservation therapy may be re-attempted
- If the close margins are extensive:
  - Mastectomy may be indicated
References
Morrow M, Van Zee KJ, Solin LJ, et al. Society of Surgical Oncology-American Society for Radiation Oncology-American Society of Clinical Oncology consensus guideline on margins for breast-conserving surgery with whole-breast irradiation in ductal carcinoma in situ. Ann Surg Oncol. 2016;23(12):3801-3810.
Van Zee KJ, Subhedar P, Olcese C, Patil S, Morrow M. Relationship between margin width and recurrence of ductal carcinoma in situ: analysis of 2996 women treated with breast-conserving surgery for 30 years. Ann Surg. 2015;262(4):623-631.

Dunne C, Burke JP, Morrow M, Kell MR. Effect of margin status on local recurrence after breast conservation and radiation therapy for ductal carcinoma in situ. J Clin Oncol. 2009;27(10):1615-1620.