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14. Surgical Margins after Breast Conserving Surgery for Invasive Disease

Published: 10 July 2001

General Considerations

For most patients it is reasonable to try to achieve an ipsilateral breast tumour recurrence (IBTR) rate of  ¡Ü1% per year. The addition of a radiation boost to the tumour bed reduces the risk of IBTR. However, re-excision to obtain negative margins reduces IBTR more than using a radiation boost. The use of systemic therapy also reduces IBTR. For patients with a high systemic failure risk (for instance those with numerous positive axillary lymph nodes), it may be reasonable to accept a higher risk of IBTR. It may also be reasonable to accept a higher risk of IBTR in patients for whom further local breast surgery would result in an unacceptable cosmetic result, or where there is a strong desire to avoid a mastectomy, or if medical problems preclude surgery.

Guidelines for Re-excision and Radiation Boost following breast conserving surgery

1. For patients with invasive disease, invasive or in situ disease at the margin will be treated in the same manner.  
2. The definition of a negative margin is tumour > 2 mm from an inked margin.  
3. A positive margin is defined as tumour touching ink.  
4. A close margin is anything in-between.  
5. Re-excision to obtain negative margins is recommended for patients with close or positive margins.  
6. If a margin is < 2 mm and re-excision is declined or inappropriate, a radiation boost to the tumour bed is recommended.  
7. Re-excision should be more strongly recommended where the risk of IBTR is high and systemic risk is low, for example:

Margin < 2 mm and
extensive intraductal component present
age < 40
lobular histology
lymphatic invasion present
no systemic therapy given
margin close/positive at multiple sites
Margin status unknown
Tumour touching inked margin at any site

8. When the deep margin is positive, and the surgeon has dissected down to fascia, then a boost should be given.

Patients with close or positive margins who decline re-excision should be advised that the risk of IBTR is increased. The relative risks/benefits of re-excision vs boost in the context of local control and cosmesis should be discussed.

Timing of Re-excision

Early consultation with a radiation oncologist is recommended if there is uncertainty about whether or not re-excision is recommended. This will facilitate a timely re-excision. Generally, re-excision should be carried out as part of the definitive surgery and prior to adjuvant systemic therapy and radiation.

Lobular Carcinoma In Situ

Lobular carcinoma in situ at the margins does not constitute a positive margin.

Pathology Reports

If a pathology report does not contain the necessary information to determine margin status, then a BCCA pathology review should be obtained. If, after this, it is still not possible to accurately determine the margins, then the margins should be treated as unknown in which case a re-excision (or radiation boost) is generally recommended.