What resection margins are required for DCIS with a component of invasive disease?

The SSO-ASTRO-ASCO guidelines of 2016 on margin status for patients with tumors that are pure DCIS or predominantly DCIS requiring a minimum of 2 mm for those receiving RT were based on a meta-analysis of (mostly older) published studies, not individual patient data. Three much more recent studies found that patients with margins less than 2 mm did quite well.

The first, from Van Zee and colleagues, PMID 26366541 at Memorial Sloan-Kettering Cancer Center, found crude local failure rates of 10% (6/59) for patients with positive margins, 10% (27/271) for margins 2 mm or smaller, 7% (35/498) for margins 2-10 mm, and 9% (58/672) for margins wider than 10 mm, with median follow-up of 6.25 years (see their Table 2). Ten-year actuarial rates were 2...

Based on guidelines.

Once invasive disease there, negative margin is no tumor at ink margin.

For pure DCIS with RT, aim for 2 mm margin but not absolute as need to look at the global picture before planning reexcision. If margin less, would boost for sure.

For no RT even through RTOG aim for 3 mm, in practice use same as above (2 mm or more).

For patients with pure DCIS who will be receiving adjuvant RT, our practice is to follow the SSO-ASTRO-ASCO Consensus Guidelines (Morrow et al., PMID 27528719) with the goal of 2 mm or greater margins. Occasionally, patients with <2 mm margins will be discussed in a multidisciplinary manner and re-excision may not be recommended in the case of focally close (<2 mm) margins and/or patient co-morbidities resulting in an elevated risk of peri-operative morbidity. Although RTOG 9804 required a minimal margin width of 3 mm to ink, we utilize the same 2 mm or greater margin as above for patients who may elect to omit adjuvant RT after a discussion of the risks and benefits.

For patients with invasive disease with associated DCIS, we utilize the AS...

I follow a similar practice to Dr. @Dr. First Last. I thought that Drs. Pilewskie and Morrow wrote a nice article on this subject with a review - PMID 29338088.

Ultimately --

1. Invasive + DCIS, follow invasive margin guidelines. The biology of the invasive is the primary concern in this patient.
2. DCIS with microinvasion, use DCIS margin guidelines.
3. DCIS with no RT planned - "best" margin arguable. I personally utilize 2mm+.
4. DCIS with RT planned - there is a relative benefit to maintaining a 2mm margin and a small absolute benefit. However, NSABP used no ink on tumor; single-institution series [MSK/MDACC] show that <2mm are not inferior to wider margins, and possible small LC differences that do not impact life expectancy mean that this scenario...

In the RTOG 9804 DCIS study, we had three categories of margin width, 3mm-9mm, 10mm or greater, or “negative on re-excision.” All patients were stratified by those margin categories, and we found no relationship between local recurrence and margin width. So for a patient with pure DCIS, I accept the consensus definition of a negative margin being 2mm or greater.

For patients with invasive cancer, and a component of DCIS, I accept the definition reached by consensus of the American Society of Breast Surgeons, which is “no tumor on ink.” That definition was reached after an extensive literature review on margins, and likely also reflects the fact that most patients with invasive breast cancer are also getting some form on systemic therapy, in ...