How do we reconcile what appears to be a more aggressive surgical resection for DCIS than for invasive disease?

The guidelines panels did an outstanding job in generating both the DCIS and the invasive cancer margins guidelines. It needs to be recognized, however, that despite the sophisticated meta-analysis upon which the recommendations are based, the studies in the meta-analysis had limitations. Appropriately, the guidelines committee made the following statement in the DCIS guideline and also made similar cautionary remarks in the invasive guideline: "However, while the MP felt that there was evidence...

DCIS (or invasive cancers with an extensive DCIS component) appear to spread more widely inside the breast than purely or predominantly invasive cancers. Hence, the residual tumor burden following partial mastectomy is likely larger for the former group than the latter. This likely accounts for the apparent discrepancy between the ASTRO-SSO consensus guideline on the preferred margin width for patients with invasive cancer treated with partial mastectomy and RT (no tumor on ink) (Moran et al., P...

Great discussion and I agree with all of the comments. One item to emphasize is that pathologic assessment of the margin is a “very inexact science.” To the best of my knowledge, there is much variation in how aggressively the margins are assessed (e.g. shaved margins vs. slices taken orthogonal to the long axis of the specimen; slides taken every 1 mm vs 10 mm, etc.). All of these approaches have suboptimal utility due to the incredibly small volume of the specimen that is sampled; they/we are ...

There's also a medicolegal angle. If a patient with DCIS recurs and their margins were less than 2 mm, what is your defense when her lawyer asks you why you didn't follow the national guidelines that are based on multiple peer-reviewed trials? That, in your judgement, it wasn't necessary to follow national guidelines because you know better? That a few recent studies show a 2 mm margin wasn't necessary?

It won't take long for her lawyer to say, "Well, since her cancer came back whereas the vast ...