Mixed Invasive and Intraductal Breast Cancer: What Surgical Margin Is Good Enough?

This article is referred to by:

Does a Close Surgical Margin for Ductal Carcinoma In Situ Associated with Invasive Breast Carcinoma Affect Breast Cancer Recurrence?

Since the introduction of conservation in breast cancer surgery, what constitutes an adequate excisional margin has been controversial and, at times, arbitrary. At first, wider margins were requested to achieve acceptable rates of local relapse, at the expense of the cosmetic result and the frequent need for re-excision. With time though, it became knowledge that the very wide margins were not necessary and until recently a 2 mm margin was considered adequate for all types of breast cancer.

However, in the era of precise preoperative diagnosis, detailed histopathologic investigation and modern adjuvant radiotherapy, it was found that it was unnecessary to sacrifice even a minimal amount of healthy tissue that surrounds the tumor and a “no ink on tumour” strategy was introduced [1]. But this time not for every type of tumor; it was admitted that different types of breast cancer may have a different potential for local relapse and DCIS excision was left under the previous safe recommendation of 2 mm margin [2].

The above evidence has decisively affected relevant treatment guidelines with the Society of Surgical Oncology, the American Society for Radiation Oncology, the American Society of Clinical Oncology, the National Comprehensive Cancer Network and others adopting the new paradigm: for invasive breast cancer “no ink on tumour” is enough but for DCIS a more aggressive approach of a 2 mm margin is still deemed necessary.

Between the two, however, there is a gray zone where invasive and intraductal breast cancers coexist; and in the everyday practice this scenario is common. The width, however, of the margin that should be achieved in these cases is not clear. Should one stick with the safety of the 2 mm margin or avoid the unnecessary sacrifice of healthy tissue (with all the consequence in cosmesis and reoperations) and settle for the “no ink on tumour” guideline? Does the DCIS which has partially progressed to invasive cancer retain its local aggressiveness? Is the quantity or/and the location (periphery or not) of intraductal component within the malignant area important for the relapse potential? There are no answers to the above as the evidence is not conclusive, with some advocating a more conservative approach [1], while others reporting increased relapse rates after narrow-margin excisions [3].

This is exactly where the article by Kuru et al. comes to add to existing knowledge [4]. The authors went back up to nearly 10 years, identified the patients who had received breast conserving surgery, with no ink on tumor and split them into groups based on the type of cancer and the margin width: invasive cancer only with any margin; invasive cancer associated with DCIS with less than 2 mm margin; and invasive cancer associated with DCIS with margin 2 mm or more. After a median follow up of 56 months, there were four local recurrences evenly spread in the three groups: in the invasive only group there was one relapse in 188 cases; in the close margin group there was one relapse in 119 cases; and in the 2 mm or more margin group there were 2 relapses in 321 cases. Despite the retrospective nature of the study and the low numbers, it is reasonable to conclude that local relapses after breast conserving surgery for invasive breast cancer associated with DCIS removed with less than 2 mm margin but with “no ink on tumour” are low and comparable with those of purely invasive tumors removed with “no ink on tumour” or mixed tumors removed with wider than 2 mm margins. Another interesting finding is that the Extensive Intraductal Component is associated with close margins but not with increased risk for relapse if removed with “no ink on tumour”.

These results are not heretic. Despite not knowing all the details of underlying cancer biology and specifically local progression and spread, they are in accordance with the existing widely used guidelines, which highlight that the natural history, treatment and outcomes of breast cancers combining in situ and invasive components resemble rather invasive than intraductal lesions [5]. Given that current guidelines are based on clinical experience rather than randomized trials, every new piece of evidence on this matter is welcome.

Declaration of Interest

The author reports no conflict of interest. The author alone is responsible for the content and writing of the article.