Kefah Mokbel, Chair of Breast Cancer Surgery at the London Breast Institute and Honorary Professor at Brunel University London, shared on LinkedIn:
“Do we still need the 2-mm rule in DCIS?
An important new study in Journal of Clinical Oncology challenges one of the established principles of breast-conserving surgery for DCIS: the 2-mm margin threshold.
Nash et al. analysed patient-level data from 11,156 women with DCIS treated with breast-conserving surgery, with or without radiotherapy.
The finding is potentially practice-changing:
Among patients with negative margins, margins <2 mm were not associated with a significantly higher risk of ipsilateral recurrence compared with margins ≥2 mm after multivariable adjustment.
This remained the case across multiple clinically relevant subgroups and whether patients received radiotherapy or not.
The important exception was women younger than 50, in whom narrower margins were associated with increased recurrence risk.
Why does this matter?
Current guidelines – including European guidance – have embedded 2 mm as the preferred/adequate margin for DCIS, and this threshold can influence decisions to return to theatre for re-excision.
These patient-level data make us ask whether a universal numerical threshold is still the right approach.
If a patient has a negative margin of 1 mm or 1.5 mm, should she routinely undergo another operation simply to achieve ≥2 mm?
Or should margin decisions increasingly reflect age, tumour biology, disease extent, radiotherapy, endocrine therapy and the overall recurrence risk, rather than millimetres alone?
The study is retrospective, with a median follow-up of 66.6 months, so it should not by itself rewrite guidelines. But with more than 11,000 patients, it provides an important challenge to the evidence underpinning current practice.
Perhaps the next evolution in DCIS surgery is not defining an ever more precise ‘safe margin’, but moving from a fixed margin threshold to individualised risk assessment.
A paper that deserves discussion in every breast MDT.”
You can also read: C/Can Seed Grant Supports Research Into Delays in Breast Cancer Care in Rosario
