We know that ACOSOG Z0011 demonstrated this safety of omission of axillary dissection in patients having up front surgery who are clinically node negative with one to two positive sentinel nodes undergoing breast conserving surgery. Patients who had matted extracapsular extension or gross extracapsular extension were excluded from ACOSOG Z0011 but patients who had microscopic extracapsular extension, which is just some growth of the disease outside of the lymph node capsule were not analysed in ACOSOG Z0011. So at Memorial in 2010 we adopted Z0011 as standard practice and developed a prospective database for all of our patients managed according to Z0011.
From 2010-2017 we had 811 patients undergoing breast conserving surgery who were clinically node negative managed according to Z0011. There were 693 patients who had one to two positive nodes that were treated with sentinel node biopsy alone and about 30% of them had microscopic extracapsular extension and were treated with sentinel node biopsy alone. Our primary endpoint was to look at nodal recurrence rates and we demonstrated no isolated axillary failures in our cohort, whether there was extracapsular extension or not. The rates of nodal recurrence, any nodal recurrence which included association with either breast or distant recurrence as well, were not different between patients that had microscopic extracapsular extension or those that did not. We did notice that those that had microscopic extracapsular extension were more likely to be treated with nodal radiation therapy, about 40% of them were, but we still saw no difference in nodal recurrence in those patients.
The implications of this study are that before we had demonstrated that patients with microscopic extracapsular extension in the sentinel node had a higher likelihood of having additional positive nodes and particularly four more positive nodes when they had greater than 2mm of ECE. But in our study we demonstrated low rates of nodal recurrence in patients with MECE, we call that instead of microscopic extracapsular extension. So these patients can be safely treated without axillary lymph node dissection and we demonstrated low rates of nodal recurrence and therefore omission of axillary dissection in patients with microscopic extracapsular extension is safe.
Hopefully people will begin to adopt this, as we have at Memorial. You still have to use clinical judgement if someone has other high risk factors that make you more concerned for a significant burden of disease that you could move forward. But it’s important to know that these patients do not require axillary lymph node dissection and have low rates of nodal recurrence so hopefully it will be adopted soon.
