Axillary Staging in Node Positive Breast Cancer Patients Receiving PST. SNB vs PET/MRI

The management of axillary nodes in breast cancer patients is a highly debated and evolving field. To date, an increasing number of patients with positive lymph nodes receives primary systemic therapy (PST) prior to surgery leading to down-staging axillary nodes in about 40% of women. However, the available diagnostic methods have several limitations in properly evaluating the response after treatment both in the breast and in the nodes and might lead to either under or over-treatment in these patients. Fully integrated scanners capable of simultaneous acquisition of PET and MRI have now been developed, with the potential to combine the specificity obtained by the functional imaging of PET, with the superior sensitivity of MRI, to provide higher diagnostic accuracy. It is expected that PET/MRI could better determine the response after PST to distinguish patients with negative versus patients with positive axillary nodes after medical treatment. As the excision of axillary nodes has mainly a staging purpose, the reliable identification of node negative patients might eventually spare women from unnecessary surgery. An accurate over-time and final imaging work-up might help choose the appropriate type of surgery according to the extent of nodal involvement: either SNB or complete axillary clearance.