The use of USPIO enhanced MRI in the assessment of axillary lymph node status in patients with invasive breast cancer

The prognosis of invasive breast cancer is reduced in patients with axillary
lymph node metastases. Staging of the axilla is nowadays performed by a
sentinel lymph node biopsy (SLNB). A positive SLNB is followed by axillary
lymph node dissection (ALND), a negative SLNB requires no further surgery. ALND
is an invasive procedure with severe morbidity in 10-20% of patients. Recent
evaluation of a new intravenous MR contrast agent (Ultrasmall,
SuperParamagnetic Iron Oxide nanoparticles, USPIO) has proved that lymph node
metastases can be visualised accurately in a non-invasive way.

Uspio enhanced MRI (MRL) potentially has the ability to show all lymph nodes
and hence provide information on metastasis in all nodes, this is in contrast
with SLNB which only provides information on 1 (or a few) lymph node(s). With
MRL metastases down to a size of 1 mm are detected.
In 38% to 62% of patients with a positive sentinel lymph node (SLN), the SLN is
the only positive node. ALND is performed in all these women and only
afterwards judged unnecessary. We expect MRL to be able to identify, with a
high negative predictive value, women who have no (further) involvement of
lymph nodes prior to SLNB or after a positive SLNB. Consequently ALND can be
withheld from these women. This saves morbidity and costs associated with ALND.
MRL may also prove valuable in the 4% of patients where localisation of the SLN
fails. All of these patients are now subjected to ALND. Use of MRL may prevent
this. Finally, because SLNB is false negative in 7-9% of patients, some
patients are inadequately treated. MRL has a high sensitivity and provides
information on all lymph nodes, consequently it may reduce the number of false
negative SLNB findings.

In patients with invasive breast cancer an USPIO enhanced MRI (MRL) will be
made prior to any surgical procedure to the axilla. The performance of MRL will
be controlled by ex vivo MRL of all surgical specimen, followed by a
node-to-node matching of all imaged nodes with pathology. Pathologic
examination of excised nodes will be regarded as the gold standard for
evaluation of node involvement. When the MRL is positive, but the SLNB is
negative no surgery will be performed but an image guided biopsy of affected
node(s) will be done and the pathologic examination of this biopsy will be used
as reference value.

Patients need to be at the hospital for administration of the contrast agent.
This will take approximately 30 minutes. Patients may complain of pain (usually
in the back) due to the administration of the contrast agent. Reduction of the
administration speed usually resolves this problem. There is also a minor risk
for allergic reactions and in a few cases anaphylactic reactions have been
described. Therefore medical observation is needed and will be performed during
1 hour after administration. This ensures adequate medical treatment in case of
emergencies.
Furthermore the MRI itself needs to be made. This requires the patient to be at
least 40 minutes inside the MRI-scanner. Although this is harmless, it may be
experienced as a burden, especially by people with mild claustrophobia. (Severe
claustrophobia is an absolute contra-indication).