Preoperative lymphatic mapping does not predict the number of axillary sentinel lymph nodes identified during surgery in breast cancer patients

Pre-operative sentinel lymph node localization in breast cancer with superparamagnetic iron oxide MRI: the SentiMAG Multicentre Trial imaging subprotocol

OBJECTIVE

Sentinel lymph node biopsy (SLNB) with a superparamagnetic iron oxide (SPIO) tracer was shown to be non-inferior to the standard combined technique in the SentiMAG Multicentre Trial. The MRI subprotocol of this trial aimed to develop a magnetic alternative for pre-operative lymphoscintigraphy (LS). We evaluated the feasibility of using MRI following the administration of magnetic tracer for pre-operative localization of sentinel lymph nodes (SLNs) and its potential for non-invasive identification of lymph node (LN) metastases.

METHODS

Patients with breast cancer scheduled to undergo SLNB were recruited for pre-operative LS, single photon emission CT (SPECT)-CT and SPIO MRI. T1 weighted turbo spin echo and T2 weighted gradient echo sequences were used before and after interstitial injection of magnetic tracer into the breast. SLNs on MRI were defined as LNs with signal drop and direct lymphatic drainage from the injection site. LNs showing inhomogeneous SPIO uptake were classified as metastatic. During surgery, a handheld magnetometer was used for SLNB. Blue or radioactive nodes were also excised. The number of SLNs and MR assessment of metastatic involvement were compared with surgical and histological outcomes.

RESULTS

11 patients were recruited. SPIO MRI successfully identified SLNs in 10 of 11 patients vs 11 of 11 patients with LS/SPECT-CT. One patient had metastatic involvement of four LNs, and this was identified in one node on pre-operative MRI.

CONCLUSION

SPIO MRI is a feasible technique for pre-operative localization of SLNs and, in combination with intraoperative use of a handheld magnetometer, provides an entirely radioisotope-free technique for SLNB. Further research is needed for the evaluation of MRI characterization of LN involvement using subcutaneous injection of magnetic tracer.

ADVANCES IN KNOWLEDGE

This study is the first to demonstrate that an interstitially administered magnetic tracer can be used both for pre-operative imaging and intraoperative SLNB, with equal performance to imaging and localization with radioisotopes.

Discordance between number of scintigraphic and perioperatively identified sentinel lymph nodes and axillary tumour recurrence

BACKGROUND

In breast cancer, sentinel node biopsy is considered the standard method to assess the lymph node status of the axilla. Preoperative identification of sentinel lymph nodes (SLN) is performed by injecting a radioactive tracer, followed by lymphoscintigraphy. In some patients there is a discrepancy between the number of lymphoscintigraphically identified sentinel nodes and the number of nodes found during surgery. We hypothesized that the inability to find peroperatively all the lymphoscintigraphically identified sentinel nodes, might lead to an increase in axillary recurrence because of positive SLNs not being removed.

METHODS

Patients who underwent sentinel node biopsy between January 2000 and July 2010 were identified from a prospectively collected database. The number of lymphoscintigraphically and peroperatively identified sentinel nodes were reviewed and compared. Axillary recurrences were scored.

RESULTS

1368 patients underwent a SLN biopsy. Median follow up was 58.5 months (range 12-157). Patient and tumour characteristics showed no significant differences. In 139 patients (10.2%) the number of radioactive nodes found during surgery was less than preoperative scanning (group 1) and in 89.8% (N = 1229) there were equal or more peroperative nodes identified than seen lymphoscintigraphically (group 2). In group 1, 0/139 patients (0%) developed an axillary recurrence and in the second group this was 25/1229 (2.0%) respectively. No significant difference between groups regarding axillary recurrence, sentinel node status and distant metastasis was found.

CONCLUSION

Axillary recurrence rate is not influenced by the inability to remove all sentinel nodes during surgery that have been identified preoperatively by scintigraphy.

Sentinel node biopsy for breast cancer patients: issues for discussion and our practice

Sentinel node biopsy has been established for several years now as a standard procedure of breast cancer surgery, but there are several variations of the indications and the technique used. This paper provides information regarding several issues of debate for its application as are the selection criteria, the application to patients with multifocal/multicentric breast cancer or DCIS, postneoadjuvant chemotherapy, the necessary number of nodes to be biopsied, the need for lymphoscintigraphy, the technique for frozen section, the factors that may predict nonsentinel nodes (NSNs) involvement, the value of micrometastasis and isolated tumour cells, the internal mammary chain sentinel nodes, and finally the axillary recurrence after SLNB. Our view for these issues is included together with our experience of 430 SLNBs.