Background: Dual localization methods with blue dye and radioisotope are commonly employed for SLN identification but potential drawbacks include allergic reactions, radiation exposure and mandatory licencing. Identification rates exceeding 95% have been reported using the fluorescent tracer indocyanine green (ICG) as a navigation system. A feasibility study was undertaken to confirm the sensitivity and safety of ICG as a tracer agent for sentinel lymph node (SLN) identification in early breast cancer.

Methods: In an open, non-randomised study, 100 clinically node negative patients (95 unilateral; 5 bilateral) scheduled to undergo routine SLN biopsy for core-biopsy proven invasive breast cancer were identified at the multidisciplinary team meeting [53 screen-detected; 51 symptomatic]. All patients received triple localization with blue dye (2.5% Patent Blue), radiocolloid and ICG (0.5%). The number of sentinel nodes for each patient were recorded numerically and whether blue, radioactive or fluorescent. Subcutaneous lymphatics were visualized with a Photodynamic Eye camera and sensitivity of individual tracers alone and in combination calculated. Approval was granted by the Local Research Ethics Committee and the Medicines and Healthcare Products Regulatory Agency for use of ICG as a third tracer agent.

Results: Final analysis was performed on 104 procedures in 99 patients (1 exclusion - benign adenomyoepithelioma on definitive pathology). A total of 242 nodes were removed of which 201 were defined as sentinel (blue and/or radioactive) with an average nodal retrieval of 2.33 per procedure. Amongst these, 25 contained either macrometastases (n = 16) or micrometastases (n = 9), yielding procedural and node specific positivity rates of 17.3% (18/104) and 12.4% (25/201) respectively. 100% of these ‘true’ SLNs were fluorescent (201/201), 95.0% (191/201) were both fluorescent and blue, 77.6% (156/201) were fluorescent and radioactive whilst 73.1% (147/201) were blue, radioactive and fluorescent. The procedural detection rates were 99% (103/104) for blue dye, 91.3% (95/104) for radioisotope and 100% for fluorescence. All 25 positive nodes were identified with all three tracers and all 18 node positive patients had tumour deposits in the first SLN excised. The majority of ‘non-sentinel’ nodes were fluorescent (36/41) and no serious adverse reactions occurred.

Conclusion: ICG fluorescence imaging permits real-time visualization of lymphatics and provides an additional dimension to SLN biopsy which is safe and effective. These results confirm high sensitivity for fluorescence in SLN identification and the combined nodal sensitivity for ICG and blue dye (95.0%) was higher than for blue dye and radioisotope (73.1%). With further refinements in the technique may it may be possible to eventually rely on ICG as a sole tracer agent. Moreover, a marginally higher nodal yield with fluorescent mapping may allow more confident omission of completion axillary dissection in selected SLN positive patients.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P1-01-01.