Lymphoscintigraphic sentinel node identification in patients with breast cancer: the role of SPECT-CT

Purpose: Lymph node status is a major factor in determining the stage, appropriate therapy and outcome in patients with breast cancer. It is therefore of clinical importance to accurately identify all sentinel nodes (SNs) for each individual tumour before surgery. The purpose of this study was to assess the role of SPECT-CT lymphoscintigraphy in SN identification in patients with breast cancer. Methods: Lymphoscintigraphy comprising planar and SPECT-CT acquisition was performed in 157 consecutive patients with breast cancer (mean age 54.7 +/- 10.6, range 27-81 years) with a palpable mass (n=100), with a non-palpable mass (n=52) or post lumpectomy (n=5). Planar and SPECT-CT images were interpreted separately and the two imaging techniques were compared with respect to their ability to identify hot nodes. Results: Planar imaging alone was negative for identification of hot nodes in 15% of the patients. SPECT-CT alone was negative in 10% and both techniques were negative in 9% of the patients. Forty-six of the total of 361 (13%) hot nodes identified by lymphoscintigraphy were detected only on SPECT-CT, including 21 nodes obscured by the scattered radiation from the injection site, nine adjacent nodes misinterpreted on planar images as a single node and 16 nodes which were missed on planar images and detected on SPECT data. SPECT-CT detected additional sites of drainage unexpected on planar images, including axillary (n=23 patients), internal mammary (n=5 patients), interpectoral (n=3 patients) and intramammary (n=2 patients) lymph node sites. Fourteen of the 329 (4%) hot lesions seen on planar images were false positive non-nodal sites of uptake that were accurately assessed by SPECT-CT and further validated by surgery. In a single patient, SPECT-CT was negative while planar images identified the SN. Conclusion: SPECT-CT may improve the preoperative localisation of draining nodes in patients with breast cancer. It may detect hot nodes missed by planar imaging, exclude non-nodal false positive sites of uptake and accurately localise axillary and extra-axillary nodes.