Value of Quantitative SPECT/CT Lymphoscintigraphy in Improving Sentinel Lymph Node Biopsy in Breast Cancer

Introduction: Sentinel lymph node biopsy (SLNB) has been widely accepted as the standard procedure to assess the axillary lymph node status in breast cancer. However, more than 70% of excised sentinel lymph nodes(SLNs) have been found to be healthy. It may lead to unnecessary excisions and increase the incidence of postoperative complications. The aim of this study was to investigate the value of quantitative Tc-99m sulfur colloid(^99mTc-SC) single-photon emission computed tomography/computed tomography (SPECT/CT) imaging in avoiding excessive removal of unnecessary SLNs in breast cancer patients.

Methods: We retrospectively enrolled breast cancer patients who underwent ^99mTc-SC SPECT/CT imaging prior to SLNB. Clinical characteristics affecting the number of SLNs detected were analyzed. Radiotracer uptake in SLNs was quantified from SPECT/CT data. A radioactivity count threshold using SPECT/CT for differentiating metastatic SLNs was calculated and expressed as R_SPECT. To localize SLNs exactly, we compared the positions of SLNs localized by preoperative SPECT/CT with those localized surgically by intraoperative γ-probe.

Results: A total of 1504 SLNs were excised from 491 consecutive patients. Three or more SLNs/patient were detected intraoperatively, especially in patients with a history of prior excisional biopsy. SPECT/CT identified SLNs in 82% of patients, with a median of two SLNs/patient and more SLNs in patients ≤50 years old. As the number of SLNs visualized on SPECT/CT images, the metastasis incidence of SLN in the ≤2 SLNs group was significantly higher than that in the >2 SLNs group (35% vs. 15%, P<0.001). No metastasis was found in lymph nodes with R_SPECT≤30% in the >2 SLNs group. The positions of SLNs localized by SPECT/CT were identical in 42% (39/93) of patients.

Conclusions: Quantitative ^99mTc-SC SPECT/CT imaging has the potential to preoperatively locate SLNs and intraoperatively avoid unnecessary SLNB, particularly in younger patients or those with prior excisional biopsy.