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

We retrospectively enrolled breast cancer patients who underwent SPECT/CT prior to sentinel lymph node biopsy. Quantification of radiotracer uptake from SPECT/CT data was performed. A radioactivity count threshold (R _SPECT) using SPECT/CT was calculated for detecting metastatic sentinel lymph nodes. To localize sentinel lymph nodes exactly, we compared the positions of sentinel lymph nodes localized using SPECT/CT with positions localized surgically using an intraoperative γ-probe.

491 patients were included, with a median of 3 sentinel lymph nodes/patient detected by the γ-probe and 2 sentinel lymph nodes/patient detected by SPECT/CT. As the number of sentinel lymph nodes visualized on SPECT/CT images, the metastasis incidence of lymph nodes 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, and thus, 30% (157/526) of SPECT/CT-identified nodes would avoid unnecessary removal. The positions of sentinel lymph nodes localized by SPECT/CT and γ-probe were identical in 42% (39/93) of patients.

Quantitative Tc-99 m SC SPECT/CT imaging has the potential to preoperatively locate sentinel lymph nodes and intraoperatively avoid unnecessary sentinel lymph node biopsy.