Sentinel Lymph Node Identification in Patients With Breast Cancer Using SPECT/CT

The status of axillary lymph node involvement is the best prognostic factor in patients with early stage breast cancer. In the past; removal of all of the axillary lymph nodes (axillary lymph node dissection, ALND) was often the preferred method of treatment. ALND, however, has significant short- and long-term morbidity, the most significant being lymphoedema. With the trend towards earlier detection and presentation of breast cancer, most patients do not have lymphatic metastases at diagnosis. In these patients, ALND is purely a diagnostic procedure, with no therapeutic benefit; besides the widespread use of breast conserving surgery, the staging procedure carries greater morbidity than the therapeutic procedure of the primary cancer. Sentinel lymph nodes (SLNs) are defined as the first lymph nodes in a tumor bed that receive lymphatic drainage directly from the primary tumor; accordingly these nodes are most likely to harbor metastasizing cancer cells along the path of lymph drainage of tumor tissues, if lymphatic metastasis does occur. SLN biopsy (SLNB) has been demonstrated to be an ideal option to accurately stage axillary nodal involvement in breast cancer; it is a minimally invasive technique for lymphatic staging. The accurate detection of the SLN is paramount for the success of the procedure. SLNB in patients with clinically node-negative breast cancer is a valuable procedure for nodal staging ,treatment selection guiding, and often spares patients from the potentially devastating side effects of ALND such as lymphedema while maintaining the curative effect of surgery. Although being an important element in identification of SLNs; interpretation of planar lymphoscintigraphy is hindered by the absence of anatomical landmarks in the scintigraphic image. Single photon emission computed tomography coupled with computed tomography (SPECT/CT) was introduced in lymphatic mapping with the goal to show more SLNs and to show them more clearly than is possible with planar lymphoscintigraphy to improve nodal staging. Besides providing functional scintigraphic information, it provides accurate anatomical localization. This advantage facilitates surgical exploration. SPECT/CT can detect additional nodes not visualized on planar images and is especially useful in visualization of SLN outside the axilla or nodes close to the injection site.