The Added Value of a Single-photon Emission Computed Tomography-Computed Tomography in Sentinel Lymph Node Mapping in Patients with Breast Cancer and Malignant Melanoma

Abstract

Single-photon emission computed tomography-computed tomography (SPECT-CT) allows for physiological and anatomical co-registration in sentinel lymph node (SLN) mapping and offers additional benefits over conventional planar imaging. However, the clinical relevance when considering added costs and radiation burden of these reported benefits remains somewhat uncertain. This study aimed to evaluate the possible added value of SPECT-CT and intra-operative gamma-probe use over planar imaging alone in the South African setting. 80 patients with breast cancer or malignant melanoma underwent both planar and SPECT-CT imaging for SLN mapping. We assessed and compared the number of nodes detected on each study, false positive and negative findings, changes in surgical approach and or patient management. In all cases where a sentinel node was identified, SPECT-CT was more accurate anatomically. There was a significant change in surgical approach in 30 cases - breast cancer (n = 13; P 0.001) and malignant melanoma (n = 17; P 0.0002). In 4 cases a node not identified on planar imaging was seen on SPECT-CT. In 16 cases additional echelon nodes were identified. False positives were excluded by SPECT-CT in 12 cases. The addition of SPECT-CT and use of intra-operative gamma-probe to planar imaging offers important benefits in patients who present with breast cancer and melanoma. These benefits include increased nodal detection, elimination of false positives and negatives and improved anatomical localization that ultimately aids and expedites surgical management. This has been demonstrated in the context of industrialized country previously and has now also been confirmed in the setting of a emerging-market nation.

Keywords: Breat cancer; melanoma; sentinel lymph node; single-photon emission computed tomography-computed tomography.

Figure 1

Patient with left sided breast cancer. Planar transmission scan demonstrates a focus deemed to be the sentinel lymph node (a), which is shown to be artifactual (superficial to the skin) on single-photon emission computed tomography-computed tomography (b)

Figure 2

Patient with right-sided breast cancer. Two foci of tracer accumulation in noted on the transmission scan (a), however, single-photon emission computed tomography-computed tomography demonstrated that the inferior focus was in fact an area of tracer hold-up

Figure 3

Patient with right-sided breast cancer. The planar transmission scan demonstrates a single focus in close proximity to the injection site (a). Single-photon emission computed tomography-computed tomography allowed for better anatomical localization of this node (b) also demonstrated a second higher-echelon node located in the right supraclavicular region (c)

Figure 4

Patient with melanoma of the left scapular region. Shine through from the injection site on the silhouette images may be misleading. Furthermore no focus was demonstrated to suggest a sentinel lymph node (a). Single-photon emission computed tomography-computed tomography, however, demonstrated a superficial node in close proximity to the injection site (b)