Summary: Appropriate Use Criteria for Lymphoscintigraphy in Sentinel Node Mapping and Lymphedema/Lipedema

Expert representatives from 11 professional societies, as part of an autonomous work group, researched and developed appropriate use criteria (AUC) for lymphoscintigraphy in sentinel lymph node mapping and lymphedema. The complete findings and discussions of the work group, including example clinical scenarios, were published on October 8, 2022, and are available at https://www.snmmi.org/ClinicalPractice/ content.aspx?ItemNumber=42021. The complete AUC document includes clinical scenarios for scintigraphy in patients with breast, cutaneous, and other cancers, as well as for mapping lymphatic flow in lymphedema. Pediatric considerations are addressed. These AUC are intended to assist health care practitioners considering lymphoscintigraphy. Presented here is a brief overview of the AUC, including the rationale and methodology behind development of the document. For detailed findings of the work group, the reader should refer to the complete AUC document online.

SPECT/CT scans allow precise anatomical location of sentinel lymph nodes in breast cancer and redefine lymphatic drainage from the breast to the axilla

BACKGROUND

Historical studies of lymphatic drainage of the breast have suggested that the lymphatic drainage of the breast was to lymph nodes lying in the antero-pectoral group of nodes in the axilla just lateral to the pectoral muscles. The purpose of this study was to confirm this is not correct.

METHODS

The hybrid imaging method of SPECT/CT allows the exact anatomical position of the sentinel lymph node (SLN) in the axilla to be documented during pre-operative lymphoscintigraphy (LS) in patients with breast cancer. We have done this in a series of 741 patients. The Level I axillary nodes were defined as anterior, mid or posterior. This was related to the anatomical location of the primary cancer in the breast.

RESULTS

A SLN was found in the axilla in 97.8% of our patients. Just under 50% of SLNs located in the axilla were not in the anterior group and lay in the mid or posterior group of Level I axillary nodes. There was a SLN in a single node field in 460 patients (63%), two node fields in 261(36%), three node fields in 6 and four node fields in 1 patient.

CONCLUSION

Axillary lymphatic drainage from the breast is not exclusively to the anterior (or antero-pectoral) group of Level I nodes.

SYNOPSIS

SPECT/CT lymphoscintigraphy shows that the breast does not always drain to the anterior group of Level I lymph nodes in the axilla but may drain to the mid axilla and/or posterior group in about 50% of patients with breast cancer regardless of the location of the cancer in the breast. These data redefine lymph drainage from the breast to axillary lymph nodes.

Neuroblastoma and other neuroendocrine tumors

Neuroblastoma is the most common extracranial solid tumor of childhood. It commonly presents in children younger than 2 years of age, with 90% being younger than 5 years of age. There is marked variability in clinical behavior ranging from spontaneous regression or differentiation into benign tumors to rapid and progressive fatal disease. Approximately 50% of patients will have metastases at presentation. The management is dependent on age, stage of disease, and biological and biochemical markers. Nuclear medicine plays an important role in the initial staging, as a prognostic indicator, for assessment of response to treatment, and also in therapy. The most common nuclear medicine diagnostic studies are (99m)Tc-disphosphonate bone scintigraphy and (123)I-MIBG (metaiodobenzylguanidine) scintigraphy. Bone scintigraphy has been the main investigational modality to diagnose skeletal metastases. Whole body imaging with (123)I-MIBG has become the preferred diagnostic test because this agent accumulates in neuroblastoma in 90% to 95% of cases and will accumulate in the primary tumor and metastases particularly in bone, bone marrow, lymph nodes, and soft tissues. MIBG can be used to assess therapy response and is a significant prognostic indicator. Other diagnostic techniques include positron emission tomography (PET)/computed tomography, mainly using (18)F-fluorodeoxyglucose. Other more experimental PET agents, as well as radiolabeled antibodies and octreotide, also are being investigated. Therapy has mainly focused on palliation and has been used alone or in combination with chemotherapy in high-risk refractory or relapsed patients. Major attention is being placed on stratification of patients to try and reduce the side effects associated with intensive megatherapy in the low to intermediate risk patients. Neuroendocrine tumors (NETs) are rare in childhood, but nuclear medicine techniques, mainly using MIBG and somatostatin receptor agents, have a role in diagnosis, staging, and a limited role in therapy. Newer radiopharmaceuticals, including PET agents, are being evaluated for the assessment of NET. Nuclear medicine techniques play a major role in the management of neuroblastoma and NET.

The Reproducibility in Routine Clinical Practice of Sentinel Lymph Node Identification by Pre-operative Lymphoscintigraphy in Patients with Cutaneous Melanoma

Pre-operative lymphoscintigraphy (LS) is an important part of successful sentinel lymph node (SLN) biopsy in most melanoma treatment centers. The test accurately maps lymphatic drainage from cutaneous melanoma sites and has been shown to be reproducible in prospective studies. Its reproducibility has not been tested, however, in routine clinical practice. Occasionally, after LS has been performed to map the location of SLNs, the patient is unable to proceed to SLN biopsy surgery within the time limit imposed by the radioactive decay of the 99mTc label attached to the colloid particles. In this situation, the surgery is rescheduled and LS repeated to relabel the SLNs so that they may be accurately biopsied. This has happened on 21 occasions at the Sydney Melanoma Unit and we have performed a retrospective analysis of the reproducibility of the LS results. In 19 patients, the same SLNs were shown in the same locations on the two studies. Two patients had discrepant results. One showed two extra interval nodes on the back as well as concordant flow to SLNs in each axilla. The other with a leg melanoma showed the same groin SLNs but failed to relabel the two popliteal SLNs on the second study. SLN locations were identical during 95%, and SLNs were identical 94% of the time. These results indicate that in routine clinical practice LS is a highly reproducible procedure to locate and radiolabel the SLNs prior to biopsy in patients with melanoma.

The Role of Lymphoscintigraphy in the Detection of Lymph Node Drainage in Melanoma

Lymphatic drainage of the skin cannot be predicted based on clinical guidelines developed more than 100 years ago. Approximately 30% of patients experience drainage from the skin to unexpected lymph node sites rather than those specified by these guidelines, and therefore these outdated assumptions should no longer be used to plan surgery. A possible survival benefit has been shown for the early detection and surgical removal of metastatic disease in the draining lymph nodes, and therefore, clinicians must obtain accurate lymphatic mapping for each patient who has intermediate thickness melanoma to plan appropriate surgical therapy. Lymphoscintigraphy can be used to accurately define the precise position of each true sentinel node in every patient, whether these nodes lie in a standard node field or in an unusual location. In this way, lymphoscintigraphy has a direct beneficial impact on the surgical management of patients who have melanoma.