Evaluation of the Upper Limb Lymphatic System: A Prospective Lymphoscintigraphic Study in Melanoma Patients and Healthy Controls
The prospective controlled trial satisfied us, because we have been questioning the value of lymphoscintigraphy with regard to reliability for detecting abnormal lymph circulation. Although lymphoscintigraphy is widely used as the gold standard for lymphedema evaluation, we have seen many cases where lymphoscintigraphy cannot detect abnormal lymph circulation in lymphedema patients (low sensitivity), and “abnormal” lymphoscintigraphic findings such as tracer transit delay are observed in normal control limbs (low specificity) as the study by Rossi et al. clarified.2,3 For lymphedema evaluation, high sensitivity and specificity are required, because many other conditions mimic lymphedema, and no symptom is manifested in subclinical or early lymphedema.2
As we have previously reported, indocyanine green lymphography can visualize superficial lymph flow very clearly in real time without radiation exposure.2–5 Although only superficial lymph flow can be visualized, indocyanine green lymphography allows accurate diagnosis and severity staging of lymphedema with higher sensitivity and specificity compared with lymphoscintigraphy, which enables precise evaluation of primary and secondary lymphedema of various body parts such as arm, leg, face, and genitals.2–5 Lymphoscintigraphy cannot allow accurate diagnosis of subclinical and early lymphedema because of its poor visualization of early changes of lymph circulation. In contrast, indocyanine green lymphography allows precise diagnosis and severity stratification of subclinical and early-stage lymphedema with different prognoses: dermal backflow stage 0, with no dermal backflow pattern (no lymphedema); dermal backflow stage I, with mild dermal backflow pattern (splash pattern, subclinical lymphedema), and dermal backflow stage II, with moderate dermal backflow pattern (stardust pattern, early lymphedema).2,3,5 Although Rossi et al. did not use indocyanine green lymphography in their study, we are confident that indocyanine green lymphography would allow differentiation of findings between the study group and the control group.
Although useful for assessing deep lymph flow such as in abdominal and thoracic lymph circulation, lymphoscintigraphy cannot accurately assess peripheral lymphodynamics, especially at an early stage of lymphedema. Because early diagnosis and treatment is critical for control or cure of lymphedema, an imaging modality with high sensitivity should be used for follow-up of patients at high risk of lymphedema after cancer treatment. Although indocyanine green lymphography is considered one of the best modalities for early diagnosis and routine follow-up, there are several modalities with high accuracy for early diagnosis of lymphedema, such as magnetic resonance lymphography, computed tomography lymphography, and ultrasonographic lymphography; they may be more useful for early diagnosis compared with lymphoscintigraphy. It may be time to reconsider the gold standard for diagnosis of lymphedema, and further comparative studies are warranted to determine the best modality or the best combination for accurate evaluation of lymphedema.