Futility of imaging to stage melanoma patients with a positive sentinel lymph node

The use of staging imaging in melanoma patients with a positive sentinel lymph node (SLN) has been reported to be of limited value. Improved accuracy resulting from the development of time-of-flight positron emission tomography (PET) and ongoing image quality improvement of computed tomography (CT) may challenge this statement. Our retrospective study assessed the clinical value of routine staging CT and PET/CT imaging in a recent cohort of asymptomatic SLN-positive patients. Between January 2011 and April 2014, 143 patients with a positive SLN were routinely staged using CT of various parts of the body or whole-body PET/CT. Scores were assigned for level of certainty for regional or distant metastases and incidental second primary malignancies. Diagnostic test performance was assessed, as well as the number and nature of ensuing additional diagnostic actions. CT was performed in 102 of 143 (71%) patients and PET/CT in 41 (29%) patients. The use of PET/CT increased over the study period. Metastases were found in two of the 143 patients (true-positive yield 1.4%). Sensitivity, specificity and positive predictive value were 11, 73 and 4% for CT and 17, 57 and 6%, respectively, for PET/CT. None of the 143 patients had a change in AJCC stage. Two other primary malignancies were found. Twenty-one (15%) patients were subjected to 37 additional investigations, referrals or procedures. Routine staging imaging with CT or PET/CT in SLN-positive patients is not useful. The yield is low and the results are often false positive, leading to unnecessary additional tests, most of which are costly and some potentially morbid.