Utility of routine PET/CT and MRI staging in patients with sentinel lymph node positive melanoma

Abstract

9071 Background: The utility of routine radiographic staging in sentinel lymph node (SLN) positive stage III melanoma is unclear. Although body computed tomography (CT) has proven unlikely to identify occult metastasis at the time of diagnosis, there is some suggestion that whole body positron emission tomography combined with computed tomography (PET/CT) may be more sensitive in the detection of clinically unsuspected metastatic melanoma. We evaluated the ability of routine PET/CT and brain MRI to detect occult metastatic disease at the time of diagnosis in patients with SLN positive stage III melanoma. Methods: All clinically node- negative patients with cutaneous melanoma and a positive SLN who completed staging with PET/CT from 2003 through 2008 were identified from a prospective, IRB-approved, single-institution database. Data were analyzed to determine the positive (PPV) and negative (NPV) predictive values of PET/CT in detecting occult metastatic disease. Results: 72 patients had a positive SLN and were staged with PET/CT and 61 with brain MRI. There were 41 men and 31 women. Median age was 55 years. Median Breslow depth was 2.50 mm. 5 patients were T1, 25 T2, 22 T3, and 20 T4. 46 % were ulcerated. MRI was negative in all 61 patients. PET/CT was interpreted as suspicious for metastasis in 8 patients (11%) and negative in 64 (92%). 6 (8%) of the suspicious PET/CT scans were subsequently proven to be negative for malignancy and 1 (1.4%) proven to be an incidental thyroid cancer. Only 1 patient (1.4%) was found to have metastatic melanoma, an in transit metastasis that was previously unrecognized. PPV was 13% and NPV 100% for PET/CT. No patients were found to have occult distant metastases by either brain MRI or PET/CT. Conclusions: Patients with SLN positive stage III melanoma are unlikely to have occult metastatic disease detected by PET/CT or brain MRI and should not have further therapy delayed to obtain imaging. These findings are consistent with prior reports of body CT alone and question the utility of routine staging with current imaging modalities in patients with SLN positive melanoma. Future research should be directed toward improved imaging techniques in order to detect early micrometastatic melanoma. No significant financial relationships to disclose.