The evaluation of the complementary role of pre and postoperative PET/CT fusion imaging in the detection of regional lymph node metastatic disease in malignant melanoma.

7560 Background: Although,the sensitivity of PET for detecting subclinical regional lymph node/s metastatic disease in malignant melanoma is reported to be high but recent studies undermine its role.,We evaluated the comparative role of 18F-FDG-PET/CT and lymphatic mapping (LM) in 55 (40M: 15F; mean age 53.32± 16.76 years) melanoma patients (stage IIA-V, mean Breslow depth = 3.46 ± 2.57mm; range 1.0mm- 12.0 mm, Clarks level III-V) having no evidence of regional lymph node metastatic disease. PET imaging was performed preoperatively in 46 and postoperatively in 9 patients respectively.,Preoperative lymphoscintigraphy (LS) detected 116 SLNs (average 2.10 SLN per patient) and demonstrated a single and multiple (2-5) drawing nodal basin in 16 and 39 patients respectively. Histologically, only 22% (26/116) of the nodes detected by LS/LM, were positive for malignant melanoma. Peoperative and postoperative PET imaging was true positive for 1 SLN each respectively. Additionally, PET demonstrated 1 more SLN postoperatively in the left knee. False PET positivity was demonstrated for 4 SLNs, 1 each in the axilla, submandibular region & 2 in the supraclavicular region, preoperatively. The other 2 false positive metastatic lesions were the primary tumor sites. The preoperative PET sensitivity was 4%, specificity 94%, PPV 17%, NPV 75% and diagnostic accuracy (DA) 71%. However, the isolated statistical analysis in 9 patients in whom PET imaging was performed postoperatively, revealed a sensitivity of 100%, specificity of 87.5%, PPV of 50%, NPV of 100% and DA of 89%. On the contrary, the preoperative LS and intraoperative LM had an overall sensitivity of 93%, specificity of 100%, positive predictive value (PPV) of 100%, negative predictive value (NPV) of 83% and DA of 95% for the detection of subclinical nodal metastases.,Postoperative PET imaging is a useful modality in localizing recurrent distant metastatic disease during the follow up of malignant melanoma patients. No significant financial relationships to disclose.