PREDICTIVE ROLE OF IMAGING IN SENTINEL LYMPH NODE DISSECTION FOR MELANOMA

Abstract

A retrospective study of 67 patients withmetastatic melanoma was performed toevaluate if imaging from lymphoscintigraphycould predict a higher miss rate if only themost radioactive node were removed.Following protocol for sentinel node biopsy,the surgeon resected all lymph nodescontaining radioactivity >10% of the mostradioactive node. A correlation was performedbetween the radioactive counts of the lymphnodes and the presence of metastases. Thepercentage of cases in which the most radioactivenode was negative for metastasis onpathology was calculated. Two nuclearmedicine physicians read the images fromlymphoscintigraphy specifically to determineif the first lymph node visualized became lessintense than other nodes on later images.Sensitivity, specificity, positive predictive value(PPV), and negative predictive value (NPV)were calculated. In 13 of 67 (19%) patients,the most radioactive lymph node was negativefor metastasis while a less radioactive nodecontained metastatic disease. Consensusreading by the nuclear medicine physiciansdetermined that in 9 cases, the first lymphnode visualized became less intense thananother lymph node on later images. Of the9 cases, 4 were true positive and 5 were falsepositive when correlated with intraoperativecount rate and pathology. Of the cases wherethe most radioactive node was not positive onhistopathology (n = 13), the consensus readingby the nuclear medicine physicians reported4 of them (31%). Imaging by lymphoscintigramhad a sensitivity 31%, specificity 91%,positive predictive value 44%, and negativepredictive value 85% for predicting whetherthe most radioactive lymph node at surgerywould be negative for metastasis at pathology.We conclude that in patients with melanoma,lymphoscintigraphy has high specificity andnegative predictive value but modest sensitivityand positive predictive value for detectingwhen the sentinel node will not be the mostradioactive lymph node during sentinel lymphnode dissection. These findings support thatdynamic imaging by lymphoscintigraphyhas a role in surgical planning but that theimaging protocol could benefit from furtheroptimization.