LAUSR

In July 1903, at the Mack Avenue assembly plant in Detroit, the first automobile produced by the Ford Motor Company rolled off the line. Across the country, suppliers to the horse and buggy industry, then a dominant form of personal transportation, were generally unaware of this significant event. In Westfield, Connecticut, for example, over 40 buggy whip manufacturers were hard at work, while in Ohio, the Timken Company was producing roller bearings for carriage wheels. Just over a century later, Timken remains an industrial giant, relevant in numerous industries, with products in everything from surgical robots to rovers cruising the surface of Mars. Buggy whips? Not so much. In melanoma oncology, the genomic revolution and advent of effective systemic therapies are our Model Ts. It seems reasonable to ponder where sentinel lymph node (SLN) biopsy will be as melanoma care evolves. Continued relevance of the technique will depend on two things: demonstration of ongoing value, and innovation. SLN biopsy has had a dramatic impact on the accuracy of staging in melanoma, and the pathologic status of the SLN is one of the most powerful prognostic variables, independent of other known factors. Evidence supporting this statement is extensive and includes innumerable retrospective series, reviews of large prospectively maintained databases, meta-analyses, and multiple prospective clinical trials. The prognostic effect of SLN biopsy varies with other tumor characteristics, such as Breslow thickness, with the most dramatic effect being in the intermediate-thickness range, but it is also strongly supported for both thin and thick melanomas. SLN biopsy also appears to perform well relative to other less invasive technologies for nodal or prognostic assessment. Ultrasound, for example, has been used to evaluate regional nodes prior to SLN biopsy. Although it appears to be among the most sensitive imaging modalities for nodal evaluation, performance of ultrasound in the context of the second Multicenter Selective Lymphadenectomy Trial (MSLT-II) showed a sensitivity of only 6.6%, with modest improvements for patients with higher-risk primaries. Other diagnostic tools such as multispectral photoacoustic imaging have shown some promise in preclinical models but their sensitivity and specificity remain to be seen in large patient experiences. Gene expression profiling (GEP) is also being developed as a potential non-invasive staging tool in melanoma. It appears likely that these tests will be able to provide prognostic information independent of other current variables, but the data available for these tests at present lack sufficient granularity to know exactly what their role will be. Innovation and adaptation will be necessary for continued relevance of SLN biopsy, which will likely take place in several areas. In the current issue of Annals of Surgical Oncology, Carvalho and colleagues present an evaluation of fluorescence lymphatic mapping using indocyanine green (ICG). It was hoped that use of ICG might facilitate SLN biopsy without the need for radioactive tracers. Although there is little radiation exposure with the standard procedure, elimination of radiotracers could simplify several aspects of the process, including scheduling, specimen handling, and waste disposal. Unfortunately, the results of their prospective comparison of mapping agents Society of Surgical Oncology 2020