Clinical application of noninvasive and nonradioactive determination of microscopic lymph node tumor status by multispectral optoacoustic imaging

412 Objectives Melanoma is a growing interdisciplinary public health challenge worldwide. Sentinel lymph node excision (SLNE) is a valuable diagnostic procedure recommended in the current AJCC guidelines. However it does represent a radioactive, cost-intensive intervention with morbidity not offering patients any advantage in overall survival. Excluding metastasis in draining lymph nodes by noninvasive imaging could spare many patients a SLNE. Multispectral optoacoustic tomography (MSOT) could help overcome the diagnostic drawbacks of SLNE using its potential to detect and stage SLNs noninvasively utilizing nonradioactive tracer. Methods In a prospective cross-sectional study in 80 patients a hybrid ultrasound/MSOT-guided ICG-based SLN detection followed by MSOT determination of SLN status was directly compared to standard 99mTc-guided SLNE and conventional pathological analysis of the SLNs. Results Hybrid ultrasound/MSOT imaging combined with the near-infrared fluorophore indocyanine green reliably visualized SLNs in vivo in 80 patients, up to 5-cm penetration and with 100% concordance with 99mTc-marked SLN lymphoscintigraphy. MSOT identified cancer-free SLNs in vivo without a single false negative (137 total lymph nodes), with 100% sensitivity and 48.6% specificity. Conclusions We present a novel, noninvasive strategy, which has a high potential to eliminate the complex, radioactive and invasive SLN procedure for a significant number of melanoma patients.