Imaging Melanoma

The role of noninvasive imaging in melanoma differs depending on the clinical circumstance. At diagnosis, no or very limited systemic imaging for tumor staging is performed if patients have no clinical evidence of metastatic disease to lymph nodes or systemically. However, imaging is increasingly used to guide radionuclide sentinel lymph node biopsy procedures, especially if complex drainage routes are expected such as in the head and neck where SPECT/CT can be valuable. Ultrasound can be used to assess and follow regional lymph nodes in patients in whom sentinel node biopsy is not successful or not performed. In higher-risk patients if there is tumor involvement in lymph nodes at sentinel node imaging, or clinically, more extensive whole-body imaging including CT, FDG PET/CT, and MRI of the brain are commonly performed. Surveillance with these methods at regular intervals is recommended by several groups for several years post diagnosis, though guidance varies and is based on the risk of recurrence. Imaging, especially with PET/CT, is often used to assess suitability for surgical resection. Treatment response assessments by imaging are performed at more frequent intervals related to the timing of the specific therapy. Special attention in imaging patients treated with immune checkpoint inhibitors is necessary. CT, MRI, and PET/CT can have pseudo-progression, where responding tumors can transiently grow in size and metabolic activity, as well as apparent number, before response occurs. A delay of 1–2 months before repeat imaging to confirm progression or response is often needed. Use of imaging in melanoma still requires careful assessment for appropriateness to assure avoidance of overuse and attendant radiation and economic costs. Noninvasive imaging is a crucial part of the management of melanoma at multiple time points across the history of the illness. As new therapies evolve, our understanding of the best imaging methods and timing of imaging will evolve as well.