"The Benefit Of Positron Emission Tomography/Computed Tomography In Stage I And Stage II Melanomas With High-Risk Decisiondx-Melanoma Scores".

Introduction: Early detection of melanoma is instrumental as the 5-year survival decreases from 93.3% to <50% when metastases are present. Distinguishing which patients require closer follow-up can be difficult for melanoma patients. Developments by Castle Biosciences' (Friendswood, TX) DecisionDx-Melanoma (DDx-M) use 31 melanoma associated genes to stratify melanomas into 4 classes with 1A having lowest risk of morbidity and mortality and 2B the highest. We assessed the benefit of providing additional FDG-PET-CT and brain MRI to genetically high-risk patients who may have otherwise been overlooked.

Methods: 297 patients at our institution had biopsies sent for DDx-M between 2014 and 2021. Patients found to have Class 2 melanomas received additional screening with yearly FDG-PET-CT scans and brain MRIs. Patients with Class 2 DDx-M scores and negative SLNB were included in the study. 66 met inclusion criteria and received imaging.

Results: Within 3 years of follow-up, 8/66 (12.1%) patients had metastases detected by FDG-PET-CT scans. No patients with stage IA or IB went on to develop metastases.

Discussion: FDG-PET-CT scans detect metastases in < 3% of the time when all stage I and II patients are scanned; however, by using DDx-M in our screening protocols, we achieved a detection rate of 12.1%. These patients went on to receive treatment and would have otherwise progressed undetected, leading to higher morbidity and mortality.

Conclusion: We suggest all patients with initial stage II or above melanomas receive a DDx-M score and those with class 2 receive yearly FDG-PET-CT/brain MRI imaging.