PowerPoint Presentation Non-Invasive Genomic Profiling in Pediatric Patients Allyson G. Perry, PhD1, Danielle Ruppenthal, PA-C1, Kellie Hill, CLS (ASCP)1 Presented at the Winter Clinical Dermatology Conference January 13-18, 2023 1. DermTech, 11099 North Torrey Pines Road, Suite 150 La Jolla, CA 92037, USA 1. Gerami P, Yao Z, Polsky D, et al. Development and validation of a noninvasive 2-gene molecular assay for cutaneous melanoma. J Am Acad Dermatol. 2017;76(1):114- 120.e2. 2. Jackson SR, Jansen B, Yao Z, Ferris LK. Risk stratification of severely dysplastic nevi by non-invasively obtained gene expression and mutation analyses. SKIN The Journal of Cutaneous Medicine. 2020;4(2):105-110. 3. Tracy ET, Aldrink JH. Pediatric melanoma. Semin Pediatr Surg. Oct 2016;25(5):290- 298. References Funding/disclaimer: the authors are employed by DermTech. Conclusion Scan QR code for additional peer-reviewed publications regarding this genomic test While overall PLA positivity rates were similar across adult and pediatric samples, the proportion positive only for LINC was more than two times higher in pediatric samples than the adult samples. TERT promoter mutations are rare in lesions from pediatric patients. Further investigation of the significance of LINC, PRAME, and TERT abnormalities in lesions from pediatric patients is ongoing. Background: Pigmented lesions with clinical features suspicious for melanoma are not uncommon in pediatric patients. Evaluation of these lesions is complicated by the low prevalence of pediatric melanoma and challenges associated with performing biopsies in children. The DermTech Melanoma Test (‘the test’) is a non-invasive genomic test designed to rule out melanoma. It consists of the Pigmented Lesion Assay (PLA), which detects RNA gene expression of long intergenic non-coding RNA 00518 (LINC00518, or LINC) and preferentially expressed antigen in melanoma (PRAME), and an add-on assay for DNA promoter mutations in telomerase reverse transcriptase (TERT), which is performed if ordered and if sufficient genomic material is available. Patients younger than 18 years were not included in initial validation studies. In this analysis, we sought to compare genomic biomarker results between uncertain pigmented lesions from adult and pediatric patients. Methods: De-identified samples submitted to the clinical lab for the test from May through October 2022 were used for this analysis. Genomic results were available for 36,377 samples. The anatomic locations of the lesions were categorized as head/neck, trunk, or extremities and compared between adult and pediatric patients. Positivity rates for the PLA (and each individual marker) and the TERT add-on assay were calculated for adults and patients younger than 18 years of age. Results: The PLA was performed on 34,050 skin samples from adults and 2,327 samples from pediatric patients. There were no differences between adults and pediatric patients in anatomic location of the lesions tested. The proportion of PLA-positive samples was similar between adult (7.0%, n=2,393) and pediatric (8.0%, n=187) patients. Rates of biomarkers detected among PLA-positive adult and pediatric patient samples, respectively, were as follows: LINC only (31.4% vs 69.5%), PRAME only (45.5% vs 14.4%), LINC and PRAME (23.0% vs 16.0%). The TERT add-on assay was performed in 11,084 samples from adults and 613 samples from pediatric patients. Of these, TERT was positive in 830 (7.5%) adult and 3 (0.5%) pediatric patient samples. Conclusions: This analysis provides new information about genomic profiling of uncertain pigmented lesions from pediatric patients. While overall PLA positivity rates were similar across adult and pediatric samples, the proportion positive only for LINC was more than two times higher in pediatric samples. Additionally, TERT promoter mutations were rarely detected in pediatric samples. Further investigation of the significance of LINC, PRAME, and TERT abnormalities in lesions from pediatric patients is ongoing. Abstract Pre-biopsy genomic testing is used by providers to non-invasively rule out melanoma in uncertain pigmented lesions.1,2 Since melanoma is rare in children, validation studies for the test excluded pediatric patients.1-3 However, pigmented lesions with concerning clinical features are not uncommon in children, in which biopsies can be particularly challenging to perform.3 The noninvasive nature of genomic testing is attractive for facilitating selection of the subset of pediatric lesions that are appropriate for biopsy. The test consists of the Pigmented Lesion Assay (PLA), which detects RNA gene expression of LINC00518 (LINC) and PRAME, and an add-on assay for DNA promoter mutations in TERT, which is performed if ordered and if sufficient genomic material is available. The test is positive if one or more genomic markers are detected.1,2 The objective of this analysis was to compare genomic biomarker results between uncertain pigmented lesions from adult and pediatric patients. Methods Between May and October 2022, skin samples were collected using adhesive patches and submitted, along with patient age and anatomic location of the lesion, to the clinical lab for genomic profiling. Samples were assessed for LINC00518 and PRAME RNA (qPCR), and in cases with sufficient material, DNA mutations in the TERT promoter region (Sanger sequencing). Deidentified samples were categorized by anatomic location (head/neck, trunk, or extremities) and age (pediatric: <18 years, adult: ≥18 years). Positivity rates for the PLA (and each individual marker) and the TERT add-on assay were calculated and compared between adult and pediatric samples. Results In total, 34,050 adult and 2,327 pediatric samples underwent PLA analysis. Anatomic locations of the lesions tested were similar between age groups, with the lesions on the trunk accounting for just over 50% of lesions tested (Table 1). Introduction and Objective Table 1. The anatomic locations of 5 samples (4 adult, 1 pediatric) were not specific enough to be assigned to a category. Adult (≥18 years) N=34,046 Pediatric (<18 years) N=2,326 Anatomic Location n % n % Trunk 17,921 52.6% 1,265 54.4% Extremities 8,432 24.8% 554 23.8% Head and Neck 7,693 22.6% 507 21.8% Overall positivity rates for the PLA were similar between adult (7.0%, n=2,393) and pediatric (8.0%, n=187) samples. Of PLA-positive samples, the proportion positive for LINC alone was higher in pediatric samples (69.5%) compared to adult samples (31.4%) (Table 2). The TERT add-on assay was performed on 11,084 adult and 613 pediatric samples. TERT mutations were detected in 7.5% of adult and 0.5% of pediatric samples (Table 3). Adult (≥18 years) N=34,050 Pediatric (<18 years) N=2,327 PLA Results n % n % Negative 31,657 93.0% 2,140 92.0% Positive 2,393 7.0% 187 8.0% LINC Only 752 31.4% 130 69.5% PRAME Only 1,090 45.5% 27 14.4% LINC and PRAME 551 23.0% 30 16.0% Table 2. Adult (≥18 years) N=11,084 Pediatric (<18 years) N=613 TERT Results n % n % Negative 10,254 92.5% 610 99.5% Positive 830 7.5% 3 0.5% TERT Only 616 74.2% 1 33.3% LINC, PRAME, TERT 120 14.5% 1 33.3% PRAME, TERT 66 8.0% 0 0.0% LINC, TERT 28 3.4% 1 33.3% Table 3. Slide Number 1