PowerPoint Presentation Appropriate utilization of the prognostic 40-gene expression profile (40-GEP) test for cutaneous squamous cell carcinoma (cSCC) demonstrated by clinical reports and physician evaluation of real-world cases Acknowledgments & Disclosures References › This study was sponsored by Castle Biosciences, Inc. › All authors contributed to and approved the presentation. › JS, BR, AF, SK and RC are employees and shareholders of Castle Biosciences, Inc. 1. Karia, et al. JAAD 2012 2. Cañueto et al. JAAD 2019 3. Ruiz et al. JAMA Dermatol 2019 4. Wysong, et al. JAAD 2021 5. Ibrahim, et al. Future Oncology 2021 Presented at Winter Clinical Dermatology Conference; January 14-19, 2022. Aaron S. Farberg1, Jennifer J. Siegel2, Briana Rackley2, Alison L. Fitzgerald2, Sarah J. Kurley2, Robert W. Cook2 1Baylor Scott & White Health System; 2Castle Biosciences, Inc. For more information: aaron.farberg@gmail.com ›Summary metrics from one year of clinical orders of the 40-GEP test demonstrate that clinicians are ordering the test for the intended use population ›Survey findings revealed that when incorporating 40-GEP testing into their decision-making process for high-risk cSCC patients, clinicians do so in a risk-aligned manner ›These results indicate that the additional information provided by the 40-GEP test can appropriately assist in management decisions when included with traditional risk factor assessment. Conclusions Methods Objective › To evaluate appropriate utilization of the 40-GEP via analysis of a clinician survey, in which real-world cases submitted for clinical testing were presented with or without 40-GEP test results. › To evaluate demographics of clinicians and usage of the 40-GEP test from one year of clinical orders. › Six real-world cases, representing the spectrum of those submitted for clinical testing, were presented to 40-GEP test users (10+ orders/year minimum), first without 40-GEP result (pre-test) and then with 40-GEP results (post-test). › Clinicians were asked what treatment recommendations they would make for each pre- and post-test patient case. Assessments from the 34 responding clinicians were ordinally scored and compared using Wilcoxon Rank or Kruskal-Wallis. › Summary metrics on the 2515 samples received during the first year of clinical ordering (August 31, 2020– August 31, 2021) that met clinical testing criteria, including 40% tumor content and sufficient RNA, were generated. › The 40-GEP Class call and patient risk factors were captured by clinical requisition form review. Risk factors included lesion located on the H or M area, ≥2cm diameter, poorly defined borders, patient immunosuppression, rapidly growing tumor, site of prior RT or chronic inflammation, History & Physical- other factor noted, high-risk subtype, Clark Level IV, >2mm invasion, poorly differentiated, LVI, PNI, invasion beyond the subcutaneous fat. Results › Clinicopathologic factors for the 6 real-world cases are shown in Table 1. Clinicians were well-aligned in their pre-test risk strategy levels among the real-world cases, despite randomization prior to presentation to clinicians (Figure 1). › Post-testing, clinicians’ overall management plan intensity was significantly changed depending on GEP prognostic risk (Figure 2A). Recommendations for specific treatment decisions were altered depending on 40-GEP result (Figure 2B-D). Asterisks indicate significant change from baseline, corrected for family- wise error, p<0.016). › 40-GEP testing resulted in 68.8% Class 1, 28.3% Class 2A, 2.9% Class 2B primary SCC lesions (Figure 3A). Of the n=2515 samples meeting clinical testing criteria, 98.1% generated successful test results (n=2468 Class call; n= 47 multigene failures) (Figure 3B). 75.3% of clinically tested samples have 2 or more high risk factors (median = 3, average = 2.8) (Figure 3C). The cases submitted for testing align with the intended use population with almost all cases classifying as NCCN high or very high risk (Figure 3D). Synopsis › There has been an unprecedented increase in cSCC incidence over the past three decades,1 along with a continued discordance between available staging systems.2,3 › The 40-GEP test was developed and validated to augment traditional assessment approaches with the intention to improve risk-directed patient management for high-risk cSCC patients with one or more risk factors. › The 40-GEP test has shown significant metastatic risk stratification independent of clinicopathologic factors and staging systems using these factors.4,5 Figure 1. Pre-test overall management intensity by case Real-World Case Clinical Impact Study Case Age Sex Location Subtype Differentiation Additional high-risk factors High 81 ♂ L superior medial forehead NR Moderate Invasion beyond subcutaneous fat, PNI, LVI, ≥2 cm Moderate High 86 ♂ R cheek Infil Poor Invasion >2 mm Moderate Low 75 ♀ R temporal scalp Infil Poor Low.1 75 IS* ♂ R mid preauricular cheek Acan Moderate Low.2 69 ♀ R inferior postauricular skin Infil Moderate Lowest 71 ♀ R dorsal hand (rapidly growing) NR Moderate PNI = perineural invasion; LVI = lymphovascular invasion; NR = not reported; Infil = infiltrating; Acan = acantholytic *IS = immunosuppressed Case Table 1. Clinicopathologic risk factors for six real-world cases High Moderate Low Overall Management Intensity Scan here for more info Figure 2. 40-GEP impacts clinician management planning in real-world patient scenarios Overall Management Intensity StrategyA) B) C) D) Baseline Class 1 Class 2A Class 2B Adjuvant Radiation Therapy ** ** *** ** **** * * ***** **** *** * ***** **** ** Frequency of Follow-up (3 years) Nodal Assessment via Imaging * ***** **** *** Real-World Clinical Testing Experience 40-GEP Testing • Samples passing quality control and reporting a Class call • n=2468 SCCs from n=2402 patients • 56 and 5 patients had 2 or 3 lesions tested, respectively. 68.8% Class 1 28.3% Class 2A 2.9% Class 2B Primary cSCC with qualifying high-risk factor reported Figure 3A. Molecular risk profile of patients tested during first year of clinical availability of 40-GEP Figure 3C. Most tested patients have 2 or more high risk factors Figure 3B. The 40-GEP test has high technical reliability Figure 3D. Clinicopathologic risk group of tested patients 98.1% Successful 40-GEP 1.9% MGF Clinicopathologic Risk* % of Patients NCCN: Very High Risk 39.3% High Risk 60.5% Low Risk** 0.2% BWH T-stage: T1 38.5% T2a 39.4% T2b 21.6% T3 0.6% *Estimated based on factors reported. All reported PNI was considered an upstaging factor. For patients with >1 lesion tested, the riskiest lesion is reported here. **All patients designated low risk by NCCN presented with infiltrating histopathology. Risk factor count per sample N u m b e r o f sa m p le s Median = 3 Average = 2.8 https://castlebiosciences.com/research-development/publications/ Slide Number 1