DecisionDx-Melanoma Test for Cutaneous Melanoma Validated in Two Prospective Multicenter Study Cohorts to Provide Guidance for Sentinel Lymph Node Biopsy Recommendations

Validation data from 1,421 patients presented in Late-Breaking Research session at the 2018 AAD Annual Meeting

SAN DIEGO--(BUSINESS WIRE)--Castle Biosciences, Inc., a provider of molecular diagnostics to improve cancer treatment decisions, today announced the presentation of a study highlighting research on a new clinical use for the DecisionDx^®-Melanoma gene expression profile test to guide sentinel lymph node biopsy (SLNB) recommendations. The study titled, “A Prospective Multicenter Study to Evaluate the Clinical Impact of a 31-Gene Expression Profile Test on Physician Recommendations for Management of Melanoma Patients,” (Abstract 6805) will be presented during the Late-Breaking Research: Basic Science/Cutaneous Oncology/Pathology session of the 74^th Annual Meeting of the American Academy of Dermatology (AAD), held in San Diego, CA from February 16-18.

The study found that the DecisionDx-Melanoma test result, along with tumor thickness and age, can inform recommendations for SLNB in line with national melanoma clinical practice guidelines.

Study Background:

• Current National Comprehensive Cancer Network (NCCN) melanoma guidelines (v2.2018) provide recommendations for SLNB based on patients’ likelihood of SLN positivity. The NCCN recommends that clinicians “discuss and offer” SLNB if a patient has a greater than 10% likelihood of SLN positivity, “discuss and consider” if a patient has a 5 to 10% likelihood of SLN positivity and “does not recommend” SLNB if a patient has a less than 5% likelihood of SLN positivity.
• Risk for SLN positivity has been established through traditional clinicopathologic features such as Breslow’s thickness and ulceration status. Importantly, older patients (≥55 years old and increasing with age) are at a higher risk of recurrence and death from melanoma but a lower likelihood of SLN positivity.
• The DecisionDx-Melanoma test is a 31-gene expression profile test which uses tumor biology to provide an individual risk of recurrence in cutaneous melanoma patients. The validity and performance of the test has been confirmed in three multicenter archival tissue studies involving 690 patients and three prospective studies involving 702 patients. The test has been shown to be an independent predictor of recurrence compared to clinicopathologic factors of Breslow’s thickness, ulceration status, mitotic rate and SLN status.
• This study was designed to determine whether the test could improve identification of patients at a low likelihood of SLN positivity (<5%) as well as those at a higher likelihood (>10%) alone or in combination with clinicopathologic factors.

Key Study Findings:

• Using an algorithm that was developed in a retrospective cohort of 946 patients, the DecisionDx-Melanoma test result along with clinicopathologic factors achieved validation in two independent, prospective, multicenter cohorts totaling 1,421 consecutively tested patients from 26 U.S. surgical oncology, medical oncology and dermatologic practices.
• For patients with T1-T2 tumors who had a Class 1A test result (lowest risk of recurrence), SLN positivity was 4.6% for all ages, 2.8% in patients ≥55 years old and 1.6% in patients ≥65 years old.
• For patients with T1-T2 tumors who had a Class 2B test result (highest risk of recurrence), SLN positivity was 18.8% for all ages, 16.4% in patients ≥55 years old and 11.9% in patients ≥65 years old.
• The impact of not performing SLN biopsy in Class 1A patients was evaluated based on a retrospective dataset of 690 patients with long-term follow-up. At 5 years, Class 1A patients with T1-T2 tumors had a melanoma specific survival of 99.6%, overall survival of 98.2%, and distant metastasis-free survival of 95.3%.
• The incorporation of tumor biology, assessed by the DecisionDx-Melanoma test, in the evaluation of SLN positivity risk, helped identify a group of patients with T1-T2 tumors that have a <5% likelihood of a positive SLN, a risk group that is not recommended for SLNB based on current guidelines.

“SLN biopsy is an important staging factor in the work-up of cutaneous melanoma patients. However, use of SLN in older patients poses a challenge in balancing the benefits of identification of microscopic Stage III disease versus the risk of an operation,” said study co-author John Vetto, M.D., Professor of Surgery, Division of Surgical Oncology and Director of the Cutaneous Oncology Program at the Department of Surgery, Oregon Health & Science University. “The validation of the DecisionDx-Melanoma test to inform SLNB decisions offers an important additional use of this test to guide management in early stage melanoma patients.”

About DecisionDx-Melanoma

The DecisionDx-Melanoma test uses tumor biology to provide a prediction of individual risk of melanoma recurrence beyond traditional factors. Using tissue from the primary melanoma, the test measures the expression of 31 genes. The test has been validated in three multicenter studies that have included 690 patients and have demonstrated consistent results. Performance has also been confirmed in four prospective studies including 702 patients. The consistent high performance and accuracy demonstrated in these studies, which combined have included over 1300 patients, provides confidence in disease management plans that incorporate DecisionDx-Melanoma test results. Prediction of the likelihood of sentinel lymph node positivity has also been validated in two prospective multicenter studies which included over 1400 patients. Clinical impact has been demonstrated in multicenter and single-center studies showing that test results change approximately 50% of management decisions. More information about the test and disease can be found at www.SkinMelanoma.com.

About Castle Biosciences

Castle Biosciences is a molecular diagnostics company dedicated to helping patients and their physicians make the best possible decisions about their treatment and follow up care based on the individual molecular signature of their tumor. The Company currently offers tests for patients with cutaneous melanoma (DecisionDx^®-Melanoma; www.SkinMelanoma.com) and uveal melanoma (DecisionDx^®-UM, DecisionDx^®-PRAME and DecisionDx^®-UMSeq; www.MyUvealMelanoma.com), with development programs in other underserved cancers. Castle Biosciences is based in Friendswood, TX (Houston), and has laboratory operations in Phoenix, AZ. More information can be found at www.CastleBiosciences.com.

DecisionDx-Melanoma, DecisionDx-UM, DecisionDx-PRAME and DecisionDx-UMSeq are the trademarks of Castle Biosciences, Inc. Any other trademarks are the property of their respective owners.